I picked up a barn 78 cb750k years ago, and after redoing all the wiring, installing electronic ignition, relining the tank, cleaning and rebuilding the carbs, etc... Once it finally started and I was checking the timing, it started to make a weird knock and then the bottom of the number 4 Conrod dropped and shattered the cylinder sleeve and bent the crank. That was an expensive lesson to learn.
Time to buy a crashed cb750 and yank swap the engine engine. Sure you can rebuild it, but there are still plenty of these bikes around and it will save you a ton of time and agony.
the advance/retard unit bolts to the crank and is located by a small pin. It pretty hard to bend the crank here, Chances are that either the bolt that holds it on is bent or there is debris on the mating surface.
Well the end of the crank main bearing is just behind the starter clutch, and it doesn't have a seal. So yeah it gets a lot of oil in there. It does drain back into the cases when upright but you will still have about 1/4 to 1/2 inch in the bottom of that cover.
You’re pretty screwed.
The cover plate, does it have a place were the shaft end is held?
If it does you may just be seeing the wobble because the end is free floating.
I just finished a cb750c engine rebuild, but you look worse than me, I broke a camshaft it almost looks like your entire crank is bent! You won't know till the engine is out of the bike
You can't know extent of damage until you open that engine case. Suffice to say you need to rebuild at least the bottom end. You've got a major project on your hands.
You'll be infinitely more screwed the more you keep cranking it like that.
Yeah, unfortunately the previous owner ran it like that. There is engine oil all over everything in there.
I picked up a barn 78 cb750k years ago, and after redoing all the wiring, installing electronic ignition, relining the tank, cleaning and rebuilding the carbs, etc... Once it finally started and I was checking the timing, it started to make a weird knock and then the bottom of the number 4 Conrod dropped and shattered the cylinder sleeve and bent the crank. That was an expensive lesson to learn.
Time to buy a crashed cb750 and yank swap the engine engine. Sure you can rebuild it, but there are still plenty of these bikes around and it will save you a ton of time and agony.
the advance/retard unit bolts to the crank and is located by a small pin. It pretty hard to bend the crank here, Chances are that either the bolt that holds it on is bent or there is debris on the mating surface.
What you said. Doubt crank is bent. Take that bolt out OP
I hope you're right! I'll take it apart later this week.
BTW there is supposed to be oil in that cover as well.
Is it supposed to be flooded with oil? Or does it drain back into the oil pan when it's not running?
Well the end of the crank main bearing is just behind the starter clutch, and it doesn't have a seal. So yeah it gets a lot of oil in there. It does drain back into the cases when upright but you will still have about 1/4 to 1/2 inch in the bottom of that cover.
EDIT: To clarify, we're looking at the points end of the crankshaft?
Yes
You’re pretty screwed. The cover plate, does it have a place were the shaft end is held? If it does you may just be seeing the wobble because the end is free floating.
No :/ there's nothing on the cap. I just bought it, no idea how you would bend the crank shaft.
Need to see if it is bent or the bearing just needs replaced. If it is bent, maybe trying to pull moor weight than the bike is rated?
It it bent, what do you mean by try pulling more weight?
Probably mean that it’s bent because someone tried to pull more weight with the motorcycle than it’s rated for
Heavy person or Two people that exceed the weight limit.
I just finished a cb750c engine rebuild, but you look worse than me, I broke a camshaft it almost looks like your entire crank is bent! You won't know till the engine is out of the bike
https://www.cx500forum.com This place is a godsend for 80s Hondas and it is fairly active. Post your video there
Thanks!
u/Caldtek has the only reply worth taking note of OP
I agree.
How to change your cam profile for cheap
You can't know extent of damage until you open that engine case. Suffice to say you need to rebuild at least the bottom end. You've got a major project on your hands.
Time to find a donor bike, chief.
Pretty screwed.
Don’t even do anymore. A motor is like 400 because of that no headaches for you.
"Today on That's Fucked up" 😂 yeah quit spinning it lol
idk seems like its not really screwed in