R1200 series Throttle Body Sync Pictorial

Mark, I read somewhere (I'll have to search a bit to see if I can find the reference) that it is possible to adjust the stepper such that it binds up and cannot be fixed. I thought that the source of info was reputable at the time. The story was that they had to buy a new TB to solve the issue.

Some comments about idle sync from an amateur....

The RepROM states that an idle imbalance of up to 25 mbar is allowed. I assume that is with the steppers parked. Until the GS-911 adds that function I'll just have to trust that things are close enough without parking the steppers. Anyway, the manual states that if the imbalance exceeds 25 mbar at idle you should

1) check for air leaks
2) check the valves

This makes lots of sense to me. I'd be very wary of playing with the stop screws when making sure that the valves match side-to-side might be all that is needed. I've watched folks do valve adjustments and while all are very careful to make sure that the valves on each side match, some are not so careful about matching side-to-side. That is, one side may be slightly tighter than perfect while the other side is slightly looser than perfect.

If my idle goes to hell I'm going to take extra care on the valve settings.

I can give you some information on the stepper motor from the automotive application, how much it translates to BMW MC's, I don't know.

The stepper motor controls idle by bleeding air past the throttle plate, it is also responsible for the air bleed (idle increase) during cold start.

When we would set the base idle, it was done using a scanner and monitoring the stepper motor reading. Engine at normal operating temp. The base idle was adjusted until a specific stepper reading was reached.
(base idle was set by changing throttle plate position using a stop screw or an additional air bleed screw)
I needed the scanner because as the throttle plate was opened the stepper would close and vise versa, rpm's would stay the same. not reading the stepper motor position could cause it's operating limit to be exceeded.

The stepper motor had a given operating range, if it was exceeded it would damage the motor in short order.

I would think BMW could recalibrate the throttle bodies without replacing, they have to do it anyway. Turn around time might be another issue. I would guess that a good service tech can also come close by reading the stepper motor on your bike but the key word is guess.

I for one would not touch these screws unless I could read the stepper position and return it to that setting. Even then it's the idle and I'm not usually at that position too long.

Hope this helps.

To add to this I'm not a fan of unplugging them to check idle balance. There are two and to unplug them and get them in sync would be a challenge. They constantly change and would cause balancing to two different stepper settings, unless you can lock them equally, I would leave them plugged in.

New2rt said:

To add to this I'm not a fan of unplugging them to check idle balance. There are two and to unplug them and get them in sync would be a challenge. They constantly change and would cause balancing to two different stepper settings, unless you can lock them equally, I would leave them plugged in.

Click to expand...

Stepper motors inherently "self-lock" when de-energized. They resist moving from the "step" they're in. And on the R12 series - the two move in sync. They don't move independently of each other.

The latest GS-911 beta software has the ability of "locking" the steppers for balance adjustments, and has had the ability for some time, of reading the stepper motor positions. That's how we found out the two move in sync.. so to me - it really doesn't matter if the TB balance is done with them connected or disconnected - since they're in sync, and only really effective at or very close to idle (which isn't where we're balancing the TBs) - they have no effect on the end result.

One thing I believe is coming on the GS-911 will be the ability to change the base settings of the steppers so as to be able to adjust the idle speed. Not that I've ever had my bike stall on me - but having the ability might be nice.

Mark, the perfectionist in me likes what you're thinking of doing.. the hesitant to touch screws that are never to be touched engineer wouldn't suggest doing it.

I'd love a perfect idle on my R12R - but since I don't ride at idle, I found I am capable of ignoring less than perfection - especially since it's a bit temperature dependent. I agree with your analysis - and the caution Marchyman makes - make sure everything else is perfect before making adjustments to the TBs.

So far on my bike - if I get the valve adjustment what I consider anally perfect - sync above idle is as perfect as I can measure on my TwinMax at maximum sensitivity. Maybe I'm lucky - but I'm guessing BMW did get it right when they initially set it up. Given that perfection where I actually ride the bike - I've decided to just ignore the slight rocking at idle - and think of it as character.

BTW - you might take a look at the DIY/Tech area - there are some great writeups there with very clear illustrations of what is being adjusted and why..

Best,

deilenberger said:

Stepper motors inherently "self-lock" when de-energized. They resist moving from the "step" they're in. And on the R12 series - the two move in sync. They don't move independently of each other.

