she needs a rear end for a yamaha moto4 100cc or 80cc 1987.

this is the second set of gears on this thing .I am going to replace the grease with 80/90 gear oil this time maybe it will last longer. What would make the gears tear up like that?

 

First off welcome to the forms!!! and as for the gears id think either watter is getting in it or lack of lube.

 

Some of the older moto's had gear problems. Don't know why but some just didn't last to long. I believe the rear ends are the same as the newer ones EXCEPT the newer ones have a drain plug and a dipstick and use gear oil. They seem to last longer if you keep good oil in it at the proper level. The grease seemed to break down and not lube the gears very well.