95 R1100RS TB sync dilemma

[Christo]

Greetings!

 

I have a question about the TB sync procedure: With respect to the more thorough 'zero=zero' or the newer 'zero=250mv' procedures for TB syncing and idle setting, I chose instead to do a simple idle adjust and TB sync per the BMW service manual as I've done many times.

 

The problem is this: Using a homemade manometer (air tubing on stand with 2 stroke oil connected to left/right vacuum ports) I can achieve perfect TB sync at 2500 RPM by adjusting the crossover cable, but then when the TBs are at rest, the right side TB is very close to, but not touching the stop. In the manual, I'm admonished NOT TO TOUCH THE TB STOPS, and at the same time MAKE SURE THE TBs TOUCH THE STOPS AT REST. But, also to adjust the crossover cable to have equal vacuum.  Well, I don't see how all three can be enforced at the same time, unless I touch the untouchable throttle stops.

 

Is it ok my crossover cable has slight tension when at rest, if it means good TB sync at 2500 RPM?

 

(PS: I did the full BMW recommended procedure including starting with adding ~.5mm play in the fast idle and throttle cables first)

[dirtrider]

22 hours ago, Christo said:

Greetings!

 

I have a question about the TB sync procedure: With respect to the more thorough 'zero=zero' or the newer 'zero=250mv' procedures for TB syncing and idle setting, I chose instead to do a simple idle adjust and TB sync per the BMW service manual as I've done many times.

 

The problem is this: Using a homemade manometer (air tubing on stand with 2 stroke oil connected to left/right vacuum ports) I can achieve perfect TB sync at 2500 RPM by adjusting the crossover cable, but then when the TBs are at rest, the right side TB is very close to, but not touching the stop. In the manual, I'm admonished NOT TO TOUCH THE TB STOPS, and at the same time MAKE SURE THE TBs TOUCH THE STOPS AT REST. But, also to adjust the crossover cable to have equal vacuum.  Well, I don't see how all three can be enforced at the same time, unless I touch the untouchable throttle stops.

 

Is it ok my crossover cable has slight tension when at rest, if it means good TB sync at 2500 RPM?

 

(PS: I did the full BMW recommended procedure including starting with adding ~.5mm play in the fast idle and throttle cables first)

Afternoon  Christo

 

You have just run into the early 1100 single-throttle-cable/crossover-cable rabbit hole.  

 

With that single cable system you have some choices, none of them are perfect!

 

You can leave it as it is then just lightly snug the R/H side idle screw up to the lever leaving no  gap (just lightly take the load off of the cable), this is what I typically do.

 

Or try to split the difference by having the R/H side on the idle screw but then the above-idle slightly off-balance (using a liquid manometer it probably isn't as far off as it looks as the fluid U tube manometers are still close enough even at 2" of liquid height variation. 2" of H2o is only (.141" Hg vacuum). 

 

BUT, what YOU REALLY NEED TO DO FIRST__   is: never start the engine with the choke on before a TB balance on the early single cable systems. 

 

After warming it up, shut it off, then WITH CHOKE completely OFF, fully open & close the twist grip about 3 times.

 

On the single cable systems using the choke before a TB balance works the crossover cable the wrong way on the L/H side TB cam as it pulls on the cam using a different cable. Using the twist grip with the choke OFF allows the main cable to work it's way back to the correct wrap on the L/H TB cam. (on some older 1100 single cable systems this can make a notable difference in the TB balance being correct or not ). 

 

Do not allow that R/H side to just hang on the cable at idle without at least lightly touching the idle screw. That crossover cable runs very close to the hot engine so that cable will stretch out with a very hot engine, without the idle screw to limit it the R/H side TB throttle plate can drop well below your desired stop point.  

 

 

 

 

[Christo]

Thank you DR!!

 

47 minutes ago, dirtrider said:

After warming it up, shut it off, then WITH CHOKE completely OFF, fully open & close the twist grip about 3 times.

I used this method last week when resetting the idle after replacing the fuel pump, filter, and all the plumbing, and my idle was very high afterwards (2.5k). And did this method a couple more times this week when having LOW idle issue, before finding and cleaning black gunk on the BBS tips.

 

But, I don't think I did it right before doing the TB sync. Also, I used the choke lever to maintain the 2500 RPM while doing the sync. From your excellent writeup, that may not be the way to do it?

 

I'll try again with the throttle twists first, and the choke completely off the entire time, and report back. 

 

[JamesW]

I gave up on the choke completely on my '93 RSL and physically removed the choke cable.  The so called choke is really just a throttle positioner nothing more and doesn't richen the idle mixture as would an actual choke like what we think of when we use the term choke.  When I start the bike cold I just give it a tiny bit of throttle and hit the start button.  She fires right up and I allow it to fast idle maybe 30 seconds at about 1500 rpm using the throttle and away I go.  That so called choke always causes the TBs to go out of sink and you can feel it.  Only way to cancel this effect is to shut it down and roll the throttle full on and off then restart.  

