My kid has a Chinese atv. Has the 110cc engine. Ran great last year till end of year then wouldn't start. It was then stored for the winter. Got it out this year and cleaned the carb. Still no start. Has spark seems to have compression(don't have a tester). Cant find my feeler gauges to check valves but when valve is closed they have very little clerence but are rockers are moveable. If I hold the throttle WOT while cranking it will sometimes fire up for a second.

 

NVM guys got it going ended up the plug was cracked or something... If I grounded the electrode tip while testing spark it sparked correctly.. but if I grounded the threads of the plug instead it would never spark to the tip of the plug.. replaced plug and it started fine

 

Following!this seems like a very interesting thread