Re: my pics
Nice engine Shane.
Sometimes unexploded gas can explode in the muffler. I have had it happen, I seem to remember there was rust particles in the carburetor and some times partially blocked the jet causing a misfire with a build up of gas in the muffler and exploding just as the exhaust valve opens after ignition in the cylinder. My hot bulb Hornsby also started doing it when the hot bulb cracked. A new hot bulb fixed that one.
Merv