BMW K bikes (Bricks)

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club_c

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Well my K is running a bit better now, I want to set up/tune the throttle bodies. I have a TwinMax TB Balancer, with 2 inlets, and I have a couple of vac gauges. How would one confirm max vac being pulled, and TB's being balanced. My manual said not to mess with the adjustments on the linkage, or the linkage would have to be replaced. Too late, read that after trying to tune up. Getting an occasional exhaust pop at idle.



Last edited by club_c on Mon Sep 20, 2010 7:44 pm; edited 1 time in total

    

robmack

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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.



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1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
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badgerdid

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All i did was to turn the first screw (nearest to the front, cylinder 1 ) all the way in
Turned it back 1-1/2 turns out
Then balanced the other three to this one
Set the idle speed screw so it was idleing just about 1000 revs
Set the TPS so it clicks at throttle rest.

I now get 47-52 per gallon so i did something right.

But i dont know what your going to do now you have messed with the linkages and other screws, i should just try it and see what happens.

    

Ajays

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Setting of the TPS It has been discussed by Ned and if you set it lower to not get the first click you will find it is a lot smoother especially when cornering. There is no harsh hold back. If tuned right there is no backfire in the silencer. Try it yourself by unpluging the TPS and go for a spin. If you prefer it then set the TPS lower.
Carbtune is what I used. see attached vid.
Ajays

    

Crazy Frog

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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)


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beachcomber

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Now I admit to being a technophobe - but........................

One of the guests at my recent "Beachcomber's Pig-Roast" in Saxony was one of the Flying Brick techie guys, who just happens to be an IT whizz. All the other Brick riders there fully endorsed the product.

He's designed an electronic gizzmo that sets each individual pulse - electronically. That's the limit of my info. - it wasn't that I was'nt iterested in what he was telling me, more the fact that it was the second day of partying !

I know he made a small run of the units and is now on the Mk2 or 3 version - which is "Bluetooth" enabled, WETF that is.

If there is any interest, I'll ask him to let me have a brief description of what it is and what it does.

    

Ajays

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Sounds Great Beachy,
I am sure there would be a lot of interest. Give it a go in laymans language please. Where to get one and cost...!
Ajays
PS. Not a lot of money about. K's are going for half price here at the moment.


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ReneZ

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Bert, your procedure is not as per BMW's. It seems to start with adjusting the factory sealed throttle body link screws and then to adjust the idle with the bypass screws. The first is a no-no by BMW terms and the second is the adjustment for the 1100's that don't have the central adjustment screw. Maybe I'm misunderstanding yours above.

Kindly find below copies of the BMW manual:

Part 1

Part 2

Hope that helps.


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Greetings from Florida! Having a 'new' K  :cyclops:    Surprised-o: 

Rene


BMW K100 - 1985 (0030029)
BMW K1200GT - 2003 (ZK01223)
    

Oldgoat

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This is just great stuff guys. Thanks, as this is on the list too!

    

club_c

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Now I'm unhappy that I've changed the lockscrews on the linkages....

    

Crazy Frog

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@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. If somebody had modified the setup of the linkage (Club_C for not pointing the finger at anybody), one or many butterflies may not be totally closed at idle. If you start by setting the bypass screws, you may end up with what is passing an "unclosed butterfly" + the bypass.
If you read back the procedure that I described, the setup is not done when the bike is idling. A spacer is inserted to keep the rpm up and the butterflies are slightly open.

If you are certain that the 4 butterflies are closed, only the bypass would have to be adjusted to balance the idle but if your are not sure, the first thing would do is to sync the 4 butterflies. When you are happy with this setup, you can then balance the idle.
Here is another idea: In order to do the best job, the bypass should be totally closed when balancing the butterflies and then re-adjusted after.
What do you think? Does it makes sense?
I would like to hear about your opinion.
Cheers and thank you for expressing your opinion. It's always valuable and this is the only way that we can progress and increase our expertise.

Bert




Last edited by Crazy Frog on Sat Sep 18, 2010 11:23 pm; edited 1 time in total


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Oldgoat

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Hey Beach,
Does this guy have a website or is he strictly doing this for fellow brickheads. I would be interested in finding out more info. I'm going to be in the market for a sync tool soon.

    

phil_mars


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To throw in my two cents worth and without referring to any existing procedures the logical thing would be to make sure all butterflies open and close at exactly the same time first so adjusting the stop screws would be the obvious place to start just as it was on the older R series with separate carburettors.

