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higdon87

2001 400ex smoking like a freight train

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Need some help i have a 2001 400ex that smokes on start up and smokes even more when you give it throttle. I just noticed that it leaks oil at the header and motor connect. I just got it from a guy that said he rebuilt the top half and he told me that the valves needed to be adjusted. But what will make it leak? Thanks in advance

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What will make it leak? Well unfortunately, possibly a poorly done rebuilt upper half! Oil is getting into the combustion chambers which causes the smoke. Could be the head gasket was not installed properly, or the head deck had some debris between the gasket and the head or block. Also could be the piston rings were not aligned properly allowing oil to get by. Also check for the presence of, and the proper installation of the valve seals. Oil can get by those too and drain into the combustion chambers.

Probably not what you wanted to hear, but smoke is caused from oil in the combustion chamber. These are three ways it could get there.

Also, this is probably a dumb question, but I assume you are not putting oil in the gas like you would for a 2 stroke engine.

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