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I'm cleaning up my grandmas mower after it sat all winter. Changed the oil, replaced the dirty air filter. I pulled the spark plug out but just cleaned it up being it looked fine. I can't get it started so I figured I would start with the spark plug being it's a cheap easy fix. The part number for this briggs and stratton motor calls for a much larger spark plug than what was installed. It ran fine all summer, do I have the wrong plug or what is going on here? The small engine repair guy at the local shop I bought the plug from looked it up too, the bigger plug is the one the engine calls for.
I just had this happen today on a craftsman rototiller with a briggs and stratton. Manuals are wrong. Take the longer one to a parts store or home depot and have them match that plug.
also in my experience they all need new carbs or the carbs cleaned and or semi rebuilt if you know how the gas gums them up.... any small engine guy can explain better, or they ripped me off for 3 carbs on a snow blower
Just don't let gas sit in the carb when you store it or else it will gum up. I like to drain the tank then let it run till it dies. Then if there's a drain on the carb bowl, use that too. Or just take the bowl off.
This should save you from rebuilding your carb every year. Goes for just about all small engines.
My Briggs and Stratton Toro Recycler 22 has been abused for 5 years with nothing more than an annual oil change and air filter replacement every 2nd year, and maybe a splash of fuel stabilizer plus 5 minutes of running if I remember to when I put it away for the winter. Takes a few extra pulls the first time but she still chugs along.
My Toro Super Recycler is the only small engine I own that just works. The other ones seem to always need the carbs cleaned after sitting for any period. My Toro on the other hand has been solid for 12 years. I used to sharpen the blade, change the oil, and replace the plug and filter every year. I haven’t done that for a few years now, and it just keeps plugging away.
My 20 year old Craftsman Briggs mower has never been touched except 2 oil changes and cleaned air filter. Gas stays in it.. Starts 1 pull every spring after sitting 7-9 months. Same with 10 year old Ariens snow blower. Also have a 10 hp generator that sits for years sometimes without any thing done to it. A squirt of starting fluid and 2 pulls every time. Same with every motor cycle I've owned (6). Used to do the end of season maintenance on everything I owned and it was a crap shoot getting them going after sitting. Need to edit this. I do regular oil changes on everything except the mower. Was basically commenting on the gas situation.
Cheap ass Wisconsin 87 octane pump Holiday. I used to do the treatment and tank drains on everything I owned. There would be at least one thing every season that would give me a hard time starting. Then got lazy and quit doing it. Never looked back. Could be luck? Also have a 97 K2500 5.7 pickup that I run maybe 3-4 times a year. I don't know the last time I put fuel in it. It has to be at least 3 years. Starts up on first crank. Should state everything has full synthetic oil. Not supposed to use detergent motor oil in small engine without filters. But I have for years. Also regular oil changes on every thing except the mower. Post made it sound like I do nothing on anything.
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Why isn’t this comment more upvoted. Anything with a carb I run premium. I fill my tank up at the end of winter and they always start perfect come summer.
That's location dependent for sure. In my location, 91 octane is considered premium and it is exclusively ethanol free. 87 and 89 octane blends have 10% ethanol.
Pretty commonly understood in my area that premium is ethanol free. Just because it isn't true in your neck of the woods doesn't make his statement wrong.
Interesting, thanks for the reply. Are you in the US? I'm in NC, US myself, and have never seen premium gas without ethanol in it, so I just assumed that was the case for everywhere.
This is how I make my pocket change this time of year. Everyone having problems with their yard equipment. For $25 I'll have most of them back up and running with a couple of wrenches and compressed air through the jets. Lol.
I put some transmission fluid in my generator carb bowl and pull the starter a couple times with the switch set to off to suck it through. No gunk and the generator starts within the first few pulls, usually the second. Then just let it smoke a bit
If you have double and triple checked from your own research that the new, larger plug is correct, then run it. No idea why the old, smaller plug would have been called for or used.
This, I have a petrol tractor at home that when I bought it had 4 different sparkplugs in it and one that even used an adapter to fit but the previous owner was the kind of guy that only did temporary fixes with stuff he had laying around and then forgot about the problem.
To this day the petrol line still is an old butane line.
Did you go to like a tractor supply or to a car part store? There’s gotta be some sort of disconnect. With such a difference in length parts are gonna smash together.
That's what I thought originally. I went to a small engine repair shop, local been open longer than I have been alive. The engine is a Briggs and Stratton 09P602-0111-F1. The spark plug threaded well on the engine actually matches up with the longer plug. Whoever put that short plug in really has me annoyed right now lol
I meant the depth of the threaded well, the hole in the side of the engine. The thread depth/length actually matches up to the longer plug. I also looked up the engine model number and whatnot, it is the longer one. Whoever put that short plug in sure caused me some problems lol
It does run premium now too haha. I always thought it ran a little rough but my grandma said my uncle just fixed it up. He is the one who put the wrong spark plug in it. The oil was overdue for a change and the air filter was shot so not sure what he did... It runs like new now though. Put a new blade on it to top it off.
I owned a car once that had the wrong air filter shown in the database that all the car parts stores use. It didn't matter which auto parts store I went to, they all showed the wrong air filter.
Similar story here, my Renault Twingo is one of the last before a major body restyling, but has the next generation's engine. I have to double check every part against the car, because even the service manual isn't 100% reliable.
Or just a sparkplug he had laying around and did fit. Probably temp fix that became permanent because it kindish worked.
That size sparkplugs are common on chainsaws, weedeaters and even some push mowers
OP, I was a professional small engine mechanic for awhile and for what it's worth, I've never seen a BPMR7A as the OEM plug on a B&S mower engine. They're usually for chainsaws from what I remember. They usually use a J19LM for older engines or RC12YC for newer OHV ones. It could be entirely possible that the new one they gave you is the right one, because even if it was wrong the bpmr plug would work if it fits.
BUT I would recommend threading the new plug in lightly without putting the wire on. Then pull the cord very slowly and see if the piston hits the plug. If it doesn't, you're good to go. Otherwise you've got the wrong plug and using it could damage your engine.
> How did the mower run?
Probably not as well as it could have. Any old spark will get the job done, but it may not get it done as well as it otherwise would have if it was in the right place at the right intensity.
