Engine Puttering?

[psprat496]

This is weird. I finally put another bike together with the new style NT carb. The engine is a Skyfire 66cc with about 50+ miles on it. The bike runs pretty well but for some reason when I rev the engine it will start puttering. It revs up but then it takes at least 2 seconds for it to rev back down to its normal idle.

Any ideas what could be causing this?

 

[gavmiester]

sounds like an air leak making it run to lean try it with the choke half on if it improves its running to lean,then run it and spray wd40 etc around carb / manifold area helps locate source of leak.

 

[psprat496]

Probably four cycling, possibly air leaks. Squirt some carb cleaner around the intake, at the carb and at the cylinder, with the engine running. If the RPMs change, you have an air leak.

Might be worth dropping the float bowl and making sure the jet and emulsion tube are in tight. Otherwise, run it for a while and don't worry about it until you've got a few tanks through it.

Would an air leak damage the engine if ignored? And if I do find the leak what should I do to repair it?

 

[Maxvision]

I had the same problem when I drilled my carburator jet too big. Even though I let go of the throttle gas would still suck past the needle. Did you try dropping the needle a notch or two?