Blaster motor problems

[Bob]

I have a 2005 YFS 200, rebuild engine, replace crank, rod and piston. After about two hours of running and running very good the engine stopped and will not start. It is getting gas, has spark, and has good compression (130 psi+). Checked timing and electrical system and found no problems. When you try to start it will just pop about every ten cranks. Have been told that maybe have a vacuum leak between the case half’s but do not know how to validate that possible problem. Any suggestions on what to look for next?
Thanks
bob

 

[Larry's Shee]

How are your reeds? New? Search "leak down", can build one or purchase one from a member on here, can't remember name.
BTW, Welcome !!