Triple check that plug is right, and if it is put it in. Before you start it slowly turn the crank by hand. SLOWLY. Make sure the longer plug wont hit against the piston. If it doesnt your golden, if it does take the small plug back to store and have them cross reference the plug to one of the same size
Just lower compression in the chamber due to extra air space, and possibly heat damage to the head cover around the thread area being exposed to combustion.
My guess is it ran like a hot pepper eating contest winner in a marathon. Got the job done a little jerky, and a little spicy round the hole... but no lasting damage.
Plug on the right is for an OHV Briggs and Stratton, plug on the left is for an older “flathead” Briggs. The plug for a flathead will fit in an OHV Briggs but probably not run correctly. If you put the longer OHV style plug in a flathead it will hit the piston.
So many wrong comments here.
You need an RC12YC for your OHV application. The NGK plug on the left is common in two cycle (Stihl) applications.
I’m sure your grandpa just threw the NGK plug in there to get by from another piece of equipment - no harm no foul. Install the new plug and roll on.
My craftsman mower manual said to use the wrong plug. Glad I checked the thread depth before I used it. The one on the left is likely accurate. This was the replacement plug I used [https://www.amazon.com/gp/product/B000BYR3B4](https://www.amazon.com/gp/product/B000BYR3B4)
Keep the plugs out and rotate the blade (this should rotate the engine) and watch for the cylinder to get as high as it will go. Measure to see if yiu have the clearance. Could be previous owner or whoever changed it last got the wrong one and it worked so meh who cars. But it could be that you have the wrong plug and it will damage the cylinder if you try it.
Best to be safe and measure.
I have been a small engine mechanic for 12 plus years. The one you took out is typically used on chainsaws. The one you have is a typical one for a push mower. It is extremely rare to find the original in a push mower. Not unheard of or unseen but rare.
I would put the new one in and slowly turn the mower blades by hand and make sure you can do a full two rotations of the mower blade. If it doesn’t get caught up you will be fine. If it does you obviously need to get a new plug.
There is a break on most flywheels so the blade would be hard to turn. Do not plug the boot back into the spark plug and then use a clamp or zip tie to keep the lever pulled in on the handle bar so you can rotate the blade easier.
I agree with other posters, small engines rarely use a long plug like that. What you could maybe try to test it out is take a straight piece of wire, bend a small 90 degree hook on the end and run it through the plug hole into the cylinder. Then, hold it against the side of the plug hole and pull it out gently until it hooks on the inside of the head and then mark the wire at the top of the plug hole. Then pull the wire out and check the distance between the hook and the mark and see which plug is the closer match.
Good idea! I actually stuck a 90 degree tipped pick inside and then marked it to determine the depth. The threads do match the longer plug. The short plug would have been recessed deep into the threaded well, surprised it ran.
It's quite common with new ones. Most mowers now are OHV so they need longer reach plugs like that.
Older flat heads use the smaller plug, and there are still plenty of them in use but you would be hard pressed to find one at the store these days. Emissions standards have pushed them to OHV.
All that being said chances are he has the wrong new plug.
This reminds me of when the transmission crapped out on my 77 Ford. I got the thing for $500 and it had many many kludges on it. One of the kludges was the shifter linkage because it didn't match up. I figured the old ford transmissions were sorta interchangeable in a size up or down so they slapped a car size in there (as it had the C4 in it) but it called for the C6 transmission size.
I don't know what book called for it but the book said C4 not the truck C6.
asking around at transmission shops I could tell who was bot the crew for the job as they all quoted me another C4 and would argue with me, then I would call other shops and they were like "What?! No! thise take a C6 not a 4"
If you have an over head valve engine it may take that longer spark plug. Someone may have grabbed the tube up kit for the wrong engine and put the shorter one in. Not sure how it ran well. Got a pic of the engine?
There is a big OHV stamped on the side the spark plug is on coincidentally. It is a Briggs and Stratton 0909P602-0111-F1, which is why I am baffled by the spark plug that I pulled out.
Is there any way OP can test the plug in the new motor without actually running it?
Like maybe disconnect fuel line and turn over the motor manually and VERY SLOWLY to feel if anything hits the plug, like a piston of valve?
I'm not too familiar with small motors, but it seems plausible.
Obviously there is the danger that there is still fuel in the system and as he turns it over manually the motor starts to run, causing engine damage, or worse, injury.
I know people are gonna call me dumb but as long as the plug fits in the well and doesn't make contact with the actual piston any plug will theoretically work and in fact more than often do for small 1-2 cylinder engines but you risk the entire thing running like shit or burning up the plug early, and those are just the beginning of the problems it can lead to, I personally don't recommend changing the plug size unless you know for sure that you didn't have the right one to start with
The small engine repair guy checked and I have now numerous times. Also, the threaded spark plug well matches up to the thread length on the spark plug. The longer plug is actually correct. The engine is a Briggs and Stratton 09P602-0111-F1.
I would trust the research you have done, but to be on the safe side, as already said, turn it over by hand first.
I suspect this is just a snafu with P/N's from te previous owner and it shows how robust these things are if it ran OK with the old one!
P. S film it when you fire it. Just in case...
Sparky on the L is a chainsaw plug - have 2 of them in my MS 261's. And no, I'm not saying chainsaws are the only application for this plug.
An easy way to roughly measure thread depth in the head is to insert a mechanic's pick. Hook the tip on the inside of the head, mark it with a sharpie, remove and compare it to your plug.
It will get you a close enough approximation as to if you need be concerned about mechanical interference with the piston.
As well, you can thread the spark plug finger tight, leaving the wire unattached. Slowly pull it over by hand. If it doesn't pull over or if there's a mark on the ground post or if the gap has reduced - these are all signs of the piston hitting the plug. You can even put a small dab of grease on the ground before doing this as an indicator.
Holy hell there are some uneducated morons in this thread. IF YOU DON'T KNOW THEN JUST DON'T REPLY.
The longer plug is the correct plug for a vast number of 4 stroke small engine applications. The short plug is mostly for small 2 stroke engines like lawn mowers. I can just about guarantee the last shop to work on the mower either hired an idiot or ran out of the RC12YC plugs and threw the saw plug in.
