I fianlly got my new piston and put my 400 sport back together.
The problem was i was burning the top of the piston.

From other postings the conclusion was that I was running lean.
I cleaned the carb, reset the needle to run richer.

Is there any other reason for this quad running lean.
Where should I look?

Thanks for you help
tutiii

 

LEAKING CRANK SEAL

 

can you tell me where that is?

thanks
tutiii

 

also go up one size on your main jet to be safe and if it runs to rich then switch back

 

The needle change will richen it up very little. Like tbsleeper said, go with a bigger main jet.

 

If the crank seal was bad won't i leak fluid from it?

 

dont worry about that that guys been saying that to everyones questions

however it could cause you to run extremely lean....

 

the first time the piston burnt, there was nothing changed. this quad has run perfectly fine for years. just added gas and it went. i never changed anything.
so i'm thinking something had to give way. the question is what?