1986 Yamaha Moto 4 YFM200DX Diff Oil

[Steve Bethany Poston]

I just got an old YFM200DX Moto 4 and upon checking the oil in the rear differential I took out I assume the fill plug and it fished out old nasty oil. I plan on flushing the oil and replacing but was wanting to make sure if you drain bottom plug and just fill up to the check plug. Only thing I can think of someone filled it up by the breather on top? Plan on unhooking the hose and blowing it out tomorrow. I also do not have a service manual yet. Also right now the diff vent hose just goes up under the tank to nothing. Does it plug into back hole in the air box? Thanks 

[Ron Jones]

On 5/10/2020 at 1:18 AM, Steve Bethany Poston said:

I just got an old YFM200DX Moto 4 and upon checking the oil in the rear differential I took out I assume the fill plug and it fished out old nasty oil. I plan on flushing the oil and replacing but was wanting to make sure if you drain bottom plug and just fill up to the check plug. Only thing I can think of someone filled it up by the breather on top? Plan on unhooking the hose and blowing it out tomorrow. I also do not have a service manual yet. Also right now the diff vent hose just goes up under the tank to nothing. Does it plug into back hole in the air box? Thanks 

That’s where my breather hoses go on my 2000 grizzly. Look for witness marks where it is now. If it passes under a little bar and the rubber is really kinked there like it’s been there for a while good chance that it is in its spot. 

[MSUGeoman]

What oil are you guys using in the rear diff? About to do a full service on our 88 YFM200DXU and planned to go get the oil/supplies this weekend.

[kenikas]

I usually use Mobil Delvac 75w-90 synthetic in mine, our temperatures here can be 110 F in summer, and down to -10 F in winter. and it seems to work well in all our drive gearboxes. It doesn't hurt that I often get it free from work when it goes past the shelf life for use in our aircraft gear drives!