my son's250x leaks oil at the countershaft seal. i replaced it twice and it leaks bad within a few hours. any ideas what would cause a seal fail so quickly?

 

check the countershaft to see if it is warped at the surface where the seal touches it

 

It could be like chevy v8 timing cover oil seals,used to get leaks from the seal wearing the diameter down over the years.There is a sleeve kit to put the worn spot up to the correct diameter,and make it seal again,so maybe there is a sleeve kit to help out your quad's countershaft? maybe if you measure the shaft,you can get something to fit from an auto parts store,if the local quad dealer doesn't have anything to fit. Hope that is some help.

 

Sounds like a bad bearing on the countershaft to me. When you had the seal out the last time, did you notice if the shaft had any movement??

Also, running a chain tighter than it should be will cause the seal to wear. I'm not talking "guitar string" tight, but it doesn't take much. Especially since the chain tightens with suspension movement.

 

i found slight end play but no play up and down. the new seal did not last 2 hours. the chain has about an 1 1/4 of play.