Husqvarna 272xp exhaust coming out of the carb

[Fettlst]

hi, ive got an issue that ive never come across before. I have a 272xp that ive rebuild and when i try to start it it may run for a few sec and then "pop" exhaust out the air filter and die. anyone ever had this to happen? Thanks

 

[motosierra]

It can't hurt to double check the two gaskets between the carb and the cylinder.

 

[Crofter]

check that the muffler is not plugged.

 

[HiOctane]

Keyway?