Weird issue with my '03 savage.  The engine will crank and has compression but won't start.  After about 3 attempts, a pop occurs and exhaust shoots out the carburetor air filter instead of the tailpipe.  

This first occurred back in May.  I checked compression and it was lower but still within spec.  Fearing a valve issue, I had the cylinder head inspected at a machine shop and had the valves serviced.  I replaced the head gasket and reassembled the engine, charged the battery with a charger, and cleaned the carburetor.  Air filter is a Emgo cone.

After all this, it is there is still a pop after 3-4 cranks and exhaust still shoots out the carburetor.  

I am stumped.  It has a straight pipe exhaust and verified it is not blocked.  Timing has also been verified.

Suggestions would be greatly appreciated.  

Thanks!