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#999142 - 10/17/17 12:19 PM Possible way to adjust messed up TB stop screws  
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Hello everyone. This is my first post on this forum and I want to share some findings for adjusting throttle body stop screws on camhead. This is work in progress so I'm not 100% positive whether it will work for everyone. I have done it on one bike only, so not enough statistics.

I strongly oppose to even touch the stop screws, even on older models (referring to zero to zero procedure). Yes you can do it, but you can mess other things in ECU fueling maps. Not to mention that by this process you are artificially correcting something and by doing that you can mask some other issues with the bike.

I worked on my friends R1200GS ADV Camhead 2010. He both it as used bike with little to none service history. After difficulties with TB sync I have noticed that someone has been playing with the stop screws and the differential vacuum at idle was outside of specified 25mbar values. Of course the reason for this can be something else, but after checking everything else I dared to adjust the stop screws. So here it goes:

Preconditions: Fully functional and clean throttle bodies, injectors, idle stepper motors, TPS, oxygen probes, exhaust flap, fuel pump, fuel pump controller, fuel pressure regulator, fuel hoses etc. Correctly adjusted valves, clean air filter, no air leaks, no blockage in air paths

Tools needed: Precise TB sync tool which can measure small differential vacuum. Diagnostic tool like GS-911 or some other BMW diagnostic tool.

The theory in mind was to adjust the stop screws without moving the TPS. Target was to adjust them so the differential vacuum is within spec and at the same time O2 sensors reading Lambda = 1

Step by step procedure:

1. Reset adaptation values and without touching the throttle let the bike idle until reaching operating temperature. Four bars on temp gauge or minimum 60 degrees Celsius. Switch off the ignition and wait for about 5 minutes

2. Switch on ignition and calibrate exhaust flap and idle stepper motors then switch off ignition

3. TPS reset

- with ignition off, open the throttle twist grip to wide open position and while holding it there turn on ignition and wait 15 seconds

- while still holding the throttle open, turn off ignition and wait for another 15 seconds before letting go the throttle

- turn on ignition and wait for another 15 seconds then turn off ignition

4. Fixing TPS in position. With the ignition off disconnect the connector from the TPS. Measure the resistance between middle and right pin on the TPS and write down the value. Remove the TPS from the throttle body and fix the TPS to the same value measured before. This can be tricky since the TPS is very sensitive and very easy to move. I used play dough to do this :-). Connect the TPS connector and just let the TPS to hang.

5. Slacken the throttle cables on both TB and let a lot off play so they can not interfere with stop screws adjustment

6. Loosen the stop screws and turn the fixing nut far from the butterfly point so you have enough thread for adjusting

7. Connect the TB sync tool as usual

8. Connect the diagnostic tool and start the bike. Monitor the engine temperature and O2 sensor values. After reaching engine temperature over 60 degrees Celsius, start adjusting the stop screws side to side until reaching near Lambda = 1 on both O2 sensors. At the same time follow the TB sync tool to confirm that both TBs are in sync and within specified 25 mbar differential vacuum with left cylinder leading slightly. This is very tricky because there is limited access to the stop screws and you don't want to overheat the engine. Best to have some cooling fans. The most tricky part is fixing the stop screws. Even slight movement can make difference.

9. After fixing the stop screws, turn ignition off and screw the TPS back on the TB.

10. Do a TPS reset as described in step 3.

10. Adjust the TB cables and go through regular TB sync procedure.

As I wrote earlier this is work in progress. While I was adjusting the stop screws I was also following the idle stepper motor openings. What is not clear to me is what would be the target for Lambda factor on O2 probes and idle stepper openings. I did not have any previous data from working bike to compare. Before I started the stop screws adjustment, Lambda factor was 0.85 which is rich mixture and I could smell that from the exhaust so decided to reach Lambda = 1. Ended with Lambda = 1 and idle stepper motor opening of 20% at operating temperature.

Maybe someone have also worked on this issue and we can compare some data for Lambda parameters and idle stepper motors on issue free bike. Maybe roger 04 rt can help here with his findings and experience.

#999147 - 10/17/17 01:25 PM Re: Possible way to adjust messed up TB stop screws [Re: 14TLC]  
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Morning 14TLC

I guess I'm really missing something here or you left some things out of your procedure?

Using lambda to set idle screws seems fruitless as the lambda is self correcting by the fueling computer so you are sort of chasing a ghost.