[Christo]

 

To update, I followed DR's advice by resetting the throttle before any syncing, NO CHOKE, and making sure I have no gap in the right TB after syncing. I did this by dropping the right TB a little instead of raising the TB stop, observing how this affected the oil in the manometer, and the effect was minimal. I do have a tiny bit of surging at low speeds, but per your advice, this it preferable to a taut crossover cable. I may someday be brave enough to adjust the stops, knowing I may need to ship the bike to Munich to have it corrected. :o)

 

 

On 11/16/2023 at 5:36 PM, JamesW said:

I gave up on the choke completely on my '93 RSL and physically removed the choke cable.  The so called choke is really just a throttle positioner nothing more and doesn't richen the idle mixture as would an actual choke like what we think of when we use the term choke.  When I start the bike cold I just give it a tiny bit of throttle and hit the start button.  She fires right up and I allow it to fast idle maybe 30 seconds at about 1500 rpm using the throttle and away I go.  That so called choke always causes the TBs to go out of sink and you can feel it.  Only way to cancel this effect is to shut it down and roll the throttle full on and off then restart.  

Interesting! Something to think about. Maybe that's why I always end up with a little surging. You and DR are giving me some very helpful info about the pitfalls of the choke cable. 

 

About the right TB stop: After a perfect TB sync, the right TB can be made to seat against the stop by snapping loose the throttle, making a 'clunk', rather then letting off the throttle slowly. Also, you can grab the TB cam and seat it manually and it will stay. I thought this might be because of gunk on the TB cams or cables, so I cleaned them with brake parts cleaner, then a light spritz of WD-40, but same behavior.

 

 

[dirtrider]

7 hours ago, Christo said:

 

To update, I followed DR's advice by resetting the throttle before any syncing, NO CHOKE, and making sure I have no gap in the right TB after syncing. I did this by dropping the right TB a little instead of raising the TB stop, observing how this affected the oil in the manometer, and the effect was minimal. I do have a tiny bit of surging at low speeds, but per your advice, this it preferable to a taut crossover cable. I may someday be brave enough to adjust the stops, knowing I may need to ship the bike to Munich to have it corrected. :o)

 

 

Interesting! Something to think about. Maybe that's why I always end up with a little surging. You and DR are giving me some very helpful info about the pitfalls of the choke cable. 

 

About the right TB stop: After a perfect TB sync, the right TB can be made to seat against the stop by snapping loose the throttle, making a 'clunk', rather then letting off the throttle slowly. Also, you can grab the TB cam and seat it manually and it will stay. I thought this might be because of gunk on the TB cams or cables, so I cleaned them with brake parts cleaner, then a light spritz of WD-40, but same behavior.

 

 

Morning  Christo

 

That isn't your surging issue. No amount of TB sync will stop the light throttle surging on the 1100. 

 

Even using the choke to start it isn't causing the light throttle surging as the migrating cable wrap when using the choke to start it quickly goes away after using the twist grip during normal riding as that works the cable to TB pulley wrap back in the proper direction. The secret here is to just not do the TB sync after starting it using the choke.

 

The light throttle surging on the 1100 is a compound issue, typically caused by emission era mandated lean fueling with single spark plug cylinder heads. 

 

Removing the CCP (if your 1995 RS has one), or cutting the CCP selection wire (on non-CCP equipped early 1100RS bikes) usually makes the light throttle surging go away. Or on some extreme surgers, almost go away.

 

You can try adding an aftermarket fuel controller (like an af-xied)  but on the very early 1100 motorcycles (like the 1100RS)  it usually needs to be set so rich to stop the surging that it brings on other over-richness problems. 

 

On your R/H side not always hitting the throttle stop screw?-- As the engine gets hot & the crossover cable stretches out that usually allows the R/H side to lightly contact the throttle stop screw. 

 

A number of riders (& some dealers)  converted the early 1100 motorcycles with crossover cable system to the later Boden box with independent cables for each side. (made keeping/maintaining the cable adjustment much easier & a lot longer lasting).     

[JamesW]

I can tell you that cutting the code plug jumper on my '93 completely cursed the surging and interestingly the computer no longer recognizes the O2 sensor at all.  Fuel economy dropped maybe 2 mpg if that.  There was no need to use a fuel enhancer at all.

 

I have wondered if all R1100 bikes that use the 2.2 Moronic ECU would respond the same way by either cutting the jumper or if so equipped removing the cat code plug.  I read that the 2.2 Moronic has been revised many times.  I know that on the R1150 machines with the 2.4 Moronic removing the CCP does not result in improved running.  Just the opposite.

[dirtrider]

32 minutes ago, JamesW said:

I can tell you that cutting the code plug jumper on my '93 completely cursed the surging and interestingly the computer no longer recognizes the O2 sensor at all.  Fuel economy dropped maybe 2 mpg if that.  There was no need to use a fuel enhancer at all.

