need help with idoling

[300racer]

i just got my motor together and when i start it and it's idoling it sounds like it doesn't fire every time. and eventually will die. when i rev it up it doesn't do this. my buddies 450 does the same thing. does anyone know what causes this than how to fix it?
both bikes are 05 if that make any differance.

[WilRideAnything]

Are the valves adjusted properly?

[Jersey450R]

idle

[300racer]

the valves are probably the problem i have not checked them since i put the motor back together thanks alot.

and thanks for the spelling check lol.