To compound this issue I have seen it recommended that valve clearances be checked and adjusted if necessary before adjusting any mixture screws.

Any major discrepancies would also suggest checking for any vacuum leaks before mixture adjustment.


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Phil
    

ReneZ

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Bert, fully appreciate yours above and particularly the last bit. Indeed, some of these throttle bodies have been tinkered around with Smile

The difficulty might be to keep the bike running with the bypass screws completely closed to get a 'starting point'. I have checked a few by indeed using the idle screw arrangement to keep the valves slightly open and then use feelers to check if the clearances were the same. Others have used a drill bit (4mm or so), adjusting the idle screw that No 3 basically touches the bit and then to check/adjust the others to do the same. Its all a bit rough. I thought about creating a 'manifold' that I can connect to the bodies and the other end to the shop-vac; that would allow to use 'air flow' for a proper, constant, measurement. As with lots of things - haven't come round to it yet.
But indeed - where you don't know the history you need to go back to basics and exclude all assumptions where possible.

Hmmm, its raining again - where is that old vacuum cleaner hose I asked my wife to hold back........... Laughing


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Greetings from Florida! Having a 'new' K  :cyclops:    Surprised-o: 

Rene


BMW K100 - 1985 (0030029)
BMW K1200GT - 2003 (ZK01223)
    

beachcomber

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Oldgoat and other interested parties.

No this guy is the Chief of Police IT dept. somewhere in West Germany for his day job.

He developed and used one for his own use about 5 years or so ago from what I can make out. As usual, others wanted the device and he made a small run [ expensive]. The second run was larger to bring the costs down and incorporated several useful mods.
He is now finalising the Mk3 - which is "Bluetooth Enabled" ......................

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

All the German Brickers rave about it.

As before, I have sent a mail to his private address with the queries and just await a response before posting here.

Being Polizei, I'm not certain if he works weekends or not - but I'm certain he will respond asap.

Watch this space.

    

robmack

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@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.
Is this the unit?

Koecher Elektronik U-DIAG-II



Last edited by robmack on Sun Sep 19, 2010 9:15 pm; edited 1 time in total


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http://k75retro.blogspot.ca/
    

Ned

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@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. ...
Yep, I agree. After 26 years who knows what was done by various people including mechanics. But, having said that my understanding is that BMW uses a flow bench rig to set all butterflies the same. No magic here, you need a constant air flow and some way of measuring the restriction/flow. I have seen people use a wire gauge to do the same adjustment but there is no way of checking the flow after you do so.

I see the by-pass valve as a fine adjustment.

What are the problems with messing about with both throttle body adjustments? Well ... unless you are sure that all the cylinders are running at equal efficiency, don't touch the butterfly adjustments. Instead fix the problem first. By tuning out the problem you can really mess up the intake system.

I would not adjust butterflies until I am sure that the compression is absolutely the same. If it doesn't and you are sure that no one has played with the butterflies, you have a problem elsewhere. If you are sure that all is ok and the thing idles badly and the by-pass does not fix it, then you may attempt to check on the butterflies.




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Ned

05/1986 (K55) K100RS Motorsport (Europe), Production Code: 0503, 110k km, VIN:0140519 (SOLD)
1976 Honda Goldwing GL1000 (naked)
1997 BMW K1200RS red, VIN: WB10544A1VZA22667
    

beachcomber

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Hi Rob,

yes the very one. I got a message back waiting for me this morning from my pal.

I will put a link in as soon as I find a 5 year old to do it for me !

The situation at present is that the Mk2 version has sold out - the last of the run before the Bluetooth version comes on the market.

We are pressently discussing if RAM should handle non German sales [ English speaking ] as there is already a growing network of distributors and potential distributors for the other RAM products.

I'll get the link - or at least the site up before COP today.

TJ

    

ReneZ

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All valid comments. The difficulty is indeed that after so many years of most bikes being in different hands with different maintenance regimes by more or less knowledgeable people makes each start point an uncertainty.
There are still possibilities to get your throttle bodies adjusted as original. I am aware of a company in Germany, but the cost will be prohibitive for most if not all.
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?
Meantime I'll look for a proper cleaning way for the bodies, preferably ultrasonic. Due to size I expect that'll be expensive......Any alternatives?


