Originally Posted by
Sport_Pilot
Sounds like a muffler pressure issue to me. Check the pressure nipple to see it it's clogged. Does the muffler have enough backpressure?
It worked in the past, but I will check the fuel nipple and tubing tonight. I never had this problem before with this or any other engine. That's why I'm stumped. This muffler is fairly restrictive like the stock muffler.
The reason I did not suspect any fuel plumbing is because the engine idled and transitioned perfectly. It even ran WOT perfectly until tipping up the plane vertically.