I have received a lot of great information from this site and thought I would utilize it to get some help with my problem. My sons Tao Tao 110cc atv over heated. Hot to the point it didn't have any power and then stalled out. It has not started since. It cranks but does not start. I replaced the carb and spark plug. Changed the oil, fuel and air filter. Still nothing, even with starting fluid. It has spark when putting the plug onto the block and also has good compression coming from the spark plug port. I adjusted the valves a few prior to over heating so maybe they need adjusted again?? I am out of ideas. Like I said, it has compression and spark and cranks strong. Could I have a fuel issue?? I don't see damage to fuel lines and gas flows freely from the tank, through the fuel filter and into the carb. It also gets smoke out of the muffler and park plug port after it turns over several times. These are all new issues since it over heated. Prior to that it ran great. HELP!!

 

"also has good compression coming from the spark plug port." How good? If an air cooled quad engine gets that hot it usually seizes on the piston, this drops compression and the engine won't re-start after it cools and frees off. 90 psi is about the minimum for starting.

 

Should've got a Venom 125cc ATV from belmonte bikes :P

https://www.belmontebikes.com/collec...nt=18281416513

 

Not quite sure how that's helping this forum member...

 

I've had that issue before where my ATV wouldn't turn on. It had spark when putting the plug onto the block and also has good compression coming from the spark plug port. Checked everything and replaced everything to make sure I didn't miss a step and still wouldn't turn over.
Went back to basics and I checked the fuel I had in the gas tank and for some reason the gas station I filled up the fuel from was watered down!!! The gas was almost white!!
Drained it, replaced it with premium fuel and fixed the issue right away!

I don;t know if this will fix your issue but if you've tried everything, it's time to go back to basics. Worked for me

 

This doesn't help. This is a member with no knowledge. Only opinions. Thank you to all members who have gave intelligent input.

 

Any updates here?

What is the compression? Have you run a test? My first thought was warped head, etc...from the overheat. It might feel like good compression, but maybe it is leaking and too low to start? I don't have much to offer in the way of valve adjustment.

 

I did a test and had lower compression than I thought. Changed the piston/rings and all gaskets. It fired right up after doing this but it still over heats. Really fast too. After idling for 30 seconds it is extremely hot and smoking. I am thinking it could be an exhaust valve issue. The smoke comes from around the cylinder head and exhaust so that is leading me to believe it is overheating at this location. Do you agree or have other suggestions before I tear the motor down again??