Managed to snag a used 110 ATV about a month and a half ago. Changed out the carb upon purchasing and it ran flawlessly. Put new oil in and new gas. Last week, was running full throttle down the street and the engine sputtered as if it wanted to die but I was able to keep the engine running as we slowed down to get to the house. Once we got to the house the engine could not turn over at all. I replaced the CDI after doing some ohm readings but I was only able to get about a quarter of the RPMs that we are used to seeing when the engine actually turned over. After that, started to adjust intake valve to 6 thousandths and exhaust valve to 9000 thousandths. After the adjustment, barely got a sputter out of the engine but no full turn over. Not sure where to go from here. Any guidance would be hugely appreciated.

 

Please don't use the term "the engine could not turn over" it literally means the crankshaft won't turn, ie, the engine is seized or starter won't work, but your post doesn't make sense if this were true. Did you check for a spark before assuming an ignition fault? As a blocked carb or water in the fuel is at least as likely cause of those symptoms. I always change the plug, just in case but, after checking there is a spark, would clean the carb out next.

 

Thanks for the info on terminology. That's good to know. I've used 2 new spark plugs, both of which are sparking. I haven't checked the carb as it is also brand new. Gas is also fresh but I'll check on that.

 

"I haven't checked the carb as it is also brand new"

Unless fitted since the problems started, it could have pulled dirt through from the tank. If it won't run with a clean carb, I would be checking compression next. Much under 90psi and engines get bad to start and gutless when they do run. A light seizure when "running full throttle" would cause a drop in compression.