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Greetings from Florida! Having a 'new' K  :cyclops:    Surprised-o: 

Rene


BMW K100 - 1985 (0030029)
BMW K1200GT - 2003 (ZK01223)
    

ReneZ

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@ BC and others - I understand there are two pieces of kit developed. Something to do with both individuals from Flyingbrick.de starting together and then falling out over further development or such. Anyway, the Germans are very happy/enthusiastic about the kit, which gives a lot more information than our mercury sticks or substitutes thereof.


__________________________________________________
Greetings from Florida! Having a 'new' K  :cyclops:    Surprised-o: 

Rene


BMW K100 - 1985 (0030029)
BMW K1200GT - 2003 (ZK01223)
    

beachcomber

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Sorry,

don't know any of the historical background re: the test kit.

I do know that the guys developing the Bluetooth version are related, and no fall outs there as both were at my Pig Roast less than 2 months ago!

As to cost - I have been told that the Bluetooth version will be considerably cheaper, due to improved manufacturing techniques and larger volume.

Also, I believe it has functions other than throttle body sync facility - but rather than vaguely guess, I'll post the info. or at least a link as and when.

    

Ned

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@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?...
Funny you should say that. My very thoughts Smile However, one has to remove the throttle bodies out to do this and that could be the most difficult bit of all.
My thoughts:
    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.



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Ned

05/1986 (K55) K100RS Motorsport (Europe), Production Code: 0503, 110k km, VIN:0140519 (SOLD)
1976 Honda Goldwing GL1000 (naked)
1997 BMW K1200RS red, VIN: WB10544A1VZA22667
    

club_c

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UPDATE: The bike ran poorly this afternoon when I started it up, missing, lumping, ugly. I pulled the plugs and found they were fouled with all the crap that got burned off the cylinders after I took it apart and cleaned it. Once the plugs were cleaned again, it ran much better.

As for balancing the throttle bodies, I took Bert's advice and closed the bypass screws completely, and then rebalanced the linkage adjustments. Then I opened the #1 bypass screw a 1/2 turn, and balanced each TB to the#1 TB in turn with the corresponding bypass screw. I did this with my Twinmax TB balancer. Now the engine is so smooth. Since I've applied for 'collector plates' I have to wait until they arrive, so the bike is not licenced/insured to ride on the road yet. The best I've been able to do is up and down my private street, barely making 2nd gear.

    

Crazy Frog

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Thank you for trusting my theory.

As always, stop, think, analyze the problem and understand the functionality of the part. Then decide of a plan of action.
This is the only way to troubleshoot and fix a problem. You don't have the sophisticated equipment owned by the manufacturer or a dealer.

I am happy that you were able to solve the balancing, but I have to point to you that the bypass screw has to be initially open by one full turn. You are then allowed to turn it CW or CCW by a maximum of 1/2 turn.
As you are now an experienced man in balancing the throttle body, you may want to review the setup of the bypass screw. It should be easy as you don't have to touch the linkage.
The bike may even run smother after this adjustment and if in the process you don't have to modify the setup of the bypass by more than 1/2 turn either way, this will prove that you did an excellent job on setting up the linkage.

Great job.

Bert


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phil_mars


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Excellent work and it really is nice when a plan comes together with the added bonus of not seeing a post specifically on this before that has been successfully resolved.


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Phil
    

26Back to top Go down    Throttle Bodies - I love this forum. on Thu Sep 26, 2013 2:08 am

OZhoppo

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The K100RS was not running as smoothly as I remembered so I thought I would have a look around the forum and came across this thread.
I went out to the bike and had a long look at the throttle body and linkage setup.   The first thing I noticed was the idle screw was not in contact with it's stop.  Looking at the butterfly screws I could see the rear-most screw was wound all the way down.  A check of the bypass screws showed 1.75, 2.75, 0 and 1 (turns out - from front to rear). 
On with the vacuum gauges and that confirmed that someone had tried to 'tune' the throttle bodies.  Making a long story short, I tested for leaks using a spray can of engine starter (all good), seated the bypass screws and then followed Bert's instruction (off idle and balance the bodies using the stop screws and then back to idle an re-balance using the bypass screws). The bypass screws are all within .25 of a turn with none more than 1.25 out
I know I should have checked compression and the valves before playing with the throttle bodies but they were so far out it just had to be done. 
It starts, idles and runs a WHOLE lot better than before

Once again, thank you Bert and the other forum members.

