Do i need top end rebuild??
 

Hello everyone,

My stepson and his dad just picked up a 2016 kx250f. It ran fine for a few hours then wont kickstart. Confirmed spark, and bike has fuel. Even tried pulling plug and dropping a little fuel in, still no start. I confirmed kill button was operating properly not sure if that matters. Decided to check valve clearance. Had .35 on both exhaust valves and 0 on intake side. Pulled bike had 2.9 shims in exhaust , one intake had a 1.75 other had a 1.3. Knowing i cant get correct shim without some gap I pulled shims on intake side and reinstalled everything. Couple turns of crank, lined back up tdc, exhaust measured same which it should cause I left shims in intake was still at 0. I tried rotating engine while seeing if I could valve cap to wiggle or move at all and at no part of rotation would it have any gap movement.

So I assume guy shimmed it to run knowing it would have a few hours and be done. What do you guys think???

Verify your compression test as well. You are on the correct trail. Compression is key to these machines. Proper rings and valve adjustment for operation and starting.