Intermittent Misfire/Stumble

[bicyclenut]

Have a 2010 R1200RT with about 127,000 miles on it. Rode it down to a Rally in Lebanon, TN this past week and it seemed to be running a bit rough at highway speeds after riding about 250 miles from Chicago area to Indy, at first I thought maybe just road surface. Once down in area I noted that the idle was not as smooth as usual and starting was a bit rough, not as quick and definite as before on acceleration. When riding I found a pretty consistent misfire or stumble, mostly under load, required more throttle off the line and worse when hard acceleration or up grades. At cruising speeds, maybe 4000 RPM, you would notice a regular stumble/misfire. It pretty much did this for 2 days of riding about 500 miles around the area. On Saturday was caught in the isolated heavy rain around rally site and when riding back to hotel the bike miraculously ran like normal, pretty smooth for a bike with 125,000 miles. You would expect moisture to have the opposite effect, causing a misfire and ignition issue, etc.I also noted more exhaust popping/backfire on engine braking when decelerating and sometime when changing gears.

For reference spark plugs were changed at 114,600, and coils were changed at 65,300 when I noticed a misfire/stumble at highway speeds, less frequent and a bit different than this as only noted at higher speeds in gears 4-5-6.

My first though was had to be a coil issue. I had coils in my cart at EME and ready to order before I rode back home so they would arrive this week. But after Saturday and the entire 500+ mile trip home Sunday, the bike was smooth and rode like normal, no misfire, no stumble.

Anyone else have something similar? Any suggestions or ideas? My gut feeling is to replace the coils and maybe just do the plugs at the same time even though a bit early as interval is 24K.

[Stu]

I wod be looking at the plugs to start with

[480VAC]

I’m having what sounds like a similar issue. In the spring, I was riding in the rain and the engine would run beautifully up to about 4000 rpm, at which point it would abruptly start misfiring and stumbling. I had to ride the whole way keeping under 4k. after the bike dried off, it was fine for many months. I was driving to winter storage and it happened again last week, it was completely dry out, but cold, close to 0. it would not rev above 4000 but ran beautifully up to that point. I stopped for gas, and when i started riding again the problem was gone. To me this clearly indicates something electrical, since any fouling would not happen at a very specific rpm.

Any suggestion from the wise?

[Stu]

Start with the plugs and the coils

[bicyclenut]

I did replace the coils and the spark plugs at the same time. Plugs didn't look bad, typical bottom plugs had some signs of maybe burning oil but non were really beyond normal wear. Based on my previous experience I'm sure it was a coil. Have put about 6000 miles on bike since the issue this summer and no issues, runs great as it did before.

[Randyjaco]

If those suggestions don't solve it. You might take a look at the valves and cams. Hopefully it is not Chocolate Cams