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I have a 2002 Yamaha Big Bear 400. Thas bike runs great and has good power but it recently started smoking White/Blue Smoke.

I have done a compression test and the reading is between 110 and 120 PSI, I have changed the oil and also drained and changed the Gasoline.

We went riding late last year and my son-inlaw was riding this bike and he got stuck in a Mud / Water hole that sunk the bike up to the seat, it remained running for a while and he attempted to get it out but it eventually quit. We towed it back to the trailer and after drying out and changing the plug it fired right up, it ran rough for a while but that straighted out.

Now it started the smoking, I have read in forums that one of the vent line could be clogged but I have checked all the rubber lines and they seem to be clear. But they keep talking about a crankcase vent being pluged causing pressure to build and force oil into the cylinder.I can't find a vent hose on this bike but the hoses around the air box are clear. I have purchased the Clymer repair manual, It tells me how to fix the problem but dosen't tell me how to find the problem. Should I be looking at a valve problem?

Help.
 

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I'm having the same problem with the same bike.2002 yamaha big bear 400 4x4.still runs good but suddenly started smoking and blowing oil out the exaust.If I find a cure I'll post it here for you.:dunno:
 

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The vent you are looking for is on the right hand side of the crankcase, black tube about half inch in diameter. What kind of oil are you using, because my bike started smoking and I switched to yamalube and it stopped. Hope this helps.
 

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I'm having the same problem with the same bike.2002 yamaha big bear 400 4x4.still runs good but suddenly started smoking and blowing oil out the exaust.If I find a cure I'll post it here for you.:dunno:
Hmmm, water could be in the engine which mixed to the engine oil. Thats usually the case for cars, not to sure about atvs though
 
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