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Old 04-21-2009, 09:16 PM
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Earthman Earthman is offline
Motorized Bicycle Senior Member
Join Date: Mar 2009
Location: Pittsburgh, PA
Posts: 82
Default Which way to move stop on needle valve to lean out mixture?

Iím using an engine kit from Bike Berry in which the motor and exhaust are painted with black powder-coat paint. The paint on the exhaust is flaking off in large chunks, exposing the steel beneath. Iíve only run the engine for about an hour. Is anyone else having this problem?

I wonder if my mixture is too rich and the unburned fuel is being consumed by the catalytic converter, which is making the muffler hot and burning off the paint. I think this may be a possibility because I checked the temperature of the motor, exhaust pipe, and muffler using an infrared thermometer. The temperatures were <200 deg F, <200 deg F, and >400 deg F respectively. I canít measure anything greater than 400 deg F.

I guess the paint could be peeling because of poor workmanship too. In any case, if I wanted to lean out the mixture, which way do I move the stop on the needle valve in the carb - toward the top or bottom?

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