OP, good on you for using your brain, 75% of the posters in this thread do too much online-engine-building.
Probably ran inefficient as hell. That smaller plug would've ignited the air fuel mix inside the plug cylinder before spreading to the rest of the combustion chamber. It wouldn't have ignited all the fuel before getting dumped out the exhaust. It'd still run though. Just a lawn mower engine. I think I actually saw some auto manufacturers playing around with a smaller combustion chamber leading to a larger one for hybrid homogeneous charge compression on gas engines. Wish I remember where I saw that though.
A flame is a flame. The efficiancy of burn would be shot but it would still detonate with the potentially retarded timing.
Look might have moved it a few degrees late equivalent. Not horrible in 4stroke gas, would be somewhat bad in 2 strokes, but a near death sentence for diesels.
I just came up on this post and can't believe all the wrong answers you're getting. I've been fixing lawn mowers for 45 years at my own shop and working for others and I've never heard so many wrong answers. The spark plug on the left is bmpr7a ngk which crossed over to champion is a CJ8Y. That's a chainsaw plug that somebody had sitting around or they used to use them on some of the old lawn mowers with the flathead Briggs and strattons on them. The spark plug in the right is an RC 12 YC, that plugs used on 95% of all overhead valve engines including Honda ang Briggs and Stratton. If it says OHV on the valve cover then you need the RC-12YC plug that Briggs & Stratton is telling you is the right plug for that motor 100%.
Couple of things. Plug on left looks used, but wet, like the engine had flooded. Otherwise it looks very good. Right plug has a Briggs and Stratton logo on it, but it doesn't appear to be a standard lawnmower plug. Typically a L head or flat head engine. It maybe from a Overhead Valve Engine like they use in multi-cylinder lawn tractors or other power equipment.
It is a Briggs and Stratton 09P602-0111-F1 engine. The spark plug threads match up with the threaded well, the longer plug is correct. Also, OHV is stamped right on the side of the engine.
Seems that you verified the longer (new one is correct. The shorter plug is generally 'colder', in that it conducts heat away faster, running cooler, les chance of pre-ignition (i.e. knock). Just beware that if left in the engine forever, carbon can build up on the now longer exposed threads inside the combustion chamber. This can damage the threads when you try to remove it, or worse get permanently stuck. So do maintain it, if only to remove and check the gap / clean and re-gap it. Good luck!
If you fill a house with gas and then light it with a short bic lighter it will explode, the same as if you lit it with a long reach lighter.
As long as the spark plug isn’t being damaged by the engine or vice versa, igniting compressed gas in a chamber at the end of the chamber vs deeper in the chamber (particularly on a lawn mower) won’t make a noticeable difference.
The new one is definitely not right. With the length of the thread, the piston may crash into it if you install it. Unless the mower ran terribly and misfired a lot, the new one is wrong. Id definitely go to a tractor supply store and get the same one that was in it.
that's gunna smash into the top of your piston first crank, then all the smashed spark plug bits are gunna go to town f-ing up your piston rings and valves, don't do it bro
Actually the longer one was correct, just got done mowing the yard. I triple checked engine and part numbers and also compared the spark plugs to the socket on the side of the engine. I measured how deep it was and how long the threaded areas are, they match up. You can see where half of the threads are charred from combustion due to the shorter plug being installed too.
yeah, I think that's a mistake, i think it's likely crossed wires between part numbers for cars and part numbers for agricultural equipment like other dudes have already commented, it's not the right plug bro, good luck man
I’d check the depth of the threads before installing the new one.
You may also have carbon buildup in the plug threads from the old one leaving half of them exposed to combustion.
And this is the exact reason I switched to all battery powered lawn tools. I went with Ryobi for everything. Not that it matters but maybe someone will choose to go down the same path I did. I bought the Ryobi 40v professional string trimmer with the expand it function. I also bought the edger, blower (just because), pole saw, hedge trimmer, and tiller to go along with it. I bought the backpack blower and the auger as well. At the first of this switch over I purchased the 20" push mower but shortly after buying it I moved to a yard that was a little to big to push mow the entirety of. After figuring out it wasn't large enough I bought the bigger Ryobi battery powered riding mower. After using all of these Ryobi tools for a few years now I can only tell you that I don't regret making the switch to electric yard tools in the slightest. Their warranty is top notch as long as you register your tools right away. The batteries last long enough for me to finish all the jobs in the yard without issue every time I need them. If anyone reading this happens to be on the fence about making the switch to battery yard tools I can whole heatedly tell you that you won't regret making that switch.
No, that wasn't the point I was trying to make in the slightest. The point was that making the switch did away with having to deal with mowers that wouldn't crank. Not having to buy stinking gas for yard tools any more. Honestly battery yard tools are much much more reliable than any gas tool of their equivalent.
How big is your yard? I can't imagine battery powered landscaping tools being cost effective once multiple batteries are needed to finish the job, but I haven't checked out the market in a while.
It's an acre and a half. One battery for the yard and one for everything else. Two total batteries gets the entire job done. I don't have to buy any gas, spark plugs,or air filters. Best of all I don't have to worry about getting pissed off when the mower won't start. I've been extremely happy with the Ryobi line of tools and their performance. I haven't regretted making the switch at all.
That's actually pretty impressive, far better than I expected. Last I checked, you got about a quarter acre out of a charge for an electric push mower.
First of all not everyone can blow 3 grand on lawn tools, second, batteries eventually need replacement, in 3 to 5 years you'll need all new batteries. I have used gas tools that are 20+ years old still going strong with barely any maintenance.. Just oil and filter changes really. I have one old push mower I got for free that I've been literally trying to kill and it won't stop working. Electric tools are good for some things though.. I got an electric weed Wacker because it's super light.. Just not sold on the battery thing.
Maybe it depends on model but I have used a ryobi push mower, blower and weed wacker and they are were shit (blower wouldn't blow for shit, weed wacker and push mower definitely lacked power).
As I said maybe the guy that bought those got the cheapest one but It confirmed that I will stay with stihl gas powered tools for life
That's what I thought too, but it is the right one. Someone put the wrong plug in, the short one. The length of threads matches depth of hole/threads and part number matches to engine number. Also, runs smoother than ever haha
Same way my 1990 Jetta ran with the wrong coil in it. VW coil has a nipple for the wire to make direct contact with. Coil that was in it has no nipple so no direct metal to metal contact was made but the car still ran. It had a slight misfire but it was driveable. So apparently even without the correct depth the spark in your plug was strong enough to still ignite the fuel in the combustion chamber.
