[tomk_22]

i have a 91 formula plus 521cc , oversized .020 it keeps melting the top tof the piston what is the problem? how do i set the timing and what are the proper jets to use.

 

[finn]

Check for air leaks.....pluged jets....sounds lean

 

[dano]

I agree, sounds like your jetting is way off. To lean, less air, more fuel.

 

[Garganos]

I agree about the jetting. I would also pressure test your engine and check for any seal leaks. To set you timing you need to rotate your stator under the flywheel. You also new a Strobotic Timing Light. A Std. timing light wont work because it won't keep up with the freqeuncy of a 2 stroke. What kind of pistons. If there not Rotax ie Wiesco (seizeco) then you would need to increase your piston to cylinder wall clearance due to lessened silicone content.

GOOD LUCK