 

I have wondered if all R1100 bikes that use the 2.2 Moronic ECU would respond the same way by either cutting the jumper or if so equipped removing the cat code plug.  I read that the 2.2 Moronic has been revised many times.  I know that on the R1150 machines with the 2.4 Moronic removing the CCP does not result in improved running.  Just the opposite.

Evening James

 

Your early Motronic 2.2 only has a couple of maps so you only have the choice of closed loop or open loop (no o2 sensor feedback control).

 

The later CCP equipped Motronic computers have a number of internal maps.

 

Removing the CCP and forcing open loop operation on the later (CCP equipped) Motronic 2.2 bike does help a lot for removing light throttle surging. Personally, I don't think it is quite a dramatic as on the early 2 map Motronic's but still makes a big difference.

 

A good sign that removing the CCP (or cutting the CCP wire) is going to help remove surging is IF removing the CCP or cutting the wire jumps the idle RPM up a noticeable amount. That idle speed gain is caused by more fuel being added at idle & that richer idle fueling carries up into the above-idle fueling range far enough to help remove the factory lean-induced surging.  

 

 

[Christo]

On 11/19/2023 at 6:41 AM, dirtrider said:

That isn't your surging issue. No amount of TB sync will stop the light throttle surging on the 1100. 

That sounds right. I recall trying to eliminate all surging years back and was never able to completely. 

 

On 11/19/2023 at 6:41 AM, dirtrider said:

You can try adding an aftermarket fuel controller (like an af-xied) 

I forgot to mention I do have a Booster Plug installed. Year back I tried it off and on, and it offered a little help. I even corresponded with the manufacturer. But alas, I'm ok with the tiny amt of surging and am used to it. It accelerates great. 

 

And thanks DR for the advice on the cable. I won't worry if it's very close. DR, I recall your past advice on converting to the Boden box, and was thinking about doing that at some point, say when my cables get too stretched or one breaks.  

 

Thanks JamesW and DR for the advice on cutting the wires. In the past I read a bunch on the closed/open loop variations and CCP delete and have to date just been running stock. I get about 38-40mpg highway. With ethanol free gas, 42-44mpg highway. It does smell rich when starting/idling in the garage, but not sure what normal is, or if I should be getting much higher mpg.

 

My current issue is low and rough idle. I mentioned in another thread I installed an aftermarket fuel pump, and it subsequently started making intermittent buzzing sounds, but runs great on the road. But low idle. I'm still debugging that, and will return to that thread, or start a new one if I don't get it solved with throttle reset or BBS adjustments.   

[dirtrider]

3 minutes ago, Christo said:

That sounds right. I recall trying to eliminate all surging years back and was never able to completely. 

 

I forgot to mention I do have a Booster Plug installed. Year back I tried it off and on, and it offered a little help. I even corresponded with the manufacturer. But alas, I'm ok with the tiny amt of surging and am used to it. It accelerates great. 

 

And thanks DR for the advice on the cable. I won't worry if it's very close. 

 

Thanks JamesW and DR for the advice on cutting the wires. In the past I read a bunch on the closed/open loop variations and CCP delete and have to date just been running stock. I get about 38-40mpg highway. With ethanol free gas, 42-44mpg highway. It does smell rich when starting/idling in the garage, but not sure what normal is, or if I should be getting much higher mpg.

 

My current issue is low and rough idle. I mentioned in another thread I installed an aftermarket fuel pump, and it subsequently started making intermittent buzzing sounds, but runs great on the road. But low idle. I'm still debugging that, and will return to that thread, or start a new one if I don't get it solved with throttle reset or BBS adjustments.   

Afternoon  Christo

 

The Booster plug won't do a darn thing when in closed loop operation & if you are running in stock configuration then your surging is happening when in closed loop operation.  

[JamesW]

Thanks D.R. for your explanation regarding early 2.2 R1100 bikes.  Kind of what I thought  but wasn't sure.  I made contact with Bosch and asked if their repair services would address any issues I might have going forward with my 31 year old Moronic and they told me that they had no record my early 2.2 even existed.  Ahhhh..nothing like superb German engineering I always say or maybe their superb system of record keeping.

[dirtrider]

14 minutes ago, JamesW said:

Thanks D.R. for your explanation regarding early 2.2 R1100 bikes.  Kind of what I thought  but wasn't sure.  I made contact with Bosch and asked if their repair services would address any issues I might have going forward with my 31 year old Moronic and they told me that they had no record my early 2.2 even existed.  Ahhhh..nothing like superb German engineering I always say or maybe their superb system of record keeping.

Afternoon James

 

As long as your going to use it open loop then about any  1100 Ma 2.2 Motronic should work. Especially if you swap your existing cal chip into it.