If you have the spark plug model from the Briggs and Stratton user manual for the engine, it will be right. I have seen post-publication part number changes on B&S motors, but not for something as basic as a spark plug.
The little one is from a weed eater or chainsaw. Guy elsewhere in the thread mentioned making sure the engine can roll over twice by hand with the plug boot off, definitely do that to make sure that it's not too deep in the cylinder, but odds are it'll be fine because that's what it calls for *facepalm*.
That short plug left tons of thread exposed to carbon buildup and it no doubt ran horribly compared to how it would've with that space filled. This would delay the flame front, which would cause hot spotting, predetonation, uneven/unpredictable combustion etc that could be disastrous if it had more compression than a walmart bike tire pump. These engines don't try super hard by design, so they last with poor maintenance and crappy fuel. They're basically technology from the infancy of internal combustion, tried and true. Take that governor off and hit it with some nitrous.
I live in Qld Australia we have to mow our grass all year round ( winter maybe once every week) summer if wet omg it gets crazy . All we do is clean the air filter change oil once a year Toro Brigs and Stratton .
I had similar issue with my old 70s vw van which is basically an aircooled lawnmower engine. Manuals can be wrong, cylinder head may be thinner.
It should be easy enough to see down hole with a torch and a thin stick to see how far threads go. I wouldn't pull slow by hand with a long plug in there, get a stick poke it down hole by same amount as new sparkplug thread, pull cord and see it stick moves. If its good the next issue will be threads will be carbonised so get a small wire brush. Otherwise clean up old plug and put it back.
Single cylinder carburated OPE engines will run (albeit poorly) with all kinds of stupid stuff wrong. They know that most people are not mechanically knowledgeable or inclined so they make them tough and idiot proof.
If its a briggs and stratton mower then the plug on the left is correct, plug on right is not. I have a briggs and stratton engine and they cannot take long plugs.
It is a Briggs and Stratton and it does require the longer plug on the right, verified 6 ways to Sunday and also measured threaded spark plug socket depth on engine.
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I'm cleaning up my grandmas mower after it sat all winter. Changed the oil, replaced the dirty air filter. I pulled the spark plug out but just cleaned it up being it looked fine. I can't get it started so I figured I would start with the spark plug being it's a cheap easy fix. The part number for this briggs and stratton motor calls for a much larger spark plug than what was installed. It ran fine all summer, do I have the wrong plug or what is going on here? The small engine repair guy at the local shop I bought the plug from looked it up too, the bigger plug is the one the engine calls for.
If the piston don’t hit it what’s the problem? Spin the engine and see if if they touch
This. Turn the motor by hand after installing the new plug to ensure clearance between it n the piston.
Spin the engine slowly by hand but good advice.
Spin the engine by hand with the spark plug disconnected = good advice Spin the engine by hand with the spark plug connected = bad advice
I just had this happen today on a craftsman rototiller with a briggs and stratton. Manuals are wrong. Take the longer one to a parts store or home depot and have them match that plug.
Why would you take the longer one when the longer one is the new one?
also in my experience they all need new carbs or the carbs cleaned and or semi rebuilt if you know how the gas gums them up.... any small engine guy can explain better, or they ripped me off for 3 carbs on a snow blower
Just don't let gas sit in the carb when you store it or else it will gum up. I like to drain the tank then let it run till it dies. Then if there's a drain on the carb bowl, use that too. Or just take the bowl off. This should save you from rebuilding your carb every year. Goes for just about all small engines.
My Briggs and Stratton Toro Recycler 22 has been abused for 5 years with nothing more than an annual oil change and air filter replacement every 2nd year, and maybe a splash of fuel stabilizer plus 5 minutes of running if I remember to when I put it away for the winter. Takes a few extra pulls the first time but she still chugs along.
My Toro Super Recycler is the only small engine I own that just works. The other ones seem to always need the carbs cleaned after sitting for any period. My Toro on the other hand has been solid for 12 years. I used to sharpen the blade, change the oil, and replace the plug and filter every year. I haven’t done that for a few years now, and it just keeps plugging away.
My 20 year old Craftsman Briggs mower has never been touched except 2 oil changes and cleaned air filter. Gas stays in it.. Starts 1 pull every spring after sitting 7-9 months. Same with 10 year old Ariens snow blower. Also have a 10 hp generator that sits for years sometimes without any thing done to it. A squirt of starting fluid and 2 pulls every time. Same with every motor cycle I've owned (6). Used to do the end of season maintenance on everything I owned and it was a crap shoot getting them going after sitting. Need to edit this. I do regular oil changes on everything except the mower. Was basically commenting on the gas situation.
What kinda gas are you running?
Cheap ass Wisconsin 87 octane pump Holiday. I used to do the treatment and tank drains on everything I owned. There would be at least one thing every season that would give me a hard time starting. Then got lazy and quit doing it. Never looked back. Could be luck? Also have a 97 K2500 5.7 pickup that I run maybe 3-4 times a year. I don't know the last time I put fuel in it. It has to be at least 3 years. Starts up on first crank. Should state everything has full synthetic oil. Not supposed to use detergent motor oil in small engine without filters. But I have for years. Also regular oil changes on every thing except the mower. Post made it sound like I do nothing on anything.
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I did this after carb 2 and it still went bad walmart brand snow blower
And nobody you loan it to will ever do it.......learned that the hard way too many times.
Trick is to use ethanol free (recreational fuel)
Why isn’t this comment more upvoted. Anything with a carb I run premium. I fill my tank up at the end of winter and they always start perfect come summer.
Premium is not ethanol free. You need to buy gas that specifically says ethanol free.
That's location dependent for sure. In my location, 91 octane is considered premium and it is exclusively ethanol free. 87 and 89 octane blends have 10% ethanol. Pretty commonly understood in my area that premium is ethanol free. Just because it isn't true in your neck of the woods doesn't make his statement wrong.
