Engine popping

I was given a troy built mower with 17.5 b&s engine. Mower shut off while in use (this is why I got it). I found the intake valve gap was about 1/4 of a inch. Adjusted it to .06 and tried to start, will not start--buts popping out of carb and exhaust while cranking. fuels looks and smells good. Key in flywheel not broken, but does seem to have low compression. suggestions anyone????

Are you sure that you adjusted the valves correctly. With the piston a slight down stroke on the power stroke, with both valves closed at the time.

Other possible problem could be blown head gasket.

Post model xxxxxx, type xxxx, trim xx from engine data plate.