If your compression is good (good piston & sleeve and all bolts & the glowplug are properly tightened) and you don't have any air leaks the only things that could be wrong would be trash caught in the fuel line at the carb, etc. (clear the problem and use a filter), bad fuel or you need another glowplug. Personally I use OS #8 glowplugs in ALL of my 2 cycle glow engines. I used to use Fox R/C long glowplugs but found the OS #8 glowplug offered better overall performance.