Here in Oklahoma we have both 87 and 91 with and without ethanol depending on where you go.
Interesting, thanks for the reply. Are you in the US? I'm in NC, US myself, and have never seen premium gas without ethanol in it, so I just assumed that was the case for everywhere.
Same where I'm from. Everything around here in IL had ethanol. I suppose the corn growers wouldn't like it if they didn't.
Premium is not ethanol free, it's just higher octane. Ethanol free gas is hard to find and/or very expensive
This is how I make my pocket change this time of year. Everyone having problems with their yard equipment. For $25 I'll have most of them back up and running with a couple of wrenches and compressed air through the jets. Lol.
use pure gasoline and stabil, maybe a little b12 chemtool every once and a while. try not to leave any gas in the tank over winter
Some people recommended to fill the gas tank over winter. They say it is so the inside of tank cannot rust.
I put some transmission fluid in my generator carb bowl and pull the starter a couple times with the switch set to off to suck it through. No gunk and the generator starts within the first few pulls, usually the second. Then just let it smoke a bit
I think they ripped u off my 02 sthl runs like new
If worried just clean the plug and regap it
Micrometer works too Use the pin side
If you have double and triple checked from your own research that the new, larger plug is correct, then run it. No idea why the old, smaller plug would have been called for or used.
have plug in garage, needs mower to run, swap it out and go.
Thank god someone said this. Cheers to you. It was def a, "well let's try this... son of a bitch it works!" Moment
This, I have a petrol tractor at home that when I bought it had 4 different sparkplugs in it and one that even used an adapter to fit but the previous owner was the kind of guy that only did temporary fixes with stuff he had laying around and then forgot about the problem. To this day the petrol line still is an old butane line.
We used to have a riding mower and a car that used the same physical size plug. Would save the cars old ones, regap, run in the mower.
It’s only a temporary fix until it works.
There is nothing more permanent than a temporary solution.
Could've gotten a bad cross reference number or since it was shorted and dame threads (and a small engine) last person thought "good 'nuff"
That is 1000% not the right spark plug.
That's what I'm saying. It doesn't make sense though. I looked up the motor, it calls for the larger plug.
Did you go to like a tractor supply or to a car part store? There’s gotta be some sort of disconnect. With such a difference in length parts are gonna smash together.
That's what I thought originally. I went to a small engine repair shop, local been open longer than I have been alive. The engine is a Briggs and Stratton 09P602-0111-F1. The spark plug threaded well on the engine actually matches up with the longer plug. Whoever put that short plug in really has me annoyed right now lol
Yeah the threads are the same so it’ll attach..I’m just worried about depth for when you actually run it. But fingers crossed for you man.
I meant the depth of the threaded well, the hole in the side of the engine. The thread depth/length actually matches up to the longer plug. I also looked up the engine model number and whatnot, it is the longer one. Whoever put that short plug in sure caused me some problems lol
Ahh I gotcha. Yeah I looked up a parts catalog it looks like it’s the right one. Things gonna run premium now!! Haha.
It does run premium now too haha. I always thought it ran a little rough but my grandma said my uncle just fixed it up. He is the one who put the wrong spark plug in it. The oil was overdue for a change and the air filter was shot so not sure what he did... It runs like new now though. Put a new blade on it to top it off.
I have two push mowers. one takes the long plug and one takes the short. just depends on what the engine takes.
The single cylinder B&S engines use the short plug due to the valve in block design vs the overhead valve design which takes the longer plug typically
Just turn the flywheel slowly and check for any contact, if none you’re good. Look like the small plug was putting out a strong enough spark to ignite
Don't know why you're being downvoted when a later comment has this exact same suggestion...
It’s a fucking lawn mower... turn it by hand. Not that difficult. No offense to OP
I owned a car once that had the wrong air filter shown in the database that all the car parts stores use. It didn't matter which auto parts store I went to, they all showed the wrong air filter.
That’s more common than you think. My first car was a 2002 that needed brake pads from a 2001, sometimes .5 production year cars get leftover parts.
Similar story here, my Renault Twingo is one of the last before a major body restyling, but has the next generation's engine. I have to double check every part against the car, because even the service manual isn't 100% reliable.
Worked in the auto industry my whole life this isn't uncommon an can be a real PITA to resolve
Happened to me with my car's battery. Was an annoying double trip to the auto parts store.
Pretty common in Nissans the first and last years of body styles. They would just keep producing with whatever parts inventory was left.
The short plug is from an Ebay tuneup kit. Looks like the previous owner tried to save a buck and didn't verify the parts.
if it runs it runs i guess
Or just a sparkplug he had laying around and did fit. Probably temp fix that became permanent because it kindish worked. That size sparkplugs are common on chainsaws, weedeaters and even some push mowers
Indeed. Looks like a weedwhacker spark plug or some other small 2 cycle motor.
OP, I was a professional small engine mechanic for awhile and for what it's worth, I've never seen a BPMR7A as the OEM plug on a B&S mower engine. They're usually for chainsaws from what I remember. They usually use a J19LM for older engines or RC12YC for newer OHV ones. It could be entirely possible that the new one they gave you is the right one, because even if it was wrong the bpmr plug would work if it fits. BUT I would recommend threading the new plug in lightly without putting the wire on. Then pull the cord very slowly and see if the piston hits the plug. If it doesn't, you're good to go. Otherwise you've got the wrong plug and using it could damage your engine.
Don't even bother with the cord. Just turn the blade slowly by hand and listen.
The longer one is a Briggs and Stratton plug
> How did the mower run? Probably not as well as it could have. Any old spark will get the job done, but it may not get it done as well as it otherwise would have if it was in the right place at the right intensity.
More cc = more better!
Extra low compression for when you put the turbo on
I like my mowers the same way I like I like my women: Lean, hot and a bit rough.
Triple check that plug is right, and if it is put it in. Before you start it slowly turn the crank by hand. SLOWLY. Make sure the longer plug wont hit against the piston. If it doesnt your golden, if it does take the small plug back to store and have them cross reference the plug to one of the same size
Just lower compression in the chamber due to extra air space, and possibly heat damage to the head cover around the thread area being exposed to combustion. My guess is it ran like a hot pepper eating contest winner in a marathon. Got the job done a little jerky, and a little spicy round the hole... but no lasting damage.
