Air leak

[Josh_wilcoxx]

Hey guys, it's me, back with another problem. JUST put a brand new china engine on, and it's acting like it has a air leak (engine revs high when clutch pulled in). What would be the easiest way to locate the leak before I replace every single gasket? Also, if it's worth anything, I have a high compression head and a HP carb from eBay.

 

[zean]

I would spray dish washing liquid dissolved in water around the: head and base gaskets, intake/ jug gasket, intake-carburetor junction and the crank seal behind the magneto.

 

[zean]

Excuse me, I meant to say that I would check close the crank seal behind the magneto, not spray soapy water in and around the magneto.

 

[Chainlube]

The carb itself needs a different throttle cable, if you used the OE cable it could be a little short.

If you want advice on that carb, don't ask me, I've never had one to run right.

 

[Karl Snarl]

I fire it up and use a propane torch ( not lit, just gas coming out). When it revs, you found a leak.

 

[Heavyload]

Here is something i noticed on my build. Intake and exaust ports on my 80cc were pretty rough. Both flanges not smooth, corrected with a flat file. Both ports between flange and piston were really ugly, pitted not perfectly smooth. Cleaned and polished for more efficient air flow in and out of the cylinder. That my 2 cents worth.

 

[Freddy Snottgrass]

If you don't have a propane torch, you can use carb cleaner. When you spary it near where the leak is, it will bog down. Be sure and spray your magneto cover as that will tell you if your crank seal on the magneto side is off.

 

[Karl Snarl]

If you don't have a propane torch, you can use carb cleaner. When you spary it near where the leak is, it will bog down. Be sure and spray your magneto cover as that will tell you if your crank seal on the magneto side is off.

Problem with carb cleaner is it eats stickers, paint, seals. I won't even use carb cleaner to clean the carbs on my motorcycles. It swells all the seals and dry's them out. A can of keyboard cleaner works the same, but won't damage anything.

 

[Axl Myk]

Just use a butane lighter. Unlit, of course.

 

[Chainlube]

Here is something i noticed on my build. Intake and exaust ports on my 80cc were pretty rough. Both flanges not smooth, corrected with a flat file. Both ports between flange and piston were really ugly, pitted not perfectly smooth. Cleaned and polished for more efficient air flow in and out of the cylinder. That my 2 cents worth.

For best performance, polish the exhaust port only. Leave the intake a little rough to create a little turbulence so the fuel doesn't settle out of the mix.