I see no mention of holding the idle steppers at a fixed value during the screw adjustment so you (we) have no idea on how much of your base screw setting is being cancelled out or added to by the computer controlled stepper pintle position.

What WAS the original stepper count (position) before messing with the base idle screws? What is the present hot engine idle stepper counts (position) after a nice long ride then drop to curb idle. What is the cross side stepper count delta at hot engine idle? What WAS the stepper count delta at hot engine idle with the >25mbar reading?

Are BOTH side throttle cams now lifting off their base idle stop screws at EXACTLY the same time as the twist grip is turned? (this is a very important observation)

Your TPS re-learn procedure seems strange, I haven't seen that in any of the BMW 1200 manuals that I have? (on the BMW 1200 bikes that do use a TPS re-learn it has always been a key-on full throttle sweep from closed to full open)

Last edited by dirtrider; 10/17/17 01:30 PM.

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#999176 - 10/17/17 11:52 PM Re: Possible way to adjust messed up TB stop screws [Re: 14TLC]  
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Hello dirtrider,

Everything that you have pointed out actually crossed my mind in different stages of the process. I was also surprised about the lambda factor behavior. I will explain what was actually happening so you have better picture. This was my first time doing this so I maybe I left out some essential steps in the process. Wanted to share this so I can hear opinions and experiences.

The bike had very erratic idle and often stalls. First thing was faulty TPS at near idle position. Almost every time after releasing the throttle it will land with different values. There was improvement after changing the TPS, but the engine was off balance. During the TB sync I have noticed that the throttle stop screws were messed. Broken paint marks and obvious scratch from screwdriver.

The diagnostics that a was using did not have data logging and graphing of live data for further analasis. It also not have feature to manually lock the idle stepper motors and at the same time watching other parameters like temp, idle steppers position. injection period and lambda factor. It was quite difficult to track changes in values just looking the numbers while the engine had erratic idle and stalls. So I installed some desktop screen recording software to record the changes which unfortunately ended with corrupted video file. If I remember correctly the right cylinder was pulling more vacuum and had about 0.1 lambda factor grater then the left cylinder. Maybe 0.92 over 0.82, but not sure. I don't remember the position of stepper motors.

Because I could not lock the steppers I started adjusting the stop screw like described in previous post with stepper motors on. What was interesting is that lambda factor fluctuates around present value with +/- 0.05. I turned the right stop screw to match the lambda of the left cylinder and stabilize the erratic idle behavior. From that point on I started adjusting both stop screws little by little. When turning the screws, lambda factor was in fact changing and it will stay in position when not turning the screws. There was little +/- fluctuation as temperature raised, but not significant change as that when turning the stop screws All this with TPS removed from the TB and fixed in position. While lambda factor was rising the stepper position was dropping in % to compensate. The representation of stepper position was in %. Starting from 100% with engine not running, about 85% after cold start and it will drop as the engine temperature rises. After the adjustment I ended with Lambda factor fluctuating around 1 on both cylinders and steppers with position around 20% on both cylinders. While doing this I was also watching the TB sync tool which ended with around 6 to 8 mbar differential vacuum.

I don't really know if these values are the target. I'm also a little bit skeptic, especially for the stepper position which I think with 20% left , much of the adaptation range has been used. That is why I'm asking if someone have these values from another bike. Positions of the steppers, lambda, injection period related to the engine temperature.

Related to the butterfly valves, I'm pretty sure they start raising at the same time. This is controlled by the cables after proper cable adjustment if you referring to that.

Do you have any experience in adjusting stop screws on camhead or hexahead models with stepper motors. I have not come across any solution posted on internet.

Referring to the TPS reset, I have seen that procedure at a dealer after software upgrade of one R1200GS camhead. There was no specific command to start this procedure but the diagnostic software itself instructed this. I think it was called something like manual stepper calibration, but the technician said that it was TPS teaching procedure. There was no instruction how much time to wait but the software itself was telling when to hold and release the throttle and when to switch on/off ignition, but time intervals were 10-15 seconds. Also here http://www.rexxer.com/fckimages/BMW-TPS-Reset-PDF.pdf

Last edited by 14TLC; 10/18/17 12:00 AM.
#999202 - 10/18/17 12:43 PM Re: Possible way to adjust messed up TB stop screws [Re: 14TLC]  
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It seems you could turn the key off, then to on allowing the steppers to reset then unplug them. They should be even at every key on.

