Question about 1980 Yamaha XS 400 Special

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I had a hard time starting the 1980 xs 400, one piston is not firing, just dumping out gas smoke into the muffler. Muffler is cold on that one side.

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It sounds like you have a carburetor float that is stuck in the down position flooding the cylinder with gas. Start by removing the carburetors and giving them a thorough cleaning . Closely inspect the sides and tips of the float needles.If they show wear or damage replace them. If you have black plastic floats , test that they float in a cup of gas and do not sink . If the float sinks replace it. Ethanol fuel will saturate black plastic floats over time causing them to sink. Change your plug , it is probably wet fouled from the gas and check the new plug for spark. Also check that your crankcase has not filled with gas during the flooding. That is why you should always turn your gas off when not riding so if a float sticks you do not ruin your oil. If gas has fouled your oil, change your oil.

Posted on Sep 12, 2010


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