1150 GS running on one cylinder

[Markst1]

Hello,
I have a problem. Went out to the garage to start my GS just to hear the engine run. It has been put up in the garage for the long, cold, white Cleveland winter. I haven't been totally neglecting it, however. A few weeks ago I installed a set of PIAA's with autoswitch (works fine). I didn't think to start the bike after the light project.
So when I went to start it today, it only ran on the left cylinder. I was a bit puzzled. I remembered that it sometimes started bit rough in the fall when it was cold, before being put up (but nothing like now). It was due for a spark plug change and I had a set in my tool box so I changed them out with no improvement.
So, any ideas of what could be wrong? I lifted the tank (not completely off, just jacked up the rear) during the light project. Maybe I loosened an important connection? Maybe the spark plug wire to the right cylinder?
I am a bit intimidated by the complexity of this bike. I m very used to and comfortable with my more simple /6, and I am relatively unfamiliar with the oilhead.
By the way, in quest to hear the boxer song, I gave the R75/6 a go. It jumped to life after about 3 sec, and purred like a kitten. Ahhhh.

Any ideas appreciated.

Theo Marks

'74 R75/6
'01 R1150GS

[PGlaves]

Check the throttle cable on the right side. I think that you probably dislodged the end of the cable sheath from the adjuster ferrule when you did the wiring. This is a common occurance.

[riderR1150GSAdv]

What Paul said! However, if it started acting up before the winter, some connections may have corroded some (more) and are now preventing the motor from running right.
If you undid a connection under the tank than you have to back and check them all.
Just take your time going around checking them. It may be a simple problem.
The bike isn't all that complicated. Heck compared to an LT(had one :heart ) the GS is like in the stone age :stick :D :D

[Boxerkuh]

Since you are in the deep winter, here maybe another benefit for motification. Install some quick release fuel lines. That will enable you to remove the tank much faster. Once the tank is off, you will be able to inspect your work much better. Check the plugs, check the injectors and all the connections. While you have the tank off you can clean up under there, check all the electrical connections. I did this on an annual basis and was always amazed how much dirt and bugs found there way in (I had a 99 RT). Take your time. :thumb It will probably be something very simple :doh

[kenk]

Check the throttle cable on the right side. I think that you probably dislodged the end of the cable sheath from the adjuster ferrule when you did the wiring. This is a common occurance.


Take Pauls advice. By lifting the tank, the crossover cable to the right throttle body can pop out of the seat just above the adjustment point. I've done this several times.

[pmdave]

The spark plug caps have resistors in them. If the resistor starts to burn out, the indication is the engine running on one cylinder at idle. If the resistor burns out entirely, the plug won't fire on that side, or it may kick in only at faster RPMs.

I'm slightly suspicious of the resistor because you observed some problems when it was last running.

You could also have a clogged injector on that side. Do you make a practice of changing the fuel filter regularly? Do you use gas stabilizer in your fuel when laying up for the winter?

pmdave

[kenk]

The spark plug caps have resistors in them. If the resistor starts to burn out, the indication is the engine running on one cylinder at idle. If the resistor burns out entirely, the plug won't fire on that side, or it may kick in only at faster RPMs.

I'm slightly suspicious of the resistor because you observed some problems when it was last running.

You could also have a clogged injector on that side. Do you make a practice of changing the fuel filter regularly? Do you use gas stabilizer in your fuel when laying up for the winter?

pmdave

I think the problem is as simple as lifting the tank, pulling the crossover cable out of its seat. Again...I've done this several times and the bike runs like its only on one cylinder afterwards. Reseat the crossover cable into its bucket on top of the right throttle body and the problems fixed.

[Markst1]

Thanks to all who have offered up great ideas and experiences,

I haven't been able to fully explore this yet, but I expect to get to it this weekend.
I don't think that it is the throttle cable, because both throttle bodies seem to be opening and closing together. I have a few questions, as I have not really had any experience working on this bike much (it's relatively new to me):

Do I need to totally pull the tank, as in disconnect the hoses, to get access to the wiring underneath it? Or can it be slid back far enough after removing the right side bolt?

I think I saw a good reference for changing the hoses to a quick release system, but can't remember where. Any suggestions on the best way to make this mod?

I am used to testing the spark by laying the plug on the cylinder. Can this be safely and easily done with this bike. I understand that the motor has paint on the outside. Will this conduct electricity?

Thanks in advance

Theo Marks

'74 r75/6
'01 r1150GS

[Markst1]

:) You guys are all so smart. Like so many suggested, it was the throttle cable. While I was at it, I pulled the tank back to check out the electronics up front. I'm starting to get familiar and comfortable wrenching this high-tech machine (compared to my /6). I'm getting warmed up for the valve adjust, throttle body synch, fluid changes, and alternator belt before spring riding season. I think that with patience on my part and generous help from all of the knowledgeable and experienced folks on this site I'll be alright.
Thanks again

Theo Marks

'74 R75/6
'01 R1150GS

[kenk]

:) You guys are all so smart. Like so many suggested, it was the throttle cable. While I was at it, I pulled the tank back to check out the electronics up front. I'm starting to get familiar and comfortable wrenching this high-tech machine (compared to my /6). I'm getting warmed up for the valve adjust, throttle body synch, fluid changes, and alternator belt before spring riding season. I think that with patience on my part and generous help from all of the knowledgeable and experienced folks on this site I'll be alright.
Thanks again

Theo Marks

'74 R75/6
'01 R1150GS

Theo,

Common mistake we all make on oilheads. Recommend after reseating checking the throttle body synchronization with a TwinMax or other synch devices. Synchronization is very sensitive on an oilhead and a proper synchronization will make a big change with vibration on an oilhead. Recommend referring to the excellent article in BMW Owners News a few months back on how to use a TwinMax. Excellent product for the cost of one BMW Service hour. It will pay for itself in one use.

[Markst1]

Kenk (and all)
Thanks for the advice and encouragement. I do have a twinmax, but haven't used it on the GS yet. The article that you referenced looks comprehensive. Like I said, I plan the valve adjust followed by TB synch soon.
I still don't understand how the throttle cables work. Does the cable from the handlebar work the left TB and the right is slaved off of the left? Or are the two cables that I see at the TB's each driven off of the handlebar control? It's hard to see where these cables come from and how they are hooked together (somewhere in front of and/or below the battery).
Thanks
Theo Marks

'74 R75/6
'01 R1150GS

[bmwmick]

Theo,
This will give you a pretty good idea of how your cables are routed:
http://tinyurl.com/9rm5o
Enter the last 7 digits of your VIN to see the online ETK.
http://www.realoem.com/bmw/select.do?vin=&kind=M&arch=0