bad engine vibration

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pedrorican43

New Member
May 8, 2014
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williston
Hello to all. I am just finished my bike build last wee, road it a few times with no issues.....until this past friday. I was on my way home, and noticed that when I pulled my clutch lever in as I was comming to a stop, my engine revved real high, and my bike vibrated badly. Any idea why this happened?:-||
 
Chaz

Chaz

Well-Known Member
Jun 3, 2012
1,004
72
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Vancouver, British Columbia
Assuming you have the basic chinese two stroke kit. The normal vibrations of these engines is enough to throw off your carb and throttle adjustments. Check that your carb is mounted properly, your throttle cable is operating smoothly, and check your idle settings both mix and the top of the carb cable adjustment.
 
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
Chaz is correct and I'll add that your symptoms are consistent with an air (vacuum) leak in the intake circuit. Somewhere downstream of the carburetor. The two most common areas are the carb where it attaches to the intake manifold and the gasket sealing surface of the manifold where it attaches to the cylinder. Leaks at either area will allow excess air to enter and provide a lean air to fuel mix resulting in a fast idle speed and poor performance.

This, as Chaz mentioned, is assuming you have a Chinese 2 stroke engine. It is important that you tell us what engine you have when asking for help or advice.

Just curious but is your location, 'Williston', in Florida?

Tom
 
Last edited:
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skitchfish

Member
Oct 27, 2010
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Michigan
Pedro, Seeing how you just put every thing together and have a few miles on her you should inspect all nuts, bolts and screws for appropriate snugness. You should do this most every time you ride, and definitely on a new build.

Just a guess but sounds like loose intake or carb clamp. Tighten everything and have fun.

If it wont stay tight, blue loctite and Sealsall will become your friends.
 
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
No problem, Skitfish. You simply reinforced what has already been suggested.

To the OP I'll also ask if your engine is mounted solid to the bike frame? If you're trying to use any rubber or resilient material between the engine and frame, that too can cause bad vibration problems. Don't rubber mount the engine. Mount it solid.

Tom
 
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