P.S. the valve tool is winging it's way to OZ from Motobins as I type.

    

charlie99

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good work oz .....!

how does she travel up high in the revs ....?

just wondering if it has affected the vibes at that magic 3700  and 4200 revs

cheers mate


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RT

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I'd like to ask a question here and re open this a bit. I have just put the mercury man o manometer onto my new old 90 LT to try and  get it running smoothly. After having just done my 85 RT with reasonable success,
I was surprised to see hardly any movement at all on the tubes. 1,2 and 4 were flatlined doing nothing, no matter how much I screwed in or out and 3 was reading about 10 but wouldn't move from there.

My question, is this an indication of extreme air leak?, the engine runs but lumpy and if I try and ride it it over revs with out any movement on the throttle linkages. (bearing in mind that I was the one to put the air chamber at Rubbers back on the bodies!!!!).

Thanks, RT


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RicK G

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I reckon you would be fairly right there RT. The one that doesn't move is probably blocked.


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Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

duck

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Yes, a TB that can't be sync'd is usually a sign that the rubber boot between the TB and cylinder head is leaking,  Not at all uncommon given how old these bikes are getting.


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86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
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94 K1100RS
93 K1100LT (x2)
91 K1
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RT

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Hmm, I failed to mention that when I got the bike the plenum was off and it was me who struggled to fit the tubes back on. Think I may have failed that test. Oh well, kinda getting used to that feeling, but knowing that help is just a click away is re assuring .
Thanks.


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Symbolizm

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I would just like to say a thank you to Crazy Frog, I used your well explained method today and I have to say it worked out brilliantly.  My throttle linkage did need a small amount of adjustment (cylinder 3 was out) and then I balanced the carbs and wow what a difference, the bike seems so much smoother.  So I have to say do not fear adjusting the linkage it's no big deal!  I also found that it's best not to be too anal about setting the carbs and throttle linkages up, it's always going to be a bit of a compromise and trying to get each calibration meter to read exactly the same is not always going to happen, I just aimed to get the readings as close as I could and judging by the results that was good enough.  I would just like to add that setting the TPS is quite critical, as if set incorrectly even by a small amount the engine will not sit happily at 950rpm.  I found that listening to the click method is a bit hit and miss and that if you adjust the TPS while the engine is running you can hear and watch the tacho for the correct setting.

Thanks again guys for this excellent thread.

    

33Back to top Go down    Some Questions about TB Balancing on Sat Mar 26, 2016 5:40 am

Kafflut

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@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.


Before I start I have some questions and would appreciate if someone can answer these.

1. I understand the bit about valve adjustment: "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"

Q1: I've done the valve clearance adjustment. Now I'm wondering, should I not do a compression test before I do anything else? What if I have some valve(s) in not so good condition?

2. I replaced the little rubber caps on the vacuum take-off points. I checked for leaks with carb cleaner and fixed. I also replaced the breather connecting rubber between crank case & plenum chamber. Now, "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..."

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 in the air flow meter by hand. ) I could feel the suction, but the engine still did not stall.

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?

http://bmwk100k75.weebly.com/
    

K75cster

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Yes doing a valve check is a smart idea, you can balance the T/B's without doing it but 10,000K later you will do the valves anyway and then have to rebalance so may as well set it up first.
A compression test will tell a story, if you want to listen to that story, "most of us do" Then surely do it.
By all rights and measures the T/B's will be kept open just a tad by the throttle stop screw so it may not stop, it may struggle on with that miniscule amount of air to run with. So far so good.


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35Back to top Go down    TB Balancing - Is this a good plan? on Sun Mar 27, 2016 1:27 am

Kafflut

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Thank you. I'm going to start with a compression test then.

1. Compression test. I hope I don't have to do a valve job or rings.
2. "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....."

I want to make sure the throttle plates are reasonably well synchronized. I don't know the bike's history. It was awful when I got it - those little adjusters were probably fiddled with and if not, what about wear?

3. Cobble together some vacuum measuring stuff and do TB balancing.

Thank you again. Thanks too to all who have written about TB balancing - the text I quoted in my previous post will be printed and pasted in the back of my Clymer maual.

http://bmwk100k75.weebly.com/
    

charlie99

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@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?


from the plenum to crankcase tube to start with ...eventually the crankcase will turn to vacuume and will cease flow ...given all the seals are sound and you have the oil filler cap tight ,
good luck


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