cold start / kick start problem

I have a baja dr 90cc dirt bike with a sheng wey carb, i am having trouble getting it to start, i can start it if i push it down a hill then put it in neutral (after it has been started), but it has no power till its been warmed up (15-30 min) then after that i can kick start it and runs like new. any suggestions? I want to be able to take it places but would need a hill just to start it.

Back ground: wouldn't start at all till i put Teflon tape on the main jet screw and turned it out 3/4 turn, so i jetted it , it had a 72, so I replaced it with a 70 and starts when being pushed down hill. i have messed with the air / fuel mixture to get it running as best i could and adjusted the carb needle. choke doesn't seem to do anything, used to start and run fine, has a new spark plug, and carb is clean. i can upload a pic of the carb or i can take a video of me starting it down hill if needed.

any help would be great!
Thanks,
T.K.

Valve clearance within limits ?

Thats the only thing i didn't try, would it run poorly even when it is warmed up if they were out of tolerances?