wsmm.........uh? you do know yer #4 exhaust leak has 'nuttin' to do with engine not starting, don't you?
While ATF is good stuff and will "un-stick" stuck piston rings, you do know iff'n either the intake valve ...or... the exhaust valve fer #2-cylinder are stuck OPEN, guess what??? NO COMPRESSION. The N-Engine is very good, it will generally start on just 3-cylinders, just need sparkies at the correct cylinder at the correct time. Many neubie shadetree mechanics miss-plug the weird 4-nipple frontmount dizzy sparkie wires. Firing order is 1,2,4,3 CCW. Suprizingly enuff the 4-nipple capple has MOLDED sparkie numbers, just plug as numbered. #1 sparkie is next to radiator. Simple, eh?
It is very eazy to FLOOD yer M/S carb, so ennytime you have starting issues, replace yer sparkies. NO ARGUE!!! Recommend AutoLite 437's gapped 0.025". Don't throw yer FLOODED sparkies away, just clean'n'dry them one-atta-time in HOT running engine; and save'um fer the next time. (and there will be a next time)
You ask what the float setting should be? Would you believe 1/4"??? (I use a 1/4" drill) .........Dell, yer self-appointed sparkie-meister