Small Engines (Lawn Mowers, etc.): 24 hp brigs with valve issues, overhead valve engines, vanguard engines

Question
I have a B&S 24 hp intak
445677 type 0413 E-1   code 050614 YH
Thought we had a bad head gasket.. discovered it was a bent push rod. Replaced it.  Engine started ok but when I engage the blades ... loud knock... with white smoke.. also does it under heavy grass load...  Son adjusted valves.. he thought..
strangest thing yet.. when we shut it off... it kept on running.. even pulled off plug wires..kept on dieseling.. finally put it in gear... it stopped.  
I know we have to re-address the valves...  would bad adjustment cause that knocking?

Answer
Dan
With the new Millennium, the engineers at Briggs & Stratton felt it was time to come up with a new generation of engines called Intek for the lawn and garden industry. These engines lead the field in innovative design and borrow technologies from their older brothers, the world class Vanguard engines. Horizontal single cylinder overhead valve engines, rated at 5.5 to 11 hp with a 30° slant. Vertical models come in 6.5 to 17.5 hp single cylinder and 90° V-twin vertical overhead valve engines with full pressure lube and oil filter, rated from 22 to 26 hp. These are just a few of the new design features available to the consumer lawn and garden equipment market using the new Briggs & Stratton Intek engines.A bent push rod means that it came to a stop before it went all the way in or out.  It was on the valve end or the camshaft end.The keeper may have come off and jammed the valve.  Be sure to check it out completely.

So having this information you have a v-twin which has 4 valves 2 exhaust and 2 intake which have to be timed for the engine to correctly run. here are some solution's.

I called Briggs and was told to set the valves to .005 at TDC on both intake and exhaust.
Try pulling out the choke a little, if it stops backfiring the mixture is too lean, check the intake pipes at the cyl head and also the plastic runners to the carb for leaks.

I'd also recommend checking the torque on the head bolts. I just replaced a blown (really just small cracks) head gasket on the same engine.The engine went less than 200 hours before it started burning oil. The oil was (it appears, It have only a few minutes run time on the new gasket) getting into the combustion chamber from the pushrod area due to a leaky gasket.