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Discussion Starter · #1 ·
Hey everybody I'm new here, I just bought a 02 400ex. I think this is my 3rd 400? But I bought it last night for $1600 in good shape. I test rose it for a little while the day before and ran great and no smoke. I picked it up yesterday and it just started pouring white smoke when I got home to ride. I did a compression test and it was fine so that made me believe its not rings. I rode it for about 45 minutes and it still smoked bad so I don't think it's valve seals. I texted te guy this morning and I asked him about it and he said he doesn't know he just changed the oil and maybe over filled it. But being the 400ex is a dry sump motor (only pulls from the tank what it needs) I don't believe it could be that unless he filled it to the top with oil. I'm at work now so I can't check until I get home. But does anybody else have a comment on what it could be. Would over filling it do that? I just don't see the valve seals going that bad that fast.

Thanks,
Will
 

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Overfilling with oil it is a possibility - let the motor idle for about 3 minutes, then shut it off and check the oil level. Another possibility is raw fuel in the exhaust. If the petcock is not shut off and fuel overflows the carb, it can cause fuel to pool in the cylinder or the exhaust. Combustion gas will evaporate the liquid and cause a heavy white smoke that seems to dissipate quickly. Oil smoke usually hangs in the air and drifts. If it is fuel in the exhaust, it will quit smoking after running it for a short distance. Shut the petcock off each time you park it.
 

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Discussion Starter · #3 ·
Ya that use to happen on all my 2smokes. But I'm pretty sure it's the oil rings. I've seen it happen where the piston rings are good, but the oil rings are worn or the gaps are aligned. So ill probably just replace the piston and rings while I'm in. Guess I should do valve seals too while I'm in there.
 
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