Looking for info on '04 K1200RS/GT Throttle System Operation

I've been trying to find information about how the throttle system operates on the K1200RS & GT bikes and have had no luck at all. So, does anyone know where this information may be available or are there any experts here that can explain the function of the throttle valve actuator and the throttle valve potentiometer and how they function in conjunction with the throttle cables.

Thanks

Ted

What year?


We ask that you always put the model and YEAR of the bike in question IN THE TITLE of any thread you start.

I don't think you can change the title after you post it, but if you include the year in your next post, I'll add it to your title.


(I added it after the post that follows this one).

Sorry about that. It's a 2004 GT.

Ted

I've never had to mess with mine, so I'm hardly an expert. But I'll tell you how I think it all works. Take it with a grain...

It is not a fly-by-wire system like most newer bikes. The throttle cable still moves the throttle linkage at the throttle body assemblies, which moves the butterflies. The computer needs to know how much fuel any given throttle position is asking for, so the throttle potentiometer gives it that feedback.

AFAIK, the actuator is used to fine tune the idle speed.

Thanks for the reply Jeff. I would think that your assessment is likely pretty accurate. I kind of suspected that the potentiometer would provide feedback for throttle position but really had no idea what the function of the actuator was.

Thanks again.

Ted

81664 said:

I've been trying to find information about how the throttle system operates on the K1200RS & GT bikes and have had no luck at all. So, does anyone know where this information may be available or are there any experts here that can explain the function of the throttle valve actuator and the throttle valve potentiometer and how they function in conjunction with the throttle cables.

Thanks

Ted

Click to expand...

What sort of problem are you trying to solve?

GREGFEELER said:

What sort of problem are you trying to solve?

Click to expand...

I am suspecting that I am not getting full throttle opening but didn't want to start making adjustments without understanding the function of the throttle valve potentiometer and throttle valve actuator.

Ted

81664 said:

I am suspecting that I am not getting full throttle opening but didn't want to start making adjustments without understanding the function of the throttle valve potentiometer and throttle valve actuator.

Ted

Click to expand...

You may have found this information already, but here is a document about the operation of the Throttle Valve Actuator.

81664 said:

I am suspecting that I am not getting full throttle opening but didn't want to start making adjustments without understanding the function of the throttle valve potentiometer and throttle valve actuator.

Ted

Click to expand...

Perhaps unrelated to your problem, but here's a link to a discussion about the TPS adjustment. I also found a number of articles referencing use of the GS-911 to perform the TPS adjustment.

https://www.bmwsporttouring.com/topic/67870-k12gt-throttle-valve-potentiometer/

GS-911:
https://www.gs911usa.com/

GREGFEELER said:

You may have found this information already, but here is a document about the operation of the Throttle Valve Actuator.

Click to expand...

Greg, Ted,

Since this older version of the PDF document about the Throttle-Valve-Actuator (TVA), I have done more tests and made a more recent version "1.4" of the same document. Additional info and minor corrections are noted at the end of the document (see attached PDF file).

OTHER NOTES: although I was very active on the old (now defunct) K1200RS dedicated web site/forum, I am visiting here only once in a while and saw this reply.

During last 10 years, I have done a lot of work on the TPS / TVA role on the K1200RS-GT-LT throttle-bodies. Much of this involves dismantling, testing and measuring using both GS911 and Voltmeter - so called reverse engineering because BMW and BOSH are providing very little info on these Motronic 2.4 system (as implemented on the K1200 "brick-engine" platform).

Based on these tests, I have also created another document to check TPS using either simple voltmeter OR GS911. Keep in mind that using GS911 is always better in case of intermittent / difficult problems because you can log "live data" of all EFI sensors into a file while the engine is running. This helps a lot to study the data after the fact - and may sometimes help do remote troubleshooting (although remote troubleshooting is always very tricky...).

View attachment BMW_K1200_Throttle-Valve-Actuator TVA (version 1-4).pdf

Greg and Jean,

Thank you both for providing those documents. Apparently my Google searching skills need some improvement. I will be spending some time studying these documents.

Thanks again

Ted

81664 said:

I am suspecting that I am not getting full throttle opening but didn't want to start making adjustments without understanding the function of the throttle valve potentiometer and throttle valve actuator.

Ted

Click to expand...

Would you mind describing some of your symptoms? Have you had your bike a long time? Did this start suddenly? Etc. Thanks.

81664 said:

Greg and Jean,

Thank you both for providing those documents. Apparently my Google searching skills need some improvement. I will be spending some time studying these documents.

Thanks again

Ted

Click to expand...

In my previous post, I had not included the latest PDF document specific to TPS for K1200 "brick-engine". See below for attached PDF file...

