I bought a ATV that "only" needed the valve seals replaced to make it start but ive changed them and it still wont start. it has compression, gas, and spark ive checked the timing 100 times and it is right. anyone have any suggestions?

 

Which timing have you checked? If the flywheel TDC mark is not actually at TDC by the piston, this will throw ignition timing out, and valve timing if you used that TDC mark to set it. Valve seals wouldn't have stopped your engine running anyway, just made it a bit smoky on start up. If TDC mark is correct, then fault can be air/fuel mixture, it needs to be near correct to start. Unless someone has been altering things, most likely fault is dirt in carb, so clean it out, blowing jets and the holes they came from out with compressed air. A weak spark can cause problems, not easy to tell, Suzuki LT50s seem to have the weakest white spark, but run fine. Fit a new plug anyway, just in case.

 

Make sure your Valve clearance isn't to tight, they must have a slight movement up n down at top dead center.

 

have you checked the compression with a tester? i rebuilt my 230 years ago and didnt hone the cylinder when i was young and inexperienced and it felt like it had good compression. but i had to roll it off to start it. and it wouldnt idle. then years later i honed the cylinder and didnt even change the rings. and it kicked like a mule at that point. super strong compression. and it runs and idles perfectly now and has for a number of years