I have a B&S model 310707 engine in a riding mower. It was running fine . I shut it off and the next time I tried to start it it revolved about 3/4 ways around and went CLANK! Wouldn't move any further. When I backed the engine by hand and did it again , it went CLANK again and stopped exactly where it did the first time. Definitely sounds like metal on metal and a very solid CLANK. Any idea as to what it is and whether someone with reasonable mechanic skills could fix it?

broken rod. Camshaft to piston. Engine was run without oil.

Did that once when I was 10-12 yrs old. Won't do it again. Dad said your rebuliding it. With a little guidance a 10-12 yr old can do it.

Hech, I was doing paint by number of three 2' x 3' paintings when I was 6 years old.