89 yamaha moto 4 250

Im having problems need help.
the problem is it wont crank
i have good spark and im getting
fuel but wont even try to crank
i can shoot a little either to it
and it will try but will not crank
so any help would be helpfull thanks  

Kinda sounds like what mine's doing too, I think my timing chain may have slipped off the lower gear or something, good starter and it's trying to crank but seems like something just isn't catching good enough to turn it over by itself...I took the passenger half of the engine apart and found nothing wrong so I think it's on the left side where the timing is...They recently put a new timing chain tensioner or whatever it's called in before I bought it and shortly after, I think the chain slipped or something and now it won't catch...  

have you tried cleaning out the carburetor?

if not check out the carburetor cleaning 101 post under atv repair and maintenance  

Get a compresion tester and check the compresion should be at least 80 lbs.