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Old 01-12-2009, 01:50 PM
Bikeguy Joe Bikeguy Joe is offline
Godfather of Motorized Bicycles
Join Date: Jan 2008
Location: up north now
Posts: 11,531
Default Thought and Observations- Air leaks

Here's a couple of thoughts about the common and dreaded air leak.

This is not all of the possible causes, but two that may be over looked right off the bat when assembling the bicycle motor kit. Both are easily detectable, and easily fix before they cause you any problems.

Look closely at photo 1. You will see two things.
1. The "flat spot" where the carb top threads onto the carb.
2. Those slots...some go deeper than others. The face of the carb hits the end of the manifiold, and the slots leave little holes where air is sucked in.

(For no. 1.) Use a little RTV in the carb top and let it dry before screwing on the carb, or make a gasket to put in the top so when you screw it down, it will seal. I have seen them with little or no flat spot, if you get a carb like that, consider yourself lucky and blessed!

(For no. 2.) I have used a belt sander and/or a file to grind down the face enough so when the carb is mounted, it will seal against the manifold. Some people use an "O" ring in there...I prefer the grinding/filing method.

For either, use a little RTV or Rector Seal (removeable sealant used on gas pipe fittings) to goober up the top of the carb, or the manifold to carb area.

Let it dry before use.

Thanks for listening,
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Last edited by Bikeguy Joe; 01-12-2009 at 01:53 PM.