Then adjust the vacuum to match both sides ignoring everything else.

This is after making sure valve adjustment in in spec.

Correct me if I am wrong.

David


'76 R75/6 67,000 miles
2000 R1100RT 137,000 miles. (retired)
11 Versys 11,000 miles
12 R1200R!
#999203 - 10/18/17 01:11 PM Re: Possible way to adjust messed up TB stop screws [Re: David R]  
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Originally Posted by David R
It seems you could turn the key off, then to on allowing the steppers to reset then unplug them. They should be even at every key on.

Then adjust the vacuum to match both sides ignoring everything else.

This is after making sure valve adjustment in in spec.

Correct me if I am wrong.

David

If it was so simple :-) When steppers are disconnected, the BMSK will run with predetermined fueling map and making the adjustment useless when connected again. You can adjust matching vacuum at any TB butterfly position. But which is the correct one that will allow specified air volume with range for steppers for correction.

Disconnected and parked steppers are different things altogether.

#999204 - 10/18/17 01:13 PM Re: Possible way to adjust messed up TB stop screws [Re: David R]  
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Originally Posted by David R
It seems you could turn the key off, then to on allowing the steppers to reset then unplug them. They should be even at every key on.

Then adjust the vacuum to match both sides ignoring everything else.

This is after making sure valve adjustment in in spec.

Correct me if I am wrong.



Morning David

You have the basic idea but it won't work that easy. Depending on engine temp the steppers won't do a key-on reset to curb idle counts but will reset to engine starting counts which are well above the basic hot engine curb idle counts.

If a person could fool around with the idle RPM & get each stepper to settle in at the required hot engine idle count, THEN, disconnect each stepper at that exact count then your method should work. (or at least be a good basis for a baseline to start from then match the actual running counts vs curb idle vacuum delta vs throttle plate initial lift point


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#999206 - 10/18/17 01:21 PM Re: Possible way to adjust messed up TB stop screws [Re: 14TLC]  
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Originally Posted by David

If it was so simple :-) When steppers are disconnected, the BMSK will run with predetermined fueling map and making the adjustment useless when connected again. You can adjust matching vacuum at any TB butterfly position. But which is the correct one that will allow specified air volume with range for steppers for correction.

Disconnected and parked steppers are different things altogether.


Morning David

I don't believe this to be true--- On the BMW 1200 the steppers are 4 wire steppers so there is NO direct feedback of stepper position or operation to the BMS-K. Therefore it should still run in closed loop with dynamic fueling correction even with the steppers disconnected.


D.R. ___
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#999207 - 10/18/17 01:23 PM Re: Possible way to adjust messed up TB stop screws [Re: 14TLC]  
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@ dirtrider

Do you know what is the count range of the steppers as per GS-911 so I can relate with percentage readings that I have.

#999209 - 10/18/17 01:35 PM Re: Possible way to adjust messed up TB stop screws [Re: 14TLC]  
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Originally Posted by 14TLC
@ dirtrider

Do you know what is the count range of the steppers as per GS-911 so I can relate with percentage readings that I have.


Morning 14TLC

Lots of variables on this one as it depends on engine oil viscosity, altitude, air density, alternator loading, alcohol content in the fuel, transmission gear oil thickness (if running in neutral with clutch engaged), miles on engine, engine compression, etc.

I do have some trapped 1200 camhead idle count data (possibly with altitude numbers) but I am not near that data at the moment as it is on my shop computer.


D.R. ___
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#999210 - 10/18/17 01:43 PM Re: Possible way to adjust messed up TB stop screws [Re: dirtrider]  
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Originally Posted by dirtrider
Originally Posted by 14TLC
@ dirtrider

Do you know what is the count range of the steppers as per GS-911 so I can relate with percentage readings that I have.


Morning 14TLC

Lots of variables on this one as it depends on engine oil viscosity, altitude, air density, alternator loading, alcohol content in the fuel, transmission gear oil thickness (if running in neutral with clutch engaged), miles on engine, engine compression, etc.

I do have some trapped 1200 camhead idle count data (possibly with altitude numbers) but I am not near that data at the moment as it is on my shop computer.






Thanks. This would help for better understanding.
I was also referring to the complete range as steps end to end positions. To make relation for example 100 counts in GS-911 to percentage in my readings.

