I got a problem with my engine, it is very hard to start and when it finally starts i can run a few laps when it cuts out again and is again very hard to start. We thought it might be the plug so we changed it from an novarossi c6tgc average to a c7tgc cold plug. This didn't help. i also replaced the fuel lines (Which i do before every race) checked if the flywheel was hitting something which wasn't the case. I also checked the clutch and it looked good.

I checked the carb and cleaned it with fuel but there wasn't any wear i could see.

Does anyone have any other suggestions that i can try? As i am quite confused what to do now.

I have attached a picture of the engine.