Ok, heres what happened to my 400ex. I bought it used. Shortly after that, the top end got way to hot from not enough oil. So, I took it in, had it bored to clean up the bore, Wiseco piston instelled. Ran fine until too much dust messed up the bore. Now Im going in for another bore. If when it got too hot the first time, is it possible that the cylinder head was in any way fatigued so that no matter how many times the bore is cleandd up it will still have a short life for each additional bore. Its only been bored once. and it was a minimal bore to clean it up?

 

get a new top end

 

Im having the piston kit done. But I wonder if the cylinder needs to be replaced due to excessive heat.

 

i hope you're washing out that cylinder with warm soapy water before you install it....

 

What does bored to clean up the bore mean? Do you mean it was simply honed or do you mean it was taken to the next over size?

If you are letting dust get into the engine you will have to over-bore and/or resleeve constantly. Are you running with no air cleaner at all?