What fuel are you using? These Enyas have a cast iron piston and need around 25% all castor fuel. You might get away with some synthetic but I wouldn't use any in mine (I've got a 35). Originally they came with two cylinder heads, a high compression (9:1) and the low compression (7.5:1) but I'm not sure which one they were assembled with. I'm with big max though, it sounds like a bad fuel problem.