The latest GS-911 beta software has the ability of "locking" the steppers for balance adjustments, and has had the ability for some time, of reading the stepper motor positions. That's how we found out the two move in sync.. so to me - it really doesn't matter if the TB balance is done with them connected or disconnected - since they're in sync, and only really effective at or very close to idle (which isn't where we're balancing the TBs) - they have no effect on the end result.

One thing I believe is coming on the GS-911 will be the ability to change the base settings of the steppers so as to be able to adjust the idle speed. Not that I've ever had my bike stall on me - but having the ability might be nice.

Click to expand...

I ordered the GS911 but it is currently backordered, from what I read it has the ability to zero the steppers and until I get it I'm not sure what this means (lock for throttle sync or sync to each other) I figured they moved together but did not know if they were at the exact same setting as compared to each other.
(same as a throttle sync, they move together but one will be at a different setting as compared to the other) Hope you understand what I'm trying to say cuz I sure don't

New2rt said:

I ordered the GS911 but it is currently backordered, from what I read it has the ability to zero the steppers and until I get it I'm not sure what this means (lock for throttle sync or sync to each other) I figured they moved together but did not know if they were at the exact same setting as compared to each other.
(same as a throttle sync, they move together but one will be at a different setting as compared to the other) Hope you understand what I'm trying to say cuz I sure don't

Click to expand...

The steppers show the same number of steps at all times - ie - they move in sync. No independent control apparently (which is actually understandable since we don't ride at idle..) And yes - even the current GS-911 software has the ability to zero the steppers (I've done it - idle drops, then the ECU takes over again and brings it back up if the engine is running..) but since they move in sync, I see no reason or need to use it for balancing the TBs.

Great Discussion..Another Issue..

Another issue related to balancing induction via throttle body cable adjustments with, in my case, a TwinMax...throttle body cable end or free play...specs call for .5-1mm at TBs and .5mm at grip [R12s]...how do you folks adjust this and how do you get them equal, right/left, and within specs?

Also we balance via only one TB cable, in Jim's video and in Haynes manual the right side, that seems counter intuitive to me to only increase or decrease one side to match the other...plus doesn't that then change the free play balance?

Thanks for any ideas or comments...

Wallowa said:

Another issue related to balancing induction via throttle body cable adjustments with, in my case, a TwinMax...throttle body cable end or free play...specs call for .5-1mm at TBs and .5mm at grip [R12s]...how do you folks adjust this and how do you get them equal, right/left, and within specs?

Also we balance via only one TB cable, in Jim's video and in Haynes manual the right side, that seems counter intuitive to me to only increase or decrease one side to match the other...plus doesn't that then change the free play balance?

Thanks for any ideas or comments...

Click to expand...

I've never thought of it in terms of any sort of "balance" of cable slack -- the slack specs are there to ensure that the throttle plates will definitely go to their rest positions when the throttle grip is released, no matter what effect temperature/handlebar turn angle/etc. may be having on the cables. There is no need for the slack to be "matched" -- only that there be at least a sufficient minimum slack at all the cable ends.

In fact, you can't balance vacuum if you are constrained to keep the slack exactly the same. Balancing is done because the cables are two microscopically different lengths -- balancing effectively shortens or lengthens one cable so that when the throttle grip is operated, both cables pull their throttle valves open at the time. Maintaining equal slack precludes "matching" of the cable lengths.

I tune for vacuum balance, and then double check afterwards that there is enough slack at all the cable ends. If not, I mutter under my breath and then adjust the cables generally equally on both sides to increase the slack, and re-sync the vacuum balance (and then again double check for the existence of slack).

That said, I rarely have to adjust slack -- the balancing adjustments are so small that they rarely ever eat up enough slack to require adjustment.

As to which side, it used to be that BMW called for adjustments on the right side. With the newer, different throttle cable arrangements, it doesn't matter which side you adjust, as long as sufficient slack is available -- and there should be no need to adjust both sides (again, unless there's insufficeint slack on one side), because you are only changing the relative flow between the sides (i.e., adjusting up on one side would have the same effect as adjusting down on the other).

HTH!

Thanks For Input..."Balancing" Can Be Affected By Slack

mneblett said:

I've never thought of it in terms of any sort of "balance" of cable slack -- the slack specs are there to ensure that the throttle plates will definitely go to their rest positions when the throttle grip is released, no matter what effect temperature/handlebar turn angle/etc. may be having on the cables. There is no need for the slack to be "matched" -- only that there be at least a sufficient minimum slack at all the cable ends.

