OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Knocking sound on B&S after blade collision

Hi guys,

I hit a metal object with my B&S classic mower (solid bar blade), and now it makes a knocking noise when its running.

The flywheel key is intact, and the crankshaft doesn't look bent... so what else could be wrong with it?

~Mike.

Have you pulled the flywheel off to check the key?

Yep, took the flywheel and key off but they look okay.

You might have bent something internal, maybe conrod if it was on the power stroke when it hit or damaged the gudgeon bearing. Those solid bar blades are probably the worst thing anyone ever came up with.

My experience is that blades are usually bent during these and be hitting the mower deck afterwards. Of the ones here that have been in these mishaps the crankshaft is usually bends out the crankcase. I have yet to see one with internal damages. This does not mean it can't happen. A good way to tell the crankshaft is bent is reference the blade center mount bolt as you rotate the blade through one complete turn. one other thing to check is blade mount itself as normally they are also keyed and one slipping may cause the knocking noise.

Note: We here in the US have used what you call bar blades as long as I can remember on push mowers and I am now 58 yrs old.

I might have a look inside to see if anything is damaged,or loose. Thanks for your help guys. mike.