04 speedmaster right cylinder backfires

could be a bad valve intake side of headdoa compression test to make sure cylinders or reading above 100 lbs per cylinder

do you have ignition on the right side ? it's just an idea but check the sparkplugs on the right side they might be faulty...

muffler explosion
#1 reason , EFI running rich as a pig (CEL glowing and warning)
and exhaust cracks, (adds air )
air + fuel = muffler explosion and can blow the whole thing to H3LL
pipes blast off. car.

possible issues in the area containing - Camshaft, pushrods, valves, rockers, and the valve springs.

Im having similiar issues with a carburated V8, runs great, but backfires, then now it seems like maybe its trying to air lock, or essentially maybe a valve is not opening any more so it cant freely turn over when I try to start it.. So i would maybe inspect the cylinder head and all those components

I would run a compresion test on it first

the fuel is lean on the bottom, i dont know if the power commander can add some fuel or not. Why disconnect air injection, also if disconnected is the exhaust leaking.

pilot jet blocked, remove air filter and blow wd40 through pilot air hole (5mm hole at bottom of venturie) or dismantle and clean.

Triumphs have a habbit of the ignition coils failing past a certian age. Switch the coils around and see if the backfires transfer with coil.

clean spark plug an gap it to .025inch

if still backfiring reset timing / points

1. Did you clog your airfilter with gas or anything else when you rolled it?
2. Did you damage the petcock or fuel control?
3. Choke cable stuck open?