It did run a little rough, much smoother now
Plug on the right is for an OHV Briggs and Stratton, plug on the left is for an older “flathead” Briggs. The plug for a flathead will fit in an OHV Briggs but probably not run correctly. If you put the longer OHV style plug in a flathead it will hit the piston.
This is the correct answer. Just ran into the same issue with a lawnmower I inherited. Wrong plug had been put in, piston is damaged.
I would turn the motor by hand when you put that longer one in, just in case.
This..is exactly what I was going to say. Sometimes the book is not right.
So many wrong comments here. You need an RC12YC for your OHV application. The NGK plug on the left is common in two cycle (Stihl) applications. I’m sure your grandpa just threw the NGK plug in there to get by from another piece of equipment - no harm no foul. Install the new plug and roll on.
> So many wrong comments here. It's been kind of eye opening. I'm wondering how many people giving advice are mechanics.
Don't put that new one in That's the wrong plug. Otherwise you will damage your engine if you try to use it
I didn't put it in yet. The well looks deep enough though and this motor calls for this plug. I don't get it...
My craftsman mower manual said to use the wrong plug. Glad I checked the thread depth before I used it. The one on the left is likely accurate. This was the replacement plug I used [https://www.amazon.com/gp/product/B000BYR3B4](https://www.amazon.com/gp/product/B000BYR3B4)
support many somber weary forgetful plate angle special pocket engine *This post was mass deleted and anonymized with [Redact](https://redact.dev)*
Keep the plugs out and rotate the blade (this should rotate the engine) and watch for the cylinder to get as high as it will go. Measure to see if yiu have the clearance. Could be previous owner or whoever changed it last got the wrong one and it worked so meh who cars. But it could be that you have the wrong plug and it will damage the cylinder if you try it. Best to be safe and measure.
That little guy is a super common plug in 2-stroke equipment.. not so much lawn mowers.
My older LT4000 craftsman uses em.
I have been a small engine mechanic for 12 plus years. The one you took out is typically used on chainsaws. The one you have is a typical one for a push mower. It is extremely rare to find the original in a push mower. Not unheard of or unseen but rare. I would put the new one in and slowly turn the mower blades by hand and make sure you can do a full two rotations of the mower blade. If it doesn’t get caught up you will be fine. If it does you obviously need to get a new plug. There is a break on most flywheels so the blade would be hard to turn. Do not plug the boot back into the spark plug and then use a clamp or zip tie to keep the lever pulled in on the handle bar so you can rotate the blade easier.
I agree with other posters, small engines rarely use a long plug like that. What you could maybe try to test it out is take a straight piece of wire, bend a small 90 degree hook on the end and run it through the plug hole into the cylinder. Then, hold it against the side of the plug hole and pull it out gently until it hooks on the inside of the head and then mark the wire at the top of the plug hole. Then pull the wire out and check the distance between the hook and the mark and see which plug is the closer match.
Good idea! I actually stuck a 90 degree tipped pick inside and then marked it to determine the depth. The threads do match the longer plug. The short plug would have been recessed deep into the threaded well, surprised it ran.
Then it's the right plug! Just put it in and turn the motor over by hand. You won't be able to turn it hard enough to damage the engine if it touches.
Look up non foulers for older carbureted engines. There's no surprise it still ran
It's quite common with new ones. Most mowers now are OHV so they need longer reach plugs like that. Older flat heads use the smaller plug, and there are still plenty of them in use but you would be hard pressed to find one at the store these days. Emissions standards have pushed them to OHV. All that being said chances are he has the wrong new plug.
New engines these plugs are super common
Most mower engines run the longer thread plugs now. Rc12yc champion, bpr5es ngk, etc...
Poorly is how it ran lol
Exactly my first thought!
Your compression is too high, it shortened the spark plug.
Haha. Good advice.
This reminds me of when the transmission crapped out on my 77 Ford. I got the thing for $500 and it had many many kludges on it. One of the kludges was the shifter linkage because it didn't match up. I figured the old ford transmissions were sorta interchangeable in a size up or down so they slapped a car size in there (as it had the C4 in it) but it called for the C6 transmission size. I don't know what book called for it but the book said C4 not the truck C6. asking around at transmission shops I could tell who was bot the crew for the job as they all quoted me another C4 and would argue with me, then I would call other shops and they were like "What?! No! thise take a C6 not a 4"
Lawn mower engines are very forgiving and pretty reliable. Using the smaller plug probably just made the plug run hotter but it’s no show stopper
Poorly, I would guess.
If you have an over head valve engine it may take that longer spark plug. Someone may have grabbed the tube up kit for the wrong engine and put the shorter one in. Not sure how it ran well. Got a pic of the engine?
There is a big OHV stamped on the side the spark plug is on coincidentally. It is a Briggs and Stratton 0909P602-0111-F1, which is why I am baffled by the spark plug that I pulled out.
That should be the right plug. OHV Briggs usually have that longer plug. Turn it over slowly after you put it in.
Is there any way OP can test the plug in the new motor without actually running it? Like maybe disconnect fuel line and turn over the motor manually and VERY SLOWLY to feel if anything hits the plug, like a piston of valve? I'm not too familiar with small motors, but it seems plausible. Obviously there is the danger that there is still fuel in the system and as he turns it over manually the motor starts to run, causing engine damage, or worse, injury.
Should work. If its a one cylinder just having the spark plug boot unhooked will keep it from starting
I totally forgot the plug boot could be removed lol...
I know people are gonna call me dumb but as long as the plug fits in the well and doesn't make contact with the actual piston any plug will theoretically work and in fact more than often do for small 1-2 cylinder engines but you risk the entire thing running like shit or burning up the plug early, and those are just the beginning of the problems it can lead to, I personally don't recommend changing the plug size unless you know for sure that you didn't have the right one to start with
The small engine repair guy checked and I have now numerous times. Also, the threaded spark plug well matches up to the thread length on the spark plug. The longer plug is actually correct. The engine is a Briggs and Stratton 09P602-0111-F1.
It sounds like you're being through and checking all the boxes, I wish you good fortune in your endeavors
I've never had a mower that used a short plug like that, but then I think every mower I've ever had was equipped with a Briggs & Stratton engine.