When reading / studying BOTH documents keep in mind the following:
1) you should NOT make any adjustemnt or change any parts before you fully understand what you are doing. In particular, I do not recommend touching the screws around the throttle-bodies having blue "tamper-proof" paint. Although I have done so myself for testing and finding the systen limitations, I certainly cannot garantee to solve any of these "messed-up" TB assy without being on-site. The BMW dealer will gladly sell you a TB assy properly set-up at the factory for $US$ 1292 (or $1421 with cruise-control) when things look very abnormal - this what they are trained to do if their diagnostic computer and a change of parts (TPS or TVA) cannot solve your problems.

2) When writing these 2 documents, I had to make certain assumptions about the reader - it was impossible to also include a course on how an EFI system works and what is the role of a TPS. The TVA of the K1200RS by itself is a bit unique - contrary to the very common TPS implemetation, an idle control system (when cold or warm) can be very different than this on other EFI systems (car or motorcycle).

3) to better understand the role of the TPS as implemented on Motronic 2.4 (most R1150xx and all K1200 "brick-engine") you also need to understand general principles of EFI systems using the so-called "Alpha-N" modeling. This is one of the most simple form of EFI on motorcycles. BOSCH designed Motronic 2.xx in the 1980s and perfected it late 1980 on some Euro cars. BWW choose a fairly simple EFI system for the K1200RS when it was initially designed around 1994-1996 (1st release in 1997 in Europe). Motronic 2.4 was more advanced than the old JETTRONIC of the K100-K75, but not very advanced compare to some EFI offered on other motorcycles brand of late 1990s.

4) later BMW models having 4 and 6 cylinders (slant-4 and slant-6 engines used on K1300S, K1300GT, K1600) and also starting on the R1200 boxer series in 2005, BMW is using a more complex EFI syetm that can track a lot more sensors and a lot more data than what we have on the older K1200RS.

I hope this helps...

GREGFEELER said:

Would you mind describing some of your symptoms? Have you had your bike a long time? Did this start suddenly? Etc. Thanks.

Click to expand...

I have only owned this bike for about 2 1/2 years. A few years ago I had a 1999 K1200RS. Since having this 2004 model it has always felt to me that it doesn't accelerate as hard at WOT as the 1999 bike did. A friend of mine has a 2002 K1200RS and a couple of weeks ago we were discussing this while in my garage. I asked him to compare the rotation of my throttle grip to his. His throttle grip rotates almost twice as far as mine (both bikes have cruise control). I don't know if this has anything to do with my perceived problem or not. I don't know if there was a design change between his 2002 model and my 2004 that would cause this. At this point I honestly don't know if I really have a problem or not (and haven't had much time to look into it). I just know that with some of these electronic fuel injection systems it's pretty easy to make things worse, so I just wanted to educate myself before digging into it.

Ted

81664 said:

I have only owned this bike for about 2 1/2 years. A few years ago I had a 1999 K1200RS. Since having this 2004 model it has always felt to me that it doesn't accelerate as hard at WOT as the 1999 bike did. A friend of mine has a 2002 K1200RS and a couple of weeks ago we were discussing this while in my garage. I asked him to compare the rotation of my throttle grip to his. His throttle grip rotates almost twice as far as mine (both bikes have cruise control). I don't know if this has anything to do with my perceived problem or not. I don't know if there was a design change between his 2002 model and my 2004 that would cause this. At this point I honestly don't know if I really have a problem or not (and haven't had much time to look into it). I just know that with some of these electronic fuel injection systems it's pretty easy to make things worse, so I just wanted to educate myself before digging into it.

Ted

Click to expand...

Although there has been at least 4 variation of the throttle-bodies on the K1200RS-GT "brick-engine" over the production of 1997-2005 (made by BING for BMW), none of these changes will affect the "normal" 86 degrees (+/- 2 degrees) total rotation at the handlebar grip.

With OR without the factory electronic cruise-control option, the throttle-bodies butterflies AND the end of the handlebar grip will have a 1-to-1 relationship AND you should see about 86 degrees rotation (+/-2 deg) Of course, with the electronic cruise-control option you see 2 throttle cables at the grip and at the throttle-bodies (instead of 1). With age and wear having 2 cables often leads to stiffer grip rotation (compare to non-cruise K1200RS).

See 2 attached photos: these were done with rubber grip removed to show the heated-grip wires rotation, but this is irrelevant - one can easily make a small mark at the end of his rubber grip and make the same check without removing anything.

Except for a major mess at the throttle-bodies linkage (broken , bent ??) OR a non-standard handle mechanism (below grip) , the only cause of a rotation restriction would be a bad re-assembly / alignment of either:
1) The upper 4 metal clamps holding the air-box intake tube to throttle-bodies
2) The lower 4 metal clamps between the throttle-bodies and the rubber lower stub for intake manifolds.

This install error has crop up occasionnaly on various K1200RS-LT forums after a major clutch OR rubber manifold change job. The one doing the job did not take note how the clamp were aligned when removed. FURTHERMORE, they comitted the sin not to check for mechanical interference at full throttle rotation before installing the fairings. See 2 more photos for recommend clamps alignment.

