Small Engines (Lawn Mowers, etc.): knock in engine, blown head gasket, crankshaft pulley

Question
I have a Briggs 20hp model 351777 engine. The last time I used the mower the engine started to knock as I was mowing. The engine lost power but would restart. The knock is still there. What could this be? Thanks Dean

Answer
 Hello Dean:

 A Connecting Rod. A Blown Head Gasket Depending on Where it Blew. Loose Crankshaft Pulley. Loose Engine Mount Bolts. Carbon On Piston Top Hitting the Cylinder Head. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John