if it pops in the exhaust, it is just unburned fuel that has gone thru the cylinder without ignition but then is ignited in the pipe when you start the engine.
The plug wires also rub on the small, steel, sharp plate that holds the coil to the coil cover. It is a plate with sharp edges and has worn my plug wires as well. I put my orange Taylor wires back on because the stock ones were worn pretty bad.
That is probably the culprit to the last (the very LAST!) three EHC's that burnt up in the bike.