Rough idle 1995 R1100RS

[bmwdr]

I’m bumfuzzled. Finishing my 84k service, after fluid changes, new plugs, fuel filter, ig timing, adj valves. Took an initial 10 mi. ride, topped up with a gallon of 93, all was great. Then finished by checked throttle cable slack (no change other than 1mm choke slack) throttle bodies opening in sync. But now it has a bad idle with misses & backfires at tailpipe and snorkel. Adjusted valves again, still bad idle, but runs clean once warm and past +-2,000 rpm. Still cuts out at idle. Any thoughts?

 

[pglaves]

I’m bumfuzzled. Finishing my 84k service, after fluid changes, new plugs, fuel filter, ig timing, adj valves. Took an initial 10 mi. ride, topped up with a gallon of 93, all was great. Then finished by checked throttle cable slack (no change other than 1mm choke slack) throttle bodies opening in sync. But now it has a bad idle with misses & backfires at tailpipe and snorkel. Adjusted valves again, still bad idle, but runs clean once warm and past +-2,000 rpm. Still cuts out at idle. Any thoughts?

I have two thoughts: First, did you carefully synch the throttle bodies at idle using the air bypass (Big Brass) screws? Second, are you positive of the valve adjustment being very precisely correct.

A problem with either of these steps can cause your issues.

 

[dieselyoda]

Don't bet money that those new plugs aren't an issue.

Just did a pony engine and new plug. Didn't start or just popped like a bad exhaust valve.

No need to a compression test or a cylinder leak down.

I did the engine.

Dropped a new plug in and ran great.

Plugs be cheap, my experience, gassers, change the plugs as your first step.

 

[BC1100S]

I’m bumfuzzled. Finishing my 84k service, after fluid changes, new plugs, fuel filter, ig timing, adj valves. Took an initial 10 mi. ride, topped up with a gallon of 93, all was great. Then finished by checked throttle cable slack (no change other than 1mm choke slack) throttle bodies opening in sync. But now it has a bad idle with misses & backfires at tailpipe and snorkel. Adjusted valves again, still bad idle, but runs clean once warm and past +-2,000 rpm. Still cuts out at idle. Any thoughts?

Ensure the throttle cables are properly seated on the throttle body.

 

[52184]

Ensure the throttle cables are properly seated on the throttle body.

And also make sure the enrichment (”choke”) cable is properly seated and not hanging up. That adjustment was mentioned as one of the last things done to the bike before the problem surfaced.

Best,
DeVern

 

[Paul_F]

You also added a bit of gas. On one trip my 1100 was running fine until I filled up with what I later suspected to be bad gas. At the next stop it back fired and the idle was erratic for the next several days. This may not be your problem but something else to consider.

 

[RPGR90s]

I’m bumfuzzled. Finishing my 84k service, after fluid changes, new plugs, fuel filter, ig timing, adj valves. Took an initial 10 mi. ride, topped up with a gallon of 93, all was great. Then finished by checked throttle cable slack (no change other than 1mm choke slack) throttle bodies opening in sync. But now it has a bad idle with misses & backfires at tailpipe and snorkel. Adjusted valves again, still bad idle, but runs clean once warm and past +-2,000 rpm. Still cuts out at idle. Any thoughts?

Those are tell-tale symptoms of one of the throttle cables not being seated in the ferrule. Happens quite often doing removing of the panels.