More Suffolk punch problems!

Hello again,

Bren going great guns with my mower, until today when the pull cord snapped on restarting the mower after emptying the grass box. No bother, easily fixed. But then , would she start again? Would she hell. 

Carb off - cleaned. Only professionally cleaned a few running hours ago, anyway. Same problem. After some effort get the following 

Full choke. No start

Half choke - starts rough. 

Either half choke or no choke, apply revs and nothing happens. Stays ticking over. Then, all of a sudden - bang - full revs for a few seconds - then back to idling. 

I seem to feel some exhaust from near the outside of the valve chest area? Could of course be a hole in the exhaust muffler.

Took head off. The intake valve is coked and doesn't seem to rise as high as the exhaust. (Note when I bought the mower the intake valve was seized closed). 

Also seems to be missing a head gasket now I notice. Ordered one. Also as a note, the carb to engine block gasket is split. (Trying to find a new one)

Any minds cleverer than mine able to diagnose this symptom?

Thanks in advance again!