• - First - do you have a manual, if so which one? If not BUY one right now. Clymer or Haynes.
  
• - The bike needs to be checked for intake leaks. At 23 years old - you more than likely have some. Move the bike outside your garage. Have a fire extinguisher handy. Start the bike, let it idle. Take some FLAMMABLE carb cleaner spray and spray very small spritz's around the injectors and the throttle bodies. ANY CHANGE in idle indicates a leak. FIX THE LEAKS before going any further. Try not to start a fire - there is hot exhaust right on the bottom of the head. If you don't know if your skill level is good enough for doing this STOP and find someone who has the necessary skill level. I don't want you burning your house down.
  
• - The bike has to have the valves precisely adjusted. You're going to be using the engine as an air-pump for a flow bench. Without the valve adjustment it just isn't going to work. They have to be adjusted right, and the closer you can get them to each other the better this is going to work.
  
• - OK - once the above is done - remove all the brass screws. Clean them and use a Q-tip in carb cleaner to clean the bores they go into. Replace the O rings on them. Screw them in until they *gently* bottom out - then open each of them exactly one turn. IF there are any steps on them from over tightening them - replace them. You can't adjust damaged ones.
  
• - Remove the throttle-position-switch from the rearmost TB. We'll get to replacing and adjusting it when we're all done here.
  
• - Connect the 4-channel vacuum gauges. Start the bike. See how it looks at idle. Since you've already misadjusted the inter-TB screws, we'll start there. Adjust these screws until all channels read the same. We're not worrying a lot about idle speed, but don't turn them all in the same direction. Balance the vacuum on them.
  
• - Open throttle to 2,000 RPM. Do all of the channels change at the same rate? If not - you're going to have to adjust the inter-TB screws at 2,000 RPM until they do. Once you get that right, we're going back to an idle balance adjustment
  
• - Once all channels look the same at 2,000 RPM, drop back to idle (~1,000 RPM). If the channels aren't balanced - use the brass screws to balance them out. You should not have any brass screw more than 1/2 turn different from the rest. If you do - then the inter-TB screws still aren't correct, and you have to repeat the steps above. (ALL brass screws should be between 1/2 turn and 1.5 turns out. None should be out more than 1.5 turns, and none in more than 1/2 turn.
  

ReneZ wrote:Bert, your procedure is not as per BMW's.

beachcomber wrote:I'm not certain if the Mk2 [ non-Bluetooth ] will still be available - I'll check.

All the German Brickers rave about it.

Crazy Frog wrote:

ReneZ wrote:Bert, your procedure is not as per BMW's.

Renez,

I don't know if I am wrong, but a forum is a place where we debate until we find the right answer and I don't have any problems with people questioning a solution and coming with a better one or different approach. We are all here to learn from each other.

Let me explain why I think this procedure is the best.
BMW assumes that the settings are still the same as the factory ones. ...

ReneZ wrote:...
I still feel that the option of using an old vacuum cleaner with a proper 'manifold' and bypass regulator should allow quite a precise adjustment/verification for the butterfly valves interlinks as well as the final setting with the bypass screws, with minimal adjustment required on the bike, if any. Any thoughts on that?...

a. one can use an old manifold rubber and bolt it to a plate to which the vacuum cleaner is connected. the throttle body (one at the time) can be connected to the manifold and by use of the vacuum port (with the by-pass closed) you can make adjustments to set all butterflies the same.
b. alternative is to use a wire gauge to make all butterfly to throttle body the same. I don't see the problem with this because the final adjustment is made using the by-pass valve when the bike is running.

robmack wrote:I don't profess to be an expert in TB syncing so I am quoting the experts:


