Good Friends,
I just picked up an 80's YFM80 Moto 4 Yamaha quad at a garage sale. The owners had it all apart in two different crates. I have a Clymer manual that covers the 80cc Moto4 from 85 through the 2001 badger.
This manual states that there is a fill and drain plug for the final drive fluid as well as drain and fill plugs or the engine oil....Maybe I am blind..??..but I can only find the plugs for the engine oil.
Is it possible that on these early models that the final drive and the engine shared the same fluid..?..Or is there some prehistoric way to change the rear final drive gear oil that I cannot figure out..?
Please help me out with any information...You can email me at PCYR2@***.net
Thanks
[img]i/expressions/face-icon-small-confused.gif[/img]

 

i had an '88 yamaha moto 4 80. It was shaft drive, just as i'm sure your's is. there was DEFINITELY NO access to fill or change the diff fluid. it was sealed. i never took it apart to see, but there was definitely no way to add or change that fluid. I actually thought it might be sealed with grease like our PW 50 was (dirt bike). i still have an older manual for it aswell.... could be a Clymer....not sure. it covers both this unit and the YFM200 (which we still have). the 200 has a drain plug, etc...., but not the 80.

 

Confused is wright. The rear is filled with grease. This style was known to fail. The seals could get torn up and the grease would leak out, or after time, the grease breaks down and doesn't lubericate the way its supposed to. I've seen guys drill a hole in the case and tap it for a regular plug. All the newer ones have the drain and a dipstick/ fill plug.

 

i only sold ours a year ago, and it was still perfect. we went thru lotsa water too. not to say asfasasu isn't right, just don't write it off before you try it.

 

I wouldn't give up on it either. Most of the ones that failed were because the owner never noticed the grease leaking out or just didn't care. No shaft drives work when all the oil is gone. (not for very long anyways) Most give you a hint before bitting the dust. They will start making noise. If your worried about it, you can split the gearcase and clean it up. Then fill it back up with grease, or as I mentioned earlier, drill a hole for a plug then use some good oil. The rear end in these is probably the weakest link, but if you take care of it, it should last a very long time.