Briggs 406777 0128.E1 tractor was givin to me because owner said it no longer ran. He replaced the carb and magnetos to try and get it to run, but upon cranking, this engine spins, spits and sometimes emits a small fireball out the air cleaner. Things I've done to make it run:

Removed heads, Lapped valves and seats- valves are now good

Removed engine, replaced governor

Put original carb back on after cleaning it

Replaced plugs, pushrods are fine

I can now get the machine to idle only if I hold linkage to close carb all the way, either way it will not throttle up by any means, it just dies........... This one has truly stumped me.. Any thoughts?