I bought a ys 63 a while back and have just started to regularly use it. I am running it on 20% yamada mix model-technics fuel in a h9 funtana. Its running a 13x6 prop and has had aboutt 2 gallons through it. Yesterday after 3 flights it wend bang and suddenly stopped. There is now very little compression. I havent attempted to restart it after the bang. Where do i go from here?

Thanks in advance

Pull the valve cover and see if it dropped a valve. If not, check the valves for correct adjustment. Also check the cam gear to see if it has lost some teeth.

Let me know what you find.