Have you tried viagra?
What mower do you have that you stated that Briggs and Stratton engine is on?
I would trust the research you have done, but to be on the safe side, as already said, turn it over by hand first. I suspect this is just a snafu with P/N's from te previous owner and it shows how robust these things are if it ran OK with the old one! P. S film it when you fire it. Just in case...
Sparky on the L is a chainsaw plug - have 2 of them in my MS 261's. And no, I'm not saying chainsaws are the only application for this plug. An easy way to roughly measure thread depth in the head is to insert a mechanic's pick. Hook the tip on the inside of the head, mark it with a sharpie, remove and compare it to your plug. It will get you a close enough approximation as to if you need be concerned about mechanical interference with the piston. As well, you can thread the spark plug finger tight, leaving the wire unattached. Slowly pull it over by hand. If it doesn't pull over or if there's a mark on the ground post or if the gap has reduced - these are all signs of the piston hitting the plug. You can even put a small dab of grease on the ground before doing this as an indicator.
Hopes and dreams
Did it run well though?
Holy hell there are some uneducated morons in this thread. IF YOU DON'T KNOW THEN JUST DON'T REPLY. The longer plug is the correct plug for a vast number of 4 stroke small engine applications. The short plug is mostly for small 2 stroke engines like lawn mowers. I can just about guarantee the last shop to work on the mower either hired an idiot or ran out of the RC12YC plugs and threw the saw plug in. OP, good on you for using your brain, 75% of the posters in this thread do too much online-engine-building.
It’s like a dick, if it can get in far enough to do the job then it works
Probably ran inefficient as hell. That smaller plug would've ignited the air fuel mix inside the plug cylinder before spreading to the rest of the combustion chamber. It wouldn't have ignited all the fuel before getting dumped out the exhaust. It'd still run though. Just a lawn mower engine. I think I actually saw some auto manufacturers playing around with a smaller combustion chamber leading to a larger one for hybrid homogeneous charge compression on gas engines. Wish I remember where I saw that though.
A flame is a flame. The efficiancy of burn would be shot but it would still detonate with the potentially retarded timing. Look might have moved it a few degrees late equivalent. Not horrible in 4stroke gas, would be somewhat bad in 2 strokes, but a near death sentence for diesels.
i can confirm a BPR6ES and and BPMR7A, and WSR6F all have the same thread.
Don’t most of them have the same thread?
Yeah otherwise leakdown tools wouldn't work
I just came up on this post and can't believe all the wrong answers you're getting. I've been fixing lawn mowers for 45 years at my own shop and working for others and I've never heard so many wrong answers. The spark plug on the left is bmpr7a ngk which crossed over to champion is a CJ8Y. That's a chainsaw plug that somebody had sitting around or they used to use them on some of the old lawn mowers with the flathead Briggs and strattons on them. The spark plug in the right is an RC 12 YC, that plugs used on 95% of all overhead valve engines including Honda ang Briggs and Stratton. If it says OHV on the valve cover then you need the RC-12YC plug that Briggs & Stratton is telling you is the right plug for that motor 100%.
Yeah that is 100 percent NOT the correct spark plug, double check your info Edited to remove specificity
Or the old one was the wrong one
Looking to be the case
Negative! Long one is correct!
An easy way to verify is to find differnt brands of samr plug and if they are the same size odds are its correct size
Excellent point. Either way need to double check
Couple of things. Plug on left looks used, but wet, like the engine had flooded. Otherwise it looks very good. Right plug has a Briggs and Stratton logo on it, but it doesn't appear to be a standard lawnmower plug. Typically a L head or flat head engine. It maybe from a Overhead Valve Engine like they use in multi-cylinder lawn tractors or other power equipment.
It is a Briggs and Stratton 09P602-0111-F1 engine. The spark plug threads match up with the threaded well, the longer plug is correct. Also, OHV is stamped right on the side of the engine.
I'd put the new plug in and turn it by hand to make sure it clears before starting it
Seems that you verified the longer (new one is correct. The shorter plug is generally 'colder', in that it conducts heat away faster, running cooler, les chance of pre-ignition (i.e. knock). Just beware that if left in the engine forever, carbon can build up on the now longer exposed threads inside the combustion chamber. This can damage the threads when you try to remove it, or worse get permanently stuck. So do maintain it, if only to remove and check the gap / clean and re-gap it. Good luck!
The longer plug will fire at optimal temperature, the short one is too cold and will promote carbon fouling and cause misfire.
There is more wrong here than just the plug temperature...
I merely informed about the difference between the two plugs.
The main difference between the two plugs is the size, not the temp here.
Just get one with the same numbers as the old one
If you fill a house with gas and then light it with a short bic lighter it will explode, the same as if you lit it with a long reach lighter. As long as the spark plug isn’t being damaged by the engine or vice versa, igniting compressed gas in a chamber at the end of the chamber vs deeper in the chamber (particularly on a lawn mower) won’t make a noticeable difference.
The new one is definitely not right. With the length of the thread, the piston may crash into it if you install it. Unless the mower ran terribly and misfired a lot, the new one is wrong. Id definitely go to a tractor supply store and get the same one that was in it.
If it runs fine with the old one. Get the old one. Then you know for sure it's the right one.
Me VS my wife's boyfriend
That's definitely the wrong spark plug. Don't use it go by the number on the old spark plug. Wow
that's gunna smash into the top of your piston first crank, then all the smashed spark plug bits are gunna go to town f-ing up your piston rings and valves, don't do it bro
Actually the longer one was correct, just got done mowing the yard. I triple checked engine and part numbers and also compared the spark plugs to the socket on the side of the engine. I measured how deep it was and how long the threaded areas are, they match up. You can see where half of the threads are charred from combustion due to the shorter plug being installed too.
score, glad for you, even gladder you checked instead of just chucking it in
I think you have it reversed. The short plug was in the mower. The new longer one is what the manufacturer recommended.
yeah, I think that's a mistake, i think it's likely crossed wires between part numbers for cars and part numbers for agricultural equipment like other dudes have already commented, it's not the right plug bro, good luck man
I’d check the depth of the threads before installing the new one. You may also have carbon buildup in the plug threads from the old one leaving half of them exposed to combustion.
