Posted by David K on July 30, 2003 at 06:59:12:
In Reply to: running rich? posted by Johnh on July 30, 2003 at 06:33:46:
Yes, there is a very likely cause for this all of a sudden richness. It happened to me on my Yamaha Virago. What happened is the diaphragm in the petcock ruptured and allowed the vacuum hose to suck gasoline into the carburetor manifold.
To check out the possibility of this being your problem---remove the vacuum hose to the petcock and insert a blockage up the hose, (a plug) than replace the hose to the petcock. The engine will not run now in the ON position, so you will have to run the engine in the PRIME position of the petcock. Take the cycle for a long ride and have someone follow you, to watch for black smoke (also check the gas mileage).
If you have already fowled the spark plug, then put a clean plug in he engine, before doing this test.
If I am right and this is the problem, you will have to order a K & L petcock repair kit, for $25. The petcock can be taken apart for repair, without taking it off of the gas tank.
The repair kit will have the diaphragm and two "O" rings at least. It might also include a tank gasket, screws and a small coil spring, but the only thing that you will really need is the diaphragm. Unfortunately the dealer will not sell a diaphragm to you, so you need him to order this aftermarket repair kit from K & L!