K throttle Body Synching

By: Rob Lentini
June 1995
Here's a real simple way to ascertain whether your K'sthrottle plates are in synch--the adjustment we are admonished to never touch!
Attach a carb stix, other mercury synchronizer, or veryaccurate bourdon tube vacuum gages to each vacuum access port (covered byrubber caps and the fuel pressure regulator line). Connect the loose fuelpressure regulator vacuum line to the corresponding carb stix column (or gauge)using a "T" fitting.
Warm the engine. Screw in and lightly seat all three (orfour) idle bypass synch adjustment screws (count the turns in for each, andrecord). Doing this will slow or stall the engine, so actuate the startinglever (choke) to maintain normal idle speed**[see amended procedurebelow-wd]**.
When the screws are fully seated, any measured vacuumimbalance is then a function of variance in throttle plate opening ONL Y, andis adjustable from between the throttle bodies. If out of synch, carefullyadjust to equalize all readings. At this point, increase RPM slowly andsmoothly, checking for different readings at various engine speeds.
You should see little or no change, since adjustment atthe smallest throttle opening is most critical. Once throttle plate synch isset, reopen the idle bypass synch adjustment screws (per your notes), andfine-adjust them to re-establish correct idle speed and synchronization withthe "choke" lever off.
Following this procedure should not affect the adjustmentof the throttle switch/position transmitter. Check if in doubt. On older Ksyou're listening for an audible "click" just as the throttle returnsto the closed position. Follow this procedure and your perfect throttle bodysynchronization will eliminate much vibration.

*AMENDED PROCEDURE*
I stand corrected! A few days ago I shared with all a procedureto synch the throttle bodies of K motors. In it, I suggested using the chokelever to maintain idle speed while the bypass screws were closed and thebutterflies checked for equal vacuum (and adjusted if required).
Joe Senner and Tom Coradeschi pointed out a problem, one Ihadn't thought about. Their contention was that the choke opens the butterfliesfrom the aft end, while the throttle cable itself actuates from the center.Both guys said vacuum differences would be measured between these two methods,and opening the throttle through the twist grip was the correct way.
Anal as I am, I assured Tom I would verify his empiricaldata right away, so I jumped on the K last night to vindicate myself (everybodyhas an ego!).
Using my Carb Stix, I measured a 2-3 cm delta in themercury column between injector body number 3 (the aft one) and the other twowhen switching from throttle to choke actuation. Whether this is enough tocause vibration or rough running is debatable. Yet, the whole point of doing thesynch procedure is to "knats ass" the adjustment.


And the following comes from Don Eilenberger from another forum.  Also good advice for an owner who had fiddled with the linkage screws:

Well - let’s try getting it back to some semblance ofrunning correctly.

• - First     - do you have a manual, if so which one? If not BUY one right now. Clymer     or Haynes.
  
• - The     bike needs to be checked for intake leaks. At 23 years old - you more than     likely have some. Move the bike outside your garage. Have a fire     extinguisher handy. Start the bike, let it idle. Take some FLAMMABLE carb     cleaner spray and spray very small spritz's around the injectors and the     throttle bodies. ANY CHANGE in idle indicates a leak. FIX THE LEAKS before     going any further. Try not to start a fire - there is hot exhaust right on     the bottom of the head. If you don't know if your skill level is good     enough for doing this STOP and find someone who has the necessary skill     level. I don't want you burning your house down.
  
• - The     bike has to have the valves precisely adjusted. You're going to be using     the engine as an air-pump for a flow bench. Without the valve adjustment     it just isn't going to work. They have to be adjusted right, and the     closer you can get them to each other the better this is going to work.
  
• - OK -     once the above is done - remove all the brass screws. Clean them and use a     Q-tip in carb cleaner to clean the bores they go into. Replace the O rings     on them. Screw them in until they *gently* bottom out - then open each of     them exactly one turn. IF there are any steps on them from over tightening     them - replace them. You can't adjust damaged ones.
  
• - Remove     the throttle-position-switch from the rearmost TB. We'll get to replacing     and adjusting it when we're all done here.
  
• -     Connect the 4-channel vacuum gauges. Start the bike. See how it looks at     idle. Since you've already misadjusted the inter-TB screws, we'll start     there. Adjust these screws until all channels read the same. We're not     worrying a lot about idle speed, but don't turn them all in the same     direction. Balance the vacuum on them.
  
• - Open     throttle to 2,000 RPM. Do all of the channels change at the same rate? If     not - you're going to have to adjust the inter-TB screws at 2,000 RPM     until they do. Once you get that right, we're going back to an idle     balance adjustment
  
• - Once     all channels look the same at 2,000 RPM, drop back to idle (~1,000 RPM).     If the channels aren't balanced - use the brass screws to balance them     out. You should not have any brass screw more than 1/2 turn different from     the rest. If you do - then the inter-TB screws still aren't correct, and     you have to repeat the steps above. (ALL brass screws should be between     1/2 turn and 1.5 turns out. None should be out more than 1.5 turns, and     none in more than 1/2 turn.
  