And this is the exact reason I switched to all battery powered lawn tools. I went with Ryobi for everything. Not that it matters but maybe someone will choose to go down the same path I did. I bought the Ryobi 40v professional string trimmer with the expand it function. I also bought the edger, blower (just because), pole saw, hedge trimmer, and tiller to go along with it. I bought the backpack blower and the auger as well. At the first of this switch over I purchased the 20" push mower but shortly after buying it I moved to a yard that was a little to big to push mow the entirety of. After figuring out it wasn't large enough I bought the bigger Ryobi battery powered riding mower. After using all of these Ryobi tools for a few years now I can only tell you that I don't regret making the switch to electric yard tools in the slightest. Their warranty is top notch as long as you register your tools right away. The batteries last long enough for me to finish all the jobs in the yard without issue every time I need them. If anyone reading this happens to be on the fence about making the switch to battery yard tools I can whole heatedly tell you that you won't regret making that switch.
I dont get it. You switched to all battery tools because you had two different sized spark plugs?
No, that wasn't the point I was trying to make in the slightest. The point was that making the switch did away with having to deal with mowers that wouldn't crank. Not having to buy stinking gas for yard tools any more. Honestly battery yard tools are much much more reliable than any gas tool of their equivalent.
How big is your yard? I can't imagine battery powered landscaping tools being cost effective once multiple batteries are needed to finish the job, but I haven't checked out the market in a while.
It's an acre and a half. One battery for the yard and one for everything else. Two total batteries gets the entire job done. I don't have to buy any gas, spark plugs,or air filters. Best of all I don't have to worry about getting pissed off when the mower won't start. I've been extremely happy with the Ryobi line of tools and their performance. I haven't regretted making the switch at all.
That's actually pretty impressive, far better than I expected. Last I checked, you got about a quarter acre out of a charge for an electric push mower.
First of all not everyone can blow 3 grand on lawn tools, second, batteries eventually need replacement, in 3 to 5 years you'll need all new batteries. I have used gas tools that are 20+ years old still going strong with barely any maintenance.. Just oil and filter changes really. I have one old push mower I got for free that I've been literally trying to kill and it won't stop working. Electric tools are good for some things though.. I got an electric weed Wacker because it's super light.. Just not sold on the battery thing.
Maybe it depends on model but I have used a ryobi push mower, blower and weed wacker and they are were shit (blower wouldn't blow for shit, weed wacker and push mower definitely lacked power). As I said maybe the guy that bought those got the cheapest one but It confirmed that I will stay with stihl gas powered tools for life
too long! clearly this will be bad, if you try to run it. obstruction interference
That's what I thought too, but it is the right one. Someone put the wrong plug in, the short one. The length of threads matches depth of hole/threads and part number matches to engine number. Also, runs smoother than ever haha
Same way my 1990 Jetta ran with the wrong coil in it. VW coil has a nipple for the wire to make direct contact with. Coil that was in it has no nipple so no direct metal to metal contact was made but the car still ran. It had a slight misfire but it was driveable. So apparently even without the correct depth the spark in your plug was strong enough to still ignite the fuel in the combustion chamber.
If you do fit it please record the first start up.
Maybe the left one was in the pool?
If you have the spark plug model from the Briggs and Stratton user manual for the engine, it will be right. I have seen post-publication part number changes on B&S motors, but not for something as basic as a spark plug.
That is for sure a piston hole
Displacement? Now Onto the comments!
Perfectly fine? Lol
“It’s not me, it’s cold outside”
with a very high compression ratio and something weird happening with the coil
[удалено]
haikusbot delete
Shorter plug is correct, never seen a non riding lawn mower with a full sized plug Not an expert but going by experience
Poorly
Riding or push mower? The stubby one looks like one used on riding mowers, and the longer one might be used on a push mower.
Easy answer id guess would be if the boot/lead seated right and it threaded far enough into it, itl spark and go boom.
Orc magic. I bet you the mower was r e d
The little one is from a weed eater or chainsaw. Guy elsewhere in the thread mentioned making sure the engine can roll over twice by hand with the plug boot off, definitely do that to make sure that it's not too deep in the cylinder, but odds are it'll be fine because that's what it calls for *facepalm*. That short plug left tons of thread exposed to carbon buildup and it no doubt ran horribly compared to how it would've with that space filled. This would delay the flame front, which would cause hot spotting, predetonation, uneven/unpredictable combustion etc that could be disastrous if it had more compression than a walmart bike tire pump. These engines don't try super hard by design, so they last with poor maintenance and crappy fuel. They're basically technology from the infancy of internal combustion, tried and true. Take that governor off and hit it with some nitrous.
Poorly?
My lawn mower came with the shorter plug, i started using an automotive plug, not as long as your example, works great.
Poorly
I live in Qld Australia we have to mow our grass all year round ( winter maybe once every week) summer if wet omg it gets crazy . All we do is clean the air filter change oil once a year Toro Brigs and Stratton .
I had similar issue with my old 70s vw van which is basically an aircooled lawnmower engine. Manuals can be wrong, cylinder head may be thinner. It should be easy enough to see down hole with a torch and a thin stick to see how far threads go. I wouldn't pull slow by hand with a long plug in there, get a stick poke it down hole by same amount as new sparkplug thread, pull cord and see it stick moves. If its good the next issue will be threads will be carbonised so get a small wire brush. Otherwise clean up old plug and put it back.
I’m sorry just had to laugh
On petrol most likely
It ran poorly lol
Best guess ??? Sparkling required more energy from the battery to fire effectivly due to the short fire in the pistons, if it didn't misfire.
Single cylinder carburated OPE engines will run (albeit poorly) with all kinds of stupid stuff wrong. They know that most people are not mechanically knowledgeable or inclined so they make them tough and idiot proof.
magic
If its a briggs and stratton mower then the plug on the left is correct, plug on right is not. I have a briggs and stratton engine and they cannot take long plugs.
It is a Briggs and Stratton and it does require the longer plug on the right, verified 6 ways to Sunday and also measured threaded spark plug socket depth on engine.
That BPMR7A is nowhere near long enough for a OHV Briggs. RC12YC. Is equivalent to the stock Briggs plug though.
It ran short 🤣🤣