Kevin’s Dirt bike. Engine seized

I'm 16 years old and I've always wanted to have a dirt bike but i couldn't afford one until I was 15 and it's my first bike and i always dreamed of racing but as soon as i was good enough to begin racing my engine seized up with the engine only having 90 hours of run time even though it's supposed to last over 200 hours and none of the mechanic shops know how it could have happened. And it costs 700$ to fix and I can't get the money because my car broke down with a blown piston. I would be very grateful if i got some help. Racing has always been my dream and I wanna get my bike running as soon as possible. Thanks