IMPORTANT: if you K1200RS/GT is equipped with the cruise-control, you might see different type of clamps for the frontal 2 cylinders above the Throttle-bodies. In most cases the factory has used special "flatter" clamp that does not have a screw mechanism - but instead need a special type of pliers to install. Their goal was exactly to avoid mechanical interferences with some part of the throttle-bodies at full rotation for these 2 frontal TB - the screw type clamps can still be installed (as shown) if one is very meticulous about position / alignment to avoid mechanical interference.

Given what you've added, I'd strongly recommend you not dig into your FIE system. Since the problem is at this point merely one of a hunch (?) I'd hate to see anything messed up with no real facts in play. And I hesitate to add, the sensation that one's throttle moves less than someone else's is way down the list of things I'd dig into if in fact a power loss was in play, which you're not yet even sure about.
I'd start with determining if there is even a problem at all. Do a roll-on with a similar bike? Put it on a dyno?

As good as the cables are on the Beemers, they do wear out.

Also, there is a plastic pipe inside heated throttle handles that can become a problem.

The throttle throw should be about 90 degrees. If you are not getting that, something in either the cables or the plastic pipe is giving you trouble.

I suggest you remove the throttle assembly, do some clean up and check that everything is moving correctly.

Note: On my 2002 K1200RS the air cleaner/intake muffler pulls off the throttle bodies, there are no clamps. Makes it very easy to observe the butterfly movement.

Another note: The two-cable throttle assembly can also be a gorilla to twist and keep at a steady opening. This is my third K1200RS and "they all did that."

I removed the return cable and disconnected one of the throttle return springs. This really loosened up the throttle, especially the closing.

To me the only down side is the cruise control kill switch in the return cable is not there. Not sure I ever used it anyhow.

A helpful website: https://www.realoem.com/bmw/enUS/select?product=M&archive=0

First of all, thank you to everyone who has responded. As I said earlier, I purchased this bike about 2 1/2 years ago specifically to make a project of it. The bike was in very nice condition and only had a little over 15K miles on it. I only rode it for about 300 miles before tearing it down to begin the "project". During that 300 miles I noticed the problem I described with what I perceived as a lack of full-throttle power as compared to my previous 1999 K1200RS. I just kind of ignored it as being all in my head and proceeded with the project. After completing the project and riding the bike for a couple thousand miles I finally decided maybe the problem wasn't just in my head after all and that's when I decided to look into it, but wanted to get a little more educated before making any changes. That's when I posted the inquiry here and I'm very glad I did. I've received some good advice and information. What really helped was the information from Jean about the 86 degrees of throttle rotation. I checked mine and determined that I was getting about 35 degrees of rotation. So, I pulled the left side fairing panel and inspected the clamps on the rubber throttle body connectors as Jean suggested and sure enough, the clamp screw on the #3 TB connector was interfering with the adjustment screw on the TB shaft. Loosened and rotated the clamp about 1/8" and all is good now.

Thanks again for all the help

Ted

81664 said:

First of all, thank you to everyone who has responded. As I said earlier, I purchased this bike about 2 1/2 years ago specifically to make a project of it. The bike was in very nice condition and only had a little over 15K miles on it. I only rode it for about 300 miles before tearing it down to begin the "project". During that 300 miles I noticed the problem I described with what I perceived as a lack of full-throttle power as compared to my previous 1999 K1200RS. I just kind of ignored it as being all in my head and proceeded with the project. After completing the project and riding the bike for a couple thousand miles I finally decided maybe the problem wasn't just in my head after all and that's when I decided to look into it, but wanted to get a little more educated before making any changes. That's when I posted the inquiry here and I'm very glad I did. I've received some good advice and information. What really helped was the information from Jean about the 86 degrees of throttle rotation. I checked mine and determined that I was getting about 35 degrees of rotation. So, I pulled the left side fairing panel and inspected the clamps on the rubber throttle body connectors as Jean suggested and sure enough, the clamp screw on the #3 TB connector was interfering with the adjustment screw on the TB shaft. Loosened and rotated the clamp about 1/8" and all is good now.

Thanks again for all the help

Ted

Click to expand...

First, congratulations on the quick and easy fix to a major problem. Secondly, any idea how the clamp got mis-positioned? Did I mess part of this thread?

GREGFEELER said:

First, congratulations on the quick and easy fix to a major problem. Secondly, any idea how the clamp got mis-positioned? Did I mess part of this thread?

Click to expand...

Greg,

Since I actually noticed this issue when I first bought the bike, I'm just guessing that maybe it was mis-positioned during a service that was done while the previous owner had the bike. Could have been that the clamp was loose and someone positioned it for easy access to the clamp screw and tightened it. Just a WAG on my part. I'm just glad it was an easy fix.

Ted