In fact, you can't balance vacuum if you are constrained to keep the slack exactly the same. Balancing is done because the cables are two microscopically different lengths -- balancing effectively shortens or lengthens one cable so that when the throttle grip is operated, both cables pull their throttle valves open at the time. Maintaining equal slack precludes "matching" of the cable lengths.

I tune for vacuum balance, and then double check afterwards that there is enough slack at all the cable ends. If not, I mutter under my breath and then adjust the cables generally equally on both sides to increase the slack, and re-sync the vacuum balance (and then again double check for the existence of slack).

That said, I rarely have to adjust slack -- the balancing adjustments are so small that they rarely ever eat up enough slack to require adjustment.As to which side, it used to be that BMW called for adjustments on the right side. With the newer, different throttle cable arrangements, it doesn't matter which side you adjust, as long as sufficient slack is available -- and there should be no need to adjust both sides (again, unless there's insufficeint slack on one side), because you are only changing the relative flow between the sides (i.e., adjusting up on one side would have the same effect as adjusting down on the other).

HTH!

Click to expand...

Thanks...lots of info here...when I mentioned 'balance' in my post it referred to induction balance...AKA 'synchronisation' of right to left TBs...evidently that balancing out of TBs can be affected by the amount of free play/slack/end play...let me quote the Haynes manual:

"Note: It is essential that freeplay is the same in both cables, otherwise the operation of the throttle valves will not be synchronised"

Your description of fiddling with the slack and synch painted a good image...and one I can relate to...my original question was how do we measure that ".5-1mm" freeplay? I guess we just eyeball it. What I hear is that freeplay is not critical [if within specs?], but that it should be the same on both cables...or at least within specs...which at .5-1mm means they are damn near identical...as I understand the freeplay is between the cable housing the metal adjuster at the TB...the cable does not have freeplay...If cable housing is too loose or too tight it can affect the operation of the cable inside that housing.

OK...back to the shop and another shot at it!

Thanks again..

Wallowa said:

let me quote the Haynes manual:

"Note: It is essential that freeplay is the same in both cables, otherwise the operation of the throttle valves will not be synchronised"

Click to expand...

The number of mis-statements and errors in the Haynes and Clymer manuals would fill a book ... um, come to think of it, they do.

It is not "essential" that the freeplay be the same on both sides -- only that some freeplay exists. The 0.5-1 mm spec is really there to make sure people don't leave just an RCH of slack, and then later have a throttle butterfly hung open. At the other end of the slack spec, you actually could put as much slack in as you want (but you wouldn't, as you'd be annoyed with how far you have to crank the throttle grip before the cables start moving the butterflies).

Wallowa said:

...my original question was how do we measure that ".5-1mm" freeplay? I guess we just eyeball it.

Click to expand...

Sorry if I wan't clear. Yes -- if you can lift up on the cable ferrule and see at least a half mm of slack, it's fine.

Wallowa said:

but that it should be the same on both cables...or at least within specs...which at .5-1mm means they are damn near identical...

Click to expand...

Nope -- see above comments regarding Haynes

Wallowa said:

as I understand the freeplay is between the cable housing the metal adjuster at the TB...

the cable does not have freeplay...If cable housing is too loose or too tight it can affect the operation of the cable inside that housing.

Click to expand...

Yep!

deilenberger said:

The latest GS-911 beta software has the ability of "locking" the steppers for balance adjustments, and has had the ability for some time, of reading the stepper motor positions.

Click to expand...

Beta? Oh, I see there is a new one. Thanks for that info. The previous release would let you sync the steppers side-to-side, but not lock them. Time to do some downloading. Good timing, too... my 48K service is around the corner.

deilenberger said:

The steppers show the same number of steps at all times - ie - they move in sync. No independent control apparently (which is actually understandable since we don't ride at idle..) And yes - even the current GS-911 software has the ability to zero the steppers (I've done it - idle drops, then the ECU takes over again and brings it back up if the engine is running..) but since they move in sync, I see no reason or need to use it for balancing the TBs.

Click to expand...

Huh, I did not know that, I was thinking they can self adjust to allow an equal power pulse at idle from each cylinder. Now I see why that special screw begs to be turned. My bike is new and I'm sure breaking the seal would not be good for warranty and actually I kind of like the character idle.

Thanks for the information