Stumble in power around 5,500 rpm during hard acceleration on 2011 RT

Has anyone else experienced this? I have changed plugs and air filter (both

were in need of replacement). Acceleration seems normal throughout range except for full throttle

somewhere between 5&6k rpm. About 33k mi on bike. I've owned it since 2k mi and have noticed this for awhile.

Has anyone else experienced this? I have changed plugs and air filter (both

were in need of replacement). Acceleration seems normal throughout range except for full throttle

somewhere between 5&6k rpm. About 33k mi on bike. I've owned it since 2k mi and have noticed this for awhile.

Afternoon izquik

EXACTKLY when did the problem start?-- That might help us narrow it down.

If it started after the last fuel fill up then it could be a gasoline octane issue. (the older 1200 hexhead bikes had 5-6K acceleration issues due to low octane gasoline & knock sensor calibration issues)

Might also be an upper coil starting to go out.

Or possibly an FPC not allowing full fuel pump output.

Might even be a park plug problem.

Maybe with a little more info we can get closer to the problem root.

What a coincidence. My 2005RT does the same thing. Only on full, wide open throttle. First time I noticed it was on my first ride of the year.I went to pass a truck in 4th gear and at about 4500rpm, the bike jerked about 2 or 3 time like it was missing something. Only on wide open throttle. As long as I backed off a bit, it was fine.

I took it to the BMW dealer, whose mechanic I have full confidence in, and he replaced the plugs, swapped coils, adjusted the valves and TBS, balanced the temperature etc, etc, etc. I'm not sure he did anything with the FPC but did averything else he could think of. He and I both took the bike for a ride, and now it "stumbles" between 5-6000rpm. Not quite as badly (sometimes) but only on WOT. The only other thing he could think of was maybe a new wiring harness if it gets worse.

We just finished a 4 day trip and it didn't bother me but I didn't push it too much either. I may just live with it if nothing works but it sure would be nice to know why it started (and does) this.

If the moderator wants to post this to the Hexhead area, please do so.

Thanks for any help.

Good evening, I had something similar in first and second gear and I think I cured it by changing all the stick coils. At least it has been fine for the last 2,500 miles.

My main reason for suspecting them, is because I figured after 178,000 miles they maybe due to having heat induced break done.

I should also mention I only use Chevron 94 octane fuel because it is the only one I have found without ethanol.

It's been happening for a long time, maybe2 years???? But like Basilr noted, it's really only noticeable during hard full throttle acceleration and only in the specific range of between 5 & 6K. I ride it hard keeping up with and in front of the sport bikes I ride with on Sundays. The bike is phenomenal, no complaints, power seems fine everywhere else as I mentioned. I run 89 octane, so bumping up to something higher would be an easy thing to try. I had it to Hermy's BMW for throttle sync and valve check. Valves did not need shimming, they synced the throttles. Bike still stumbled. When I changed the plugs it got a little better then when I put the K&N in it got a lot better (orig air filter was in 25K mi and dirty). Do you agree trying 90's octane would be the easiest thing to try next?

What a coincidence. My 2005RT does the same thing. Only on full, wide open throttle. First time I noticed it was on my first ride of the year.I went to pass a truck in 4th gear and at about 4500rpm, the bike jerked about 2 or 3 time like it was missing something. Only on wide open throttle. As long as I backed off a bit, it was fine.

 

I took it to the BMW dealer, whose mechanic I have full confidence in, and he replaced the plugs, swapped coils, adjusted the valves and TBS, balanced the temperature etc, etc, etc. I'm not sure he did anything with the FPC but did averything else he could think of. He and I both took the bike for a ride, and now it "stumbles" between 5-6000rpm. Not quite as badly (sometimes) but only on WOT. The only other thing he could think of was maybe a new wiring harness if it gets worse.

 

We just finished a 4 day trip and it didn't bother me but I didn't push it too much either. I may just live with it if nothing works but it sure would be nice to know why it started (and does) this.

 

If the moderator wants to post this to the Hexhead area, please do so.

 

Thanks for any help.

 

Sounds like the same Gremlin!!!!

It's been happening for a long time, maybe2 years???? But like Basilr noted, it's really only noticeable during hard full throttle acceleration and only in the specific range of between 5 & 6K. I ride it hard keeping up with and in front of the sport bikes I ride with on Sundays. The bike is phenomenal, no complaints, power seems fine everywhere else as I mentioned. I run 89 octane, so bumping up to something higher would be an easy thing to try. I had it to Hermy's BMW for throttle sync and valve check. Valves did not need shimming, they synced the throttles. Bike still stumbled. When I changed the plugs it got a little better then when I put the K&N in it got a lot better (orig air filter was in 25K mi and dirty). Do you agree trying 90's octane would be the easiest thing to try next?

Morning izquik

If it were my bike I would definitely try some 92/93 octane fuel as well as seeing how it runs out on a nice cool morning.

If the bike still acts up using 92/93 octane on a cool morning then you will probably need to look somewhere else (like upper stick coils, or FPC, or ????)

Next time that you visit your local BMW dealer see if they have any service bulletins on that 5/6k problem on the camhead bikes. BMW had some engine calibration issues/changes on the RT-P due to high speed operation so maybe that also effects the civilian bikes.

An update to this thread:

I was on a two week trip after having my BMW mechanic unsuccessfully try to get rid of my stumble.

I went to pass a vehicle in 4th gear. Two lane highway. Lost almost all acceleration facing oncoming traffic. Obviously missed a collision but it sure scared me.

I figured it had to have something to do with fuel supply. A friend I was visiting said his friend swore by Seafoam. I phoned the BMW dealer where my bike was serviced to set up another appointment as something HAD to be done. He said "Try Seafoam". So I did.

I put about 200ml into my 27 litre tank and the results were amazing. 80% correction to the problem. I left the next fill up alone, as recommended, and added another 200ml to the next (3rd) fill up.

The problem is now 99.9% gone. If I use my imagination, I may feel a burp in 4th and maybe in 6th but the difference is amazing.

My guess is that it was fouled fuel injectors that needed cleaning,and maybe any injector cleaner would work, but give Seafoam a chance.

Final and successful solution was two new upper stick coils plus,I had the fuel injectors cleaned.

Canadian price for coils was +/- $420 plus $150 for the injector cleaning, plus labour rate at my BMW dealer, but worth it to me.

I did a 240km ride home yesterday and the bike has never run better.