I know this may be WAAAAAY too simple, but I had the exact same problem with an Alpha 40 running the kit included Evo engine. I replaced the glo plug, pulled the tank, checked all my fuel lines, clunk, blah, blah, blah. How old is your fuel? Methanol attracts moisture. If your fuel has any age on it, especially if you are getting close to the bottom of a gallon and it has been exposed to heat, say at the field, moisture droplets will condense inside the fuel container and literally water down your go juice. If you haven't found a fix yet, try a new gallon of fuel.

I'm very new to the sport, but just something that I have picked up so far. Hope it helps!