Maintenance such as not cleaning/changing air filters along with years of wear and the nature of two strokes to begin with. The top ends will never last as long as in a 4 stroke engine. Again compression can be the problem or possibly a leaking crank seal behind the drive clutch. If you've got good spark now, it has a good fuel supply to the carb,then move on to the next step as most manuals state and that is to check the mechanical part.

 

My 20+ year mechanic/electrician friend came over and is absolutely baffled, he sprayed starting fluid straight in the throttle hole on the carb and sprayed in through the air intake and it came out the throttle hole and the engine spit a little gas on his hand when he put it over the throttle hole

 

Again check compression,then check if the seal behind the drive clutch has popped out! It wont run at all if it has..

 

Tbh I don't own a vacuum pump and my mechanic friend said the drive clutch seal looked fine but as soon as I know the pressure in the bike I'll let you know if it's above 100

 

I’ve replaced the CDI box ignition coil and have no spark did everything suggested in this form still no spark. I replaced the stator earlier this year. When I do an ohms test on the exciter coil it reads zero. do I need the engine cranking when I run the test ? This all happened while I was using the override in reverse the ATV died. Now no spark :/