#999212 - 10/18/17 01:48 PM Re: Possible way to adjust messed up TB stop screws [Re: dirtrider]  
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Originally Posted by dirtrider
Originally Posted by David

If it was so simple :-) When steppers are disconnected, the BMSK will run with predetermined fueling map and making the adjustment useless when connected again. You can adjust matching vacuum at any TB butterfly position. But which is the correct one that will allow specified air volume with range for steppers for correction.

Disconnected and parked steppers are different things altogether.


Morning David

I don't believe this to be true--- On the BMW 1200 the steppers are 4 wire steppers so there is NO direct feedback of stepper position or operation to the BMS-K. Therefore it should still run in closed loop with dynamic fueling correction even with the steppers disconnected.


What I have noticed is that with steppers disconnected the lambda correction factor reading got fixed value of 1.0...... and not changing.

What do you mean with "NO direct feedback"

#999215 - 10/18/17 02:03 PM Re: Possible way to adjust messed up TB stop screws [Re: 14TLC]  
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Morning 14TLC

I still can't confirm that TPS re-learn procedure that you at using (doesn't seem to be a reasonable way to re-set/re-teach a TPS & I sure don't show it in any of my BMW service bulletins. (are you sure this wasn't used on a fly-by-wire electronic throttle control bike? )

In any case I haven't had to do a curb idle screw (best hope resetting) on the BMW camhead.

I have done 2 BMW hexheads & a few BMW 1150 bikes. The 1150 (non stepper) bikes are easy to get back close to where they should be as there isn't that darn stepper control to confound the setting issue.

On one 1200 hexhead I was able to match the blue indexing paint up on one side then simply matched the other side using the known good side as a qualifier (this one worked out great & I had total confidence in the setting being close to factory base air flow)

The other hexhead was a pest to work with as the blue indexing paint was totally gone. The saving thing on this one was I had a very similar 1200 bike (my own) to run at the same time to compare stepper counts & throttle follower action.

I started out with both side curb idle screws set identically at EXACTLY 1/2 turn in from a fully closed (verified closed) throttle plate (that gave me a known & fairly even starting point & actually gave fairly close stepper counts at initial hot engine idle curb idle)

Once I got the hot engine stepper count (& cross side idle vacuum delta) fairly close I then ran the engine RPM up to just above the stepper link up & set the mid throttle cross side balance. (this is the important setting & the one that you ride around in the most)

I then cleared all the BMS adaptives then tweaked they base curb idle screws to get the hot engine, closed loop stepper count to be close to the known good bike (didn't take much).

I then shut engine down then checked BOTH SIDE initial TB throttle cam lift off the base idle screws (it was off just slightly) so I went back through it again using the existing base idle screw settings as a starting point (very little changes).

I'm not sure if I got it back to the initial factory/vendor) base screw setting but the bike ran good, idled good, started good, didn't die at dropped throttle after a long hiway run & seemed to have a stable curb idle (the owner says it still runs great).


D.R. ___
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#999221 - 10/18/17 02:21 PM Re: Possible way to adjust messed up TB stop screws [Re: 14TLC]  
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Originally Posted by 14TLC


What I have noticed is that with steppers disconnected the lambda correction factor reading got fixed value of 1.0...... and not changing.

What do you mean with "NO direct feedback"


Morning 14TLC

With a 4 wire stepper (2 wires high & 2 wires low) the fueling computer has no idea where the stepper count REALLY is as the steppers have no way of reporting their position back to the fueling computer. (there is no position feedback circuit back to the fueling computer)

At initial (pre start) key-on the fueling computer commands both steppers to home (completely closed pintals) then assigns that position as "0" counts. From then on (on this run cycle) the fueling computer only knows where the steppers are by how many counts it has commanded each to move.

So basically if-- the computer starts out with a 100 count command then commands a 3 count extend it knows the stepper count should be at 97 counts it then commands another 2 count extend it now knows the counts should be at 95 counts (the computer ONLY knows where it starts & where each command puts it) so if a stepper loses a count or slips a thread the computer doesn't know the stepper pintles exact position it only knows the pintles COMMANDED position.


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#999223 - 10/18/17 02:27 PM Re: Possible way to adjust messed up TB stop screws [Re: dirtrider]  
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Originally Posted by 14TLC
What I have noticed is that with steppers disconnected the lambda correction factor reading got fixed value of 1.0...... and not changing.


Morning 14TLC

I'm not sure on this one but could be as simple as-- with the steppers disconnected the base air flow remains extremely constant so the o2 sensors can then easily hold closed loop fueling constant.


