ok so ill try and make this as short as i can i really hope someone here can help me figure this out...
bought a 2001 Mojave 250 from some one not running.. was running till ??somthing?? happend. was told before it stopped running it had a timing chain slap sound so the chain was replaced.
got the quad home and did a compression test results were 0psi...lol decided to break the engine down n see whats going on. found a brand new timing chain installed and yet 2 valves pushed into the head..so i ordered a top end gasket set and all new valves and lapped them in. while the head was off i did a broke man leak down and filled the cylinder with thin oil and let it sit for a few days and none of it leaked so i assume the rings are good. reinstalled the head with new head gasket and valves. re did a compression test and I'm seeing 80psi(i don't really trust my cheap tester). I kick start the quad over and it will run for about 10 seconds and then die. I'm getting good blue spark. cleaned the carb and tried again... i can kick 10 times and it will only start for 10 seconds or so. swapped my carb, throttle cable & thumb throttle from my 87 Honda 250x to the Mojave and same result 10 seconds... had a friend bring over a known good working Mojave carb and you guessed it same results 10 seconds. even swapped to a back up stator that i have and same thing... what in the world is going on! i dont know what els to try

 

Try a new plug, even if the one fitted is new. Check that TDC by the timing mark is TDC by the piston. If OK, re-check the valve timing mark is set right. Re-check you got the valve clearances right. If all is OK, check compression now. If it is still low you may need to take the top end down again and check the valves were seating properly, and remove cylinder, check the ring gap on the top ring, and the piston for scoring.