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.