I would recheck your glow plug.. Also make sure your glow driver is fully charged. . Its so hard to say because there are many little things to check and with out being there and seeing how your engine is mounted ,your fuel tank location etc. etc. all a person is doing , is just guessing .. If your engine is inverted it is very easy to flood the plug and then very difficult to start with out a real hot glow driver ..I have accidently hooked up the wrong line to the carb before ...Are you using your muffler to pressure your tank ?Four strokes like to be well primed to start .. Are you priming ? Can you feel compression when you turn it over ? It could have a stuck valve . Although I would like to help you I think the guys at your club might be a better help because they could see what's going on ..