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#999249 - 10/18/17 09:11 PM Re: Possible way to adjust messed up TB stop screws [Re: dirtrider]  
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Originally Posted by dirtrider
Originally Posted by 14TLC
What I have noticed is that with steppers disconnected the lambda correction factor reading got fixed value of 1.0...... and not changing.


Morning 14TLC

I'm not sure on this one but could be as simple as-- with the steppers disconnected the base air flow remains extremely constant so the o2 sensors can then easily hold closed loop fueling constant.



Could be. But even if it is like that, the injection period should vary as engine and air temperature raises, thus varying the fuel quantity. The fuel itself caries oxygen so there should be slight variation. I will double check this when bike comes over again for week or two. Just to be sure and understand what BMSK is doing in this state.

#999251 - 10/18/17 09:16 PM Re: Possible way to adjust messed up TB stop screws [Re: 14TLC]  
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Originally Posted by 14TLC

Could be. But even if it is like that, the injection period should vary as engine and air temperature raises, thus varying the fuel quantity. The fuel itself caries oxygen so there should be slight variation. I will double check this when bike comes over again for week or two. Just to be sure and understand what BMSK is doing in this state.


Evening 14TLC

With the steppers disconnected just pull a vacuum plug (or evap hose) off the bottom of a TB then see what you get.


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#999276 - 10/19/17 09:14 AM Re: Possible way to adjust messed up TB stop screws [Re: dirtrider]  
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Originally Posted by dirtrider


The other hexhead was a pest to work with as the blue indexing paint was totally gone. The saving thing on this one was I had a very similar 1200 bike (my own) to run at the same time to compare stepper counts & throttle follower action.

I started out with both side curb idle screws set identically at EXACTLY 1/2 turn in from a fully closed (verified closed) throttle plate (that gave me a known & fairly even starting point & actually gave fairly close stepper counts at initial hot engine idle curb idle)

Once I got the hot engine stepper count (& cross side idle vacuum delta) fairly close I then ran the engine RPM up to just above the stepper link up & set the mid throttle cross side balance. (this is the important setting & the one that you ride around in the most)

I then cleared all the BMS adaptives then tweaked they base curb idle screws to get the hot engine, closed loop stepper count to be close to the known good bike (didn't take much).

I then shut engine down then checked BOTH SIDE initial TB throttle cam lift off the base idle screws (it was off just slightly) so I went back through it again using the existing base idle screw settings as a starting point (very little changes).

I'm not sure if I got it back to the initial factory/vendor) base screw setting but the bike ran good, idled good, started good, didn't die at dropped throttle after a long hiway run & seemed to have a stable curb idle (the owner says it still runs great).



Do you know what actually is the difference in idle control between hexhead and camhead? It seems to me that the same procedure can work on the camhead also.

You did not mention anything about the TPS in this process. Did you have to relearn it at some point?

How do you actually verify fully closed throttle plate?

RPM up to just above the stepper link up By this you meant the point when the idle control is no longer in play?

How can you check whether initial TB throttle cam lift starts at same time? I can recognize when they reach back to the stop screws at same time, but lift at the same time? By verifying with the TB sync tool?


Sorry if I bother you with so much questions, but I'm pleased to finally discuss with someone who have been working on this challenging task and have something meaningful to say

#999277 - 10/19/17 11:06 AM Re: Possible way to adjust messed up TB stop screws [Re: 14TLC]  
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Morning 14TLC


Do you know what actually is the difference in idle control between hexhead and camhead? It seems to me that the same procedure can work on the camhead also.--No, I don't know ALL the differences, they are definitely close but I haven't ever compared them item for item.

You did not mention anything about the TPS in this process. Did you have to relearn it at some point?-- I didn't have to mess with the TPS on either hexhead that I did as neither one was messed with. As long as the TPS voltage is under the idle threshold voltage & not allowing dropped throttle fuel cut-off it shouldn't effect the idle balance or stepper position as the fueling system should be idling in closed loop (fueling based on o2 sensors not BMS-K mapping)

How do you actually verify fully closed throttle plate? -- I removed them & held up to a strong light then looked through while verifying the throttle plate was closed (I mainly did this to make darn sure than the throttle plates were centered & closing evenly.

