Why My Engine Backfires?
 

Why my engine backfires occasionally when going slowly with no throttle, for instance driving downhill?

Are you sure this is a backfire and not the typical burble of off throttle engine braking? Is this 930 new to you or have you recently changed the muffler to something less restrictive than OE? CIS continues to pump fuel when off throttle, that excess fuel can ignite in the hot muffler. Quiet mufflers silence this.

also check for exhaust leaks at the heads.
make sure intake bolts are tight.

Thank you for explanation - makes sense.
No, it was always like this for 8 years since I got the car. I just was not sure what it was.
How backfiring would be different?

OFF TOPIC, CAUTION:
I have similar sound on my Yamaha cruiser (V-twin) which obviously is not CIS. It was not there till now. What could that be?

air leaks in exhaust most likely