I had a problem with an OS25LA engine last weekend. After priming the engine to start it, attaching the glow starter, and applying the starter to the spinner, the prop turned as if to strart, but froze to a stop after spitting fuel from between the cylinder head and cylinder in the back.

Weirdest thing. If I just turned the prop by hand, no problem, it feels normal. The second I used the starter on the spinner....it freezes up after a short few seconds of spinning, spitting out fuel from the back.

What could be the cause? and what's the repair?

Thanks