1990 Big bear 350 4x4 Oil seal

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Oct 30, 2023 | 08:11 PM

derikthehunter

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1990 Big bear 350 4x4 Oil seal

I am having a problem with excess oil getting into my middle gear drive. 1990 Yamaha big bear 350 4x4. When I remove the fill cap to the middle gear box, oil just starts poring out. When I change the oil, I put the right amount in the middle gear drive the manual calls for, and it is fine. I run the atv for a minute then shut it off and let it sit for a couple of minutes. Then When I open the fill cap, oil starts gushing out. l I am assuming there is a seal or O-ring that is worn between the crankcase and the middle gear drive that is letting more oil overfill it. I have looked up part diagrams and a couple videos (not many videos out there on this machine), but not seeing anywhere how it could overfill from crankcase to middle gear drive. Any ideas where this seal is or how to get to it? Thanks

Oct 31, 2023 | 04:21 AM

merryman

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From: Lancaster England

If it is not peeing oil from the seals for front and rear propshafts, I wouldn't worry about it. If it is the model I think it is, removing that angle drive is a pig of a job, and I seem to recall, most that I used to service, had the drive gear full and overflowing. I can't see any seals between gearbox and angle drive on parts drawings anyway.

Oct 31, 2023 | 01:35 PM

derikthehunter

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Quote:

Originally Posted by merryman

Ok thanks for the reply. It is leaking a bit out the top rear, at least the ujoint and stuff has a film of oil on it. But It is not coming out to the point I am loosing oil in the middle gear drive after riding for hours or anything. I just didn't want to have it so full that I would risk blowing out the good seals or something