Once all this is done - the vacuum gauges should move in sync with each otherfrom 1,000 RPM - to about 5,000 RPM. If they don't - repeat the steps above.

Doing this without eliminating any leaks and adjusting the valves is futile,and I'd suggest taking the bike to a dealer if you can't do these first. Youcan only do this - and even then it's going to be difficult - with thecylinders drawing the same vacuum.

Hopefully at this point - you have balanced TB's. You should use the centralidle adjustment screw to set the basic speed. If you didn't unscrew all thebrass screws more than 1.5 turns out - it should fall within the range of thisscrew.

Finally - reinstall the TPS that we removed above. Turn it counter clockwiseuntil you JUST hear it click with the throttles closed. Turn the grip to fullyopen the throttle-bodies and you should hear it click again. What you don'twant to happen is have the throttle-bodies held open by this switch.

Kafflut wrote:


Q2: I did experience the "slowing down" but not "stalling" This made me wonder, why does it not stall? I took off the air filter box, the air flow meter and the connecting hose to the plenum chamber and put my hand over the opening in the plenum. (By the way, I also slightly opened the little flap

Why not? Where is it getting air from? Is there a leak I did not detect with the carb cleaner? Surely the  design spec for the plenum/TBs etc would be air-tight, not almost-but-not-quite-air-tight?

Crazy Frog wrote:Here is the procedure for a K75. The same applies to the K100 (1 extra cylinder).
As pointed by Don Eilenberger, the bike needs to be checked for intake leaks first.
You should also adjust the valves and clean the air filter before modifying the setup of the throttle body.

Start your engine and warm it up to its normal operating temperature.
Remove the 2 caps on vacuum ports (#4) and connect the 2 vacuum gauges (or mercury columns).
Remove the hose going from the Throttle body to the pressure regulator (#5). Install a tee and connect the 3rd vacuum gauge (or mercury columns) on the tee. (We want to keep the pressure regulator in line as we want to do a dynamic balancing in the same condition as if the bike was normally operating)
Unset or remove the Throttle Position Switch located at the end of the throttle body.
Slack off the main throttle adjusting screw (#2). Screw it back until it comes in contact again. Then screw it 1 full turn again.
Start  the engine and set it to run between 1,250 and 1,500rpm. You can slide a small spacer under screw #2 to maintain a constant rpm. (A higher rpm will decrease the depression and makes it harder to adjust).
The 3 mercury columns should be at equal level. If not, adjust screw #3 on cylinder 1 and 3 to get a good balance. Cylinder #2 is the reference.
When you are happy with the balancing, stop your engine.
Remove the spacer inserted under screw #2.
Re-install the TPS and set it up (you should hear the ‘click’ of the switch when screw #2 comes in contact).
Screw in the idle screws until they bottom up (lightly). Unscrew them a full turn.
Start your engine and balance the idle on each cylinder by turning screws #1 . You should not have to turn them more than 1/2 turn CW or CCW.
Note: if you are using a Carbtune II, it comes with piece of hose having a smaller diameter. This is a restrictor to help stabilize the reading. You should cut it in 4 equal parts and insert them at approximately 4” (or 10 cm) from the throttle body. (You have to cut the 4 long hoses)

StefanMolzen wrote:. . . at can’t find any logic in the adjustment of the TB.

Whenever I have worked on something out of my depth, Stefan, I have resorted to following instructions because I couldn't use logic. I always start with the BMW service manual then supplement it with Haynes, Clymer and/or anecdotal instructions from experienced, credible rider-wrenchers when I still need clarity. In this case, the BMW service manual made it simple for me. I use a 4-tube Carbtune for the procedure but a 2-tube tool is suitable. This method worked for me the first time and has worked all succeeding times. 

SunnyPerth wrote:As I see it,  as soon you open the throttle the switch has to click again. So with that the answer above is  (1),  move the switch until you hear it click and then tighten it.
If you would move it back to just before, it would never make contact (click) when you open throttle.

And you right, no answer to the above, and I can only imagine that if you remove the switch, you need to leave it in the throttle body closed position. Else you tune the bike when it thinks it’s getting throttle.

Just not sure (have not measured it yet) if that means the switch is open or closed. Anyways. Someone seems to have messed with the inter throttle body adjust ment screws on mine, so I’m in for a bit more fun once I find some time.