Cold Idle adjustment trouble

[Deleted account 210214001]

I did a valve adjustment and TB synch ('02 1150GS-Adv with 52k miles). Now I can't get my cold idle cable adjusted right. Prior to the work, the cold idle did what it is supposed to do, namely, at the first detent it raised the idle about 800-ish rpm and at the "hold it there" position raised the idle even more although I don't remember by how much.

I did the TB synch as usual (I've done these quite a bit in the past, it's been a few years since I had an 1150 now, though.)
set the adjuster gap on the cold idle and throttle to about 1mm
proceed with the TB synch starting with 2mm slack at the TBs
set the throttle to 0.5mm slack
set the cold idle to 0 slack...or at least try to...
The adjuster on the cold idle is out as far as it can go and I get an increase in idle only at the "hold it there position" and even that's a slight increase. Prior to the TB synch, the cold idle adjuster was out pretty far, too. For what it's worth, with the throttle set to 0.5mm slack, I get nearly instantaneous movement from the TBs when I twist the throttle.

I'm going to go over everything again just short of actually re-synching. In the meantime does anyone have any ideas? Am I missing something fundamental? Are the cables just so gone that I need to replace?

Thanks,
Bohdan

 

[oneeleven]

Sounds like too much free play in your cables at the throttle bodies.

 

[beemer pimp]

Yeah same here, just couldn't be arsed fixing anyway according to manual bike shouldn't idle , star and ride.

 

[Deleted account 210214001]

Thanks, guys. I know others have had similar problems with their cold idle and got the same suggestion, but I couldn't wrap my head around why I could get instantaneous movement from the TBs when I move the throttle while having slack in the lower cables. I was mowing the lawn and thinking about how the Bowden box works. I think I figured it out. Bear with my nerdiness for a moment...

If there's slack in the lower cables but I have the throttle slack set to zero, I will, indeed get instantaneous movement of the TBs. What I did by setting the throttle slack to zero is I took up the extra slack in the lower cables by partially rotating the Bowden box. Therefore, I'm essentially adding slack to the cold idle cable and it is even more slack than before. There's not enough adjustment at the cold idle to take out all the "extra" slack I created.

What I need to do -- as you suggest, oneeleven -- is to take out the excess slack in the lower cables so that there's almost tension on the Bowden box. Then, when I set the throttle slack, I'm affecting only the throttle cable and not the Bowden box. Barring a grossly stretched cable, that leaves me with ample adjustment to get the cold idle slack set to zero.

How'd I do?

Bohdan

 

[Deleted account 210214001]

Fixed!

Thanks guys! Not 10 minutes after I posted "how I think this works," I went out and re-did the adjustments and TB synch. Now, idle is around 1,100 rpm, first detent on the cold idle bumps it to 2,700 rpm or so, "hold it there" stabilizes somewhere round 3,500-3,700 rpm.

I love figuring out stuff like this and then applying it.

Bohdan

 

[beemer pimp]

Savage so what was the problem ?

 

[Cook1e]

Post #16 on this thread...

http://www.ukgser.com/forums/showthread.php/359950-R1150GS-quot-choke-quot-not-working

 

[Deleted account 210214001]

Post #16 on this thread...

http://www.ukgser.com/forums/showthread.php/359950-R1150GS-quot-choke-quot-not-working

Yeah, that's about right. I did the adjustments per the manual but my error was in not removing enough slack from the throttle body cables.

The idle speeds I posted above were starting with a warm engine (4-5 bars), not from cold. I didn't specify that. The point of it is that I've got the cold idle cable adjusted to zero slack and that I get a nice rise in the idle when I pull it to the first detent and a bigger rise when I pull it to the high hold. For the sake of closure I'll update this thread when I go check idle speeds from cold.

Bohdan

 

[beemer pimp]

Post #16 on this thread...

http://www.ukgser.com/forums/showthread.php/359950-R1150GS-quot-choke-quot-not-working

Ah to much effort on RT , maybe on next service......

 

[King Rat]

Thanks guys! Not 10 minutes after I posted "how I think this works," I went out and re-did the adjustments and TB synch. Now, idle is around 1,100 rpm, first detent on the cold idle bumps it to 2,700 rpm or so, "hold it there" stabilizes somewhere round 3,500-3,700 rpm.

I love figuring out stuff like this and then applying it.

Bohdan

Sounds very fast idle, on all counts....

 

[Roger 04 RT]

Liked the book procedure link above. Last month I copied the full procedure with notes into this post: http://forums.bmwmoa.org/showthread...stment-Beyond-Zero-Zero&p=1003851#post1003851.

I had to shim the handle bar end of the adjuster but also back off the final tensioning to reduce cold RPM to 2500. TPS reading on the GS-911 is now 3.5 degrees in the mid detent position.

 

[Deleted account 210214001]

Sounds very fast idle, on all counts....

The idle speeds I posted above were starting with a warm engine (4-5 bars), not from cold. I didn't specify that.

1100 rpm is right about on spec for idle (1050+/-50 is what my documentation shows). As I stated earlier, the increased idle numbers I reported were for a warm engine. They should fall lower when I try on a cold engine.

 

[Deleted account 210214001]

I had to shim the handle bar end of the adjuster but also back off the final tensioning to reduce cold RPM to 2500.

And I'll end up doing the same if the numbers still are too high on the cold engine. Thanks for the reminders and tips, everyone!

 

[King Rat]

That nice Mr. Steptoe gets mine to idle at around 800rpm, for minutes on end when warm and 1000rpm when cold on first click of the thumb bar - I don't need the full lift to get started. I haven't set it up mind, my mechanical skills amount to putting petrol in the top, air in the bottom and oil in the middle. I reckon it is cheaper to have it done by someone who knows than muck it up myself and cause expensive damage. Neil has a phrase for people like me......"step away from the tollbox"

I am not advocating you do the same, merely pointing out what my bike does. It doesn't stem from a knowledgeable standpoint, just an observatory one. I admire you for taking the problem on.

 

[Deleted account 210214001]

No explanation needed. I'm sorry if I came across as harsh. What you describe: about 800rpm is what I get when the engine is cold, too! That's where the cold idle cable comes into play, raising the tickover to some level where it runs smooth. Warm idle for me is at 1050-1100, sometimes a bit lower. If it goes too much lower, it gets very lumpy.

And let it be known that I would be hard-pressed to question Neil on any GS matters!

 

[beemer pimp]

Yeah 1000-1100 rpm is spot on

 

[Deleted account 210214001]

Reporting back...

Reporting back after a cold-engine start. Idle with no cold-idle lever is about 800-850 rpm. With cold-idle lever at the detent, about 1100 rpm. At high-hold, idle is about 1700 rpm. In other words, all where it should be and I didn't need to back off the adjuster.