power valve holder breaking

[zuki dave]

2003 yamaha yz 250 main power valve stop broke at little tabs that hold valve. did not know at time bike lost power. started cking. found piece in sub. port. installed new thinking freak problem. ran about 10/15 hours didn,t even no disassembled to freshen top end for new season found new stopper both ears broken. showed local shop no answers. any body else + possible fix. was having some detonation last race . also bike does detonate easy on preium fuel must run 1/2 race 1/2 pump fuel.

 

[Mainjet]

Power Valve

Install new part numbers from 2004 YZ 250, no ideas on detonation. Perhaps check for correct ignition timing.

 

[zuki dave]

thanks for info. will ck on difference you have seen this problem ck,d ing. timming was perfect. also was told they run good with 2 more degrees timming. once all this snow is gone will mix stronger race /pump gas mix. was working on bike last night founr crack down side of piston now.