Engine running rough after hitting a stone?

I have a rotary petrol mower, powered by a Briggs & Stratton HP470. Yesterday I hit a kerb stone and the engine stopped dead.

I retarted it and it sounded really rough and was vibrating. I removed the cutter blade and bent it back to level, sharpened and balanced it (as best I could).

Upon re-starting it sounds like a bag of spanners! No smoke but really noisy, rough and the engine speed is uneven.

Have I wrecked the crankshaft bearings or can ayone suggest what else it might be please?

Griffo
May 2009