Join Date: Feb 2013
Location: New York
Thanked 1,236 Times in 1,141 Posts
If it's got spark, and the key isn't sheared, my bet is the compression is still low. Briggs flatties with no compression release usually hit at least 90-100 psi. If it had enough compression, it would pop on ether or carb spray. Could be the rings/aluminum bore are worn, the valves needed to be resurfaced before being lapped in, or I guess it could be the head gasket if you didn't throw a new one on there. If you wanna keep chasing this, you might have to look into a ring job or getting new faces cut on the valves/replacing them.
One last thing, did you squirt the ether directly in the spark plug hole? That way you know it's in the combustion chamber 100%. Don't even have to tighten the plug more than hand tight; just get it in there and rip the cord a couple times. If it doesn't even try to start, you're almost certainly not building enough compression.