Originally Posted by JonJay
What caused the fire?
Ok, assuming back fire into rich airbox.
After several reports of this occurring, with or without drain holes, I modified my cold start procedure. I no longer prime my injected engine, which can dump fuel into the airbox. I simply crack throttle, mixture rich and then backed off a few turns, hit the boost pump, listen for pump to load (two seconds or so), then crank.
Starts within 6 or 8 blades. Doesn’t cough and choke like it used and risk of an airbox explosion event is reduced or perhaps eliminated.
Hot Starts are done the same way with the exception that the mixture is closed, no boost pump, throttle cracked, start cranking, and advance mixture slowly and it will fire.