"RPM up to just above the stepper link up" By this you meant the point when the idle control is no longer in play?-- At a certain point the steppers should quit being idle steppers then link to the same counts & follow the throttle open for a ways (I t-h-i-n-k) at this point they are being used a dash pot like device to prevent a quick dropped throttle engine stall.

How can you check whether initial TB throttle cam lift starts at same time? I can recognize when they reach back to the stop screws at same time, but lift at the same time? By verifying with the TB sync tool?
--I do it 2 ways, one is to hold a hand on each TB cable cam then have someone move the twist grip. I have also watched my manometer fluid column as it is very sensitive & will show even a slight TB side lead as I slightly open the twist grip. (basically used as a verification check, if the TB cams don't start their lift at the EXACT same time then there is something drastically wrong with TB balance or engine vacuum ability)


Sorry if I bother you with so much questions, but I'm pleased to finally discuss with someone who have been working on this challenging task and have something meaningful to say--It is a very challenging task as there is no BMW defined way of re-setting those base idle screws (BMW says to replace the TB's). A flow bench would be the best way but even then we would need to know the flow rate @ what pressure drop.

Another thing to keep in mind is: There is a system voltage monitor circuit inside the fueling computer that bumps the idle RPM up (adds stepper counts) if the voltage drops to a certain point (what that point is I don't know) so make sure the battery is good & fully charged before attempting to set/balance the steppers.

Another thing that I use is large "O" ring that fits tight on the handlebar end weight, I can roll that into the gap between the end of the twist grip & the bar end weight to allow the twist grip to stay in any position that I set it (basically a poor mans throttle lock)


D.R. ___
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#999282 - 10/19/17 12:11 PM Re: Possible way to adjust messed up TB stop screws [Re: dirtrider]  
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Hello dirtrider,

Do you know what actually is the difference in idle control between hexhead and camhead? It seems to me that the same procedure can work on the camhead also.--No, I don't know ALL the differences, they are definitely close but I haven't ever compared them item for item.

You did not mention anything about the TPS in this process. Did you have to relearn it at some point?-- I didn't have to mess with the TPS on either hexhead that I did as neither one was messed with. As long as the TPS voltage is under the idle threshold voltage & not allowing dropped throttle fuel cut-off it shouldn't effect the idle balance or stepper position as the fueling system should be idling in closed loop (fueling based on o2 sensors not BMS-K mapping)
Do you know the value of this idle threshold? Is it something that can be checked with GS-911?

How do you actually verify fully closed throttle plate? -- I removed them & held up to a strong light then looked through while verifying the throttle plate was closed (I mainly did this to make darn sure than the throttle plates were centered & closing evenly.
Basics. I really hoped you have some trick to spare me the time of doing that smile

"RPM up to just above the stepper link up" By this you meant the point when the idle control is no longer in play?-- At a certain point the steppers should quit being idle steppers then link to the same counts & follow the throttle open for a ways (I t-h-i-n-k) at this point they are being used a dash pot like device to prevent a quick dropped throttle engine stall.
Spot on for the dampening functionality. I can even see that in action. Just blip the throttle to 4.000-5.000 RPM and after release it is clearly perceptible that the RPM will hold for a brief moment around 1.800 RPM

How can you check whether initial TB throttle cam lift starts at same time? I can recognize when they reach back to the stop screws at same time, but lift at the same time? By verifying with the TB sync tool?
--I do it 2 ways, one is to hold a hand on each TB cable cam then have someone move the twist grip. I have also watched my manometer fluid column as it is very sensitive & will show even a slight TB side lead as I slightly open the twist grip. (basically used as a verification check, if the TB cams don't start their lift at the EXACT same time then there is something drastically wrong with TB balance or engine vacuum ability)


Sorry if I bother you with so much questions, but I'm pleased to finally discuss with someone who have been working on this challenging task and have something meaningful to say--It is a very challenging task as there is no BMW defined way of re-setting those base idle screws (BMW says to replace the TB's). A flow bench would be the best way but even then we would need to know the flow rate @ what pressure drop.

Another thing to keep in mind is: There is a system voltage monitor circuit inside the fueling computer that bumps the idle RPM up (adds stepper counts) if the voltage drops to a certain point (what that point is I don't know) so make sure the battery is good & fully charged before attempting to set/balance the steppers.

Another thing that I use is large "O" ring that fits tight on the handlebar end weight, I can roll that into the gap between the end of the twist grip & the bar end weight to allow the twist grip to stay in any position that I set it (basically a poor mans throttle lock)


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