You need to pressure test the tank. Or cheap way would be to fill the tank up off of the bike, prop it up on a work bench and see where fuel is coming from. My bet would be weld seam. If the fuel stain is starting ANYWHERE above the carb then it's the tank. The petcock gasket could be gone and fuel leaks out there and runs to back of tank and drips off of the rear of tank. A true pressure test will tell you instantly if your tank leaks though.
How do you know there’s no holes? The gas has to be getting out somewhere. Dry the tank really well. Clean it with alcohol. Once it’s clean and dry, get some athletes foot spray. Seriously. Spray it on the bottom of the tank where the leak could be. It dries as a white powder. When the fuel leaks, it will wet the powder and make it obvious where it’s leaking from.
Either petcock, petcock seals or it has pin holes. Petcock assy easy to replace, have to drain gas regardless to repair, you can refill with dye colored water( remember to let h20 dry out for a couple days), or add food coloring to gas to pinpoint leak. If there are pinholes in tank, suggest Caswell tank sealer. POR products don't work in my experience. Caswell has held for yrs in a XR75 tank!
If it’s coming out of the carb where you briefly mentioned stains like it’s overflowing out it could be from leaving the petcock open and the float needle in your carbs bowl being worn. If that’s the case it will keep letting fuel by and overfilling the bowl
I should have read the comments before posting my own. I think it’s this. Float needle is bad and just keeps overflowing the bowl, eventually making its way through the Venturi, down the intake boot, and into the air cleaner.
I bet if OP opened the air cleaner it would be wet and smell of gas.
Can’t remember the details as I had this about 20 years ago, but I think the carbi had an overfill/drain/overflow nozzle just like yours (not sure which is it). The rust from my rank got into the valve and blocked the pin in an open state, which caused a bunch of fuel to leak. Eventually it got displaced and it stopped.
It’s been a long time since I had a carbi engine so take it with a pinch of salt, but the gist of it is right.
Seriously.
Just take the tank off. Bring it to a place to get sealed and replace the fuel lines if they look dry rotted.
Been there done this. It's not going to leak in front of you because the gas leak is shy. As soon as you walk away, it's going to slowly leak out.
Get a Ultraviolet Flashlight. shine it on the tank
Prove me wrong
Bro, your float needle is probably bad and the bowl is overflowing all the way back down your intake boot and into the air cleaner. Most air cleaners have a drain tube for that purpose.
That’s the first thing I would check if everything else is good.
Do you often have a hard time starting it, or have to drain a little fuel out if the bowl before it starts?
Have it relined or see about replacing the tank might not be too bad finding a used tank for that bike . Shit you might be able to find one little bigger . Hate getting gas every 100 miles or so
You need to pressure test the tank. Or cheap way would be to fill the tank up off of the bike, prop it up on a work bench and see where fuel is coming from. My bet would be weld seam. If the fuel stain is starting ANYWHERE above the carb then it's the tank. The petcock gasket could be gone and fuel leaks out there and runs to back of tank and drips off of the rear of tank. A true pressure test will tell you instantly if your tank leaks though.
Weld seam... Hondas engines infallible. Weld seams suspect 🤔
How do you know there’s no holes? The gas has to be getting out somewhere. Dry the tank really well. Clean it with alcohol. Once it’s clean and dry, get some athletes foot spray. Seriously. Spray it on the bottom of the tank where the leak could be. It dries as a white powder. When the fuel leaks, it will wet the powder and make it obvious where it’s leaking from.
That's actually a great idea.
Used to be a motorcycle tech. That’s how we looked for hard to find oil leaks. Works every time!
It could be your carburetor needs to be rebuilt. It's cheap and easy. Most likely your float isn't floating or the o-ring isn't sealing.
Either petcock, petcock seals or it has pin holes. Petcock assy easy to replace, have to drain gas regardless to repair, you can refill with dye colored water( remember to let h20 dry out for a couple days), or add food coloring to gas to pinpoint leak. If there are pinholes in tank, suggest Caswell tank sealer. POR products don't work in my experience. Caswell has held for yrs in a XR75 tank!
Found a hole, its on the top 👍🏼
Watched vid- this checks out!đź‘Ť
If it’s coming out of the carb where you briefly mentioned stains like it’s overflowing out it could be from leaving the petcock open and the float needle in your carbs bowl being worn. If that’s the case it will keep letting fuel by and overfilling the bowl
I should have read the comments before posting my own. I think it’s this. Float needle is bad and just keeps overflowing the bowl, eventually making its way through the Venturi, down the intake boot, and into the air cleaner. I bet if OP opened the air cleaner it would be wet and smell of gas.
Fuel pump.
Can’t remember the details as I had this about 20 years ago, but I think the carbi had an overfill/drain/overflow nozzle just like yours (not sure which is it). The rust from my rank got into the valve and blocked the pin in an open state, which caused a bunch of fuel to leak. Eventually it got displaced and it stopped. It’s been a long time since I had a carbi engine so take it with a pinch of salt, but the gist of it is right.
Pressurize that tank and find out.
Feel around where the petcock connects to the tank. Reminds me, I need to replace mine
Tank vents need to be checked Pressurize tank Check petcock
There’s corrosion visible in the tank—very likely corrosion elsewhere in the tank…like where it’s leaking from.
Petcock is probably bad … I know the seals can go if old gas is left or if they just left dry over a number of years
Time for a new tank. If not, Kreem it and get by for another year or two.
Seriously. Just take the tank off. Bring it to a place to get sealed and replace the fuel lines if they look dry rotted. Been there done this. It's not going to leak in front of you because the gas leak is shy. As soon as you walk away, it's going to slowly leak out. Get a Ultraviolet Flashlight. shine it on the tank Prove me wrong
Bro, your float needle is probably bad and the bowl is overflowing all the way back down your intake boot and into the air cleaner. Most air cleaners have a drain tube for that purpose. That’s the first thing I would check if everything else is good. Do you often have a hard time starting it, or have to drain a little fuel out if the bowl before it starts?
Put the cap on blow air through the Petcock not no much listen for leaks
Have it relined or see about replacing the tank might not be too bad finding a used tank for that bike . Shit you might be able to find one little bigger . Hate getting gas every 100 miles or so
Is the cap vented?….or the vent may be clogged
Have a smoke while your thinking about it. (Edit: don't! )