Backfiring and momentarily losing power. 1981 R100RS

[norton]

Looking for some direction on this bike. 11,890 original miles, and has always run well. On a ride a week ago the bike had an intermittent backfire and one complete power loss for 2 seconds. It came back to life and had another backfire while slowing down for a light (kept running). I road the bike another 50 miles with no issues.
Plugs, ignition wires seemed fine
Plenty of fuel
I haven’t looked at the Bings, but it had a complete tuneup @ 9,000 miles
This bike comes with electronic ignition from stock

 

[20774]

Heat paste need to be renewed on the ignition module?

 

[stevenrankin]

Gunk

Possible Gunk or water in the gas? St.

 

[beemermark]

Possible Gunk or water in the gas? St.

I second water in the gas. Try a new tankful.

 

[pglaves]

I second water in the gas. Try a new tankful.

Add a dose of IsoHeet in the red bottle, or at least Heet in the yellow bottle.

 

[stevenrankin]

Pollywogs

Water can be spotted by pulling off the float bowls and looking for the distinctive gloop, pollywog, or blob of it at the bottom of the gasoline. If it is there, Paul has the best idea, if it is real bad, drain the tank and get a new tank full.

Not to be a jerk but, how does the inside of the gas tank look? A 81 with only 11K miles has not really been run very much. If it has sat with gas in the tank, it could have varnish or worse yet rust. A quick look with a flashlight can tell a lot.

If the bike is pristine, I apologize for bringing up the topic. St.

 

[beemerguru]

You've already heard water in gas and ICU paste.

Did you happen to notice if the tach went to 0 during the cutouts? If so, then ICU paste or bean can..The Hall senser usually last 75+ miles or more..seen 130K on an original..but it's another place to examine.

Or the ignition or kill switch...but a low mileage bike wouldn't go on that direction unless there's some (lots of) corrosion.