Loud Popping Noise From Exhaust

I filled up my radiator, and ran my bike to let it heat up. It did just fine, but then I turned it off, and a huge BANG came out of the left exhaust pipe. It sounded like a gunshot. I'm wondering what the sound could have been, and if it's all right to start it back up.

 

I have a 98 with a Two Brothers high mount exaust. Bought it that way. Not sure if any tuning was done after the change in the pipe. I occassionally get the odd "pop" or backfire. Performance is great on the bike. I woudn't be too concerned. JMO.

 

Do you have to fill the radiator a lot? Are you losing coolant? Does it have stock pipes? If you have stock pipes you may have an exhaust valve leaking a little, putting gas into the muffler. When you cut it off, the gas in the muffler exploded (BANG!!). If you have open pipes, it wouldn't be uncommon to get the occasional BANG.

 

I have stock pipes with an inch wide hole. I don't think I'm losing any coolant though. I checked everything, and it seems to be running as good as before, but with a very frightening backfire.

 

I'd start with a new set of spark plugs. That's a cheap place to start, and my Sabre took a spell backfiring, changed the plugs and it quit. Second, if it is still doing it, you may have an exhaust valve leaking. Check the compression in all cyls and compair the #s.