My current TB's are cosmetically poor and my options are , replace with better, pull apart and clean existing, hide them behind a cover.

Given I rebuilt (pulled apart and cleaned) my Speed triple TB's.

Ta Da!!










I want to do the same with my K100 ones but am concerned about all the dire warnings relating to the imminent end of the universe if the synch screws that alter the relative angles of the butterflies (rather than the air bypass screws) are even glanced at.

I appreciate that the TB's would have originally been set up on a flow bench but that was when they were shiny and new, 30 years must have taken its toll and can it really be any more difficult than balancing a set of carbs from an in line 4 (insert Japanese 4 cylinder model) engine??

I've read the various posts on synching K100 TB's and the theory looks to be the same as the aforementioned 4 carb method.

So has anyone pulled their TB's apart, cleaned and successfully reinstalled them???

Cheers

Fent

I did the TBs on my K1100 by pulling them apart and didnt even have to touch the adjustments and when I put them back together they were fine. I checked the opening sync with 4 dial gauges and after a lot of stuffing around I found that they were all good.
That was the spare set but the originals were all over the place and I got them very close by the method with the dial gauges and also used a small new drill bit to get the openings the same. I abandoned them because of some wear on the shafts and didnt finish the job.

There was a write up that someone did for the forum on how he did it and when I read it it was common sense stuff and methodical work and there is no reason that anybody couldn't do it.

I cleaned mine and rebalanced using a 4 port carbtune. It ran like a top after that.

I did exactly the same as Robin with the same results.
Don't be afraid of the balance screws if you have a carbtune.

To be honest I thought I was missing something because although there are only three to contend with I had absolutely no trouble synching the Speed triple TB's when I put them back on. And as Rick G mentions, had I not re-plated the adjuster arms I could have left the original settings untouched.

I have been giving more thought to the switch to K1100 TB's so may try and find a decent set.

Thanks

Fent

I have done them before. Not difficult if you are methodical. Just make sure that you build up whilst continuously checking the free running of the operating parts. It is not difficult and much has been written about setting the TB plates. It won't be any more difficult than your previous job.

Fentible,

How did you clean the throttle bodies so well?  They look new.
Thanks,
Jim

You're correct, there is no dark secret - they're just throttle bodies.
That said, you'd need a carbtune to get things right again after disassembling them. The rest is just common sense.
Most problems with 'unbalanceable' throttles are eventually traced to a lack of sealant on the cylinder head adaptors after a strip down.

 A tip: some of the thin nuts that retain the quadrant/linkage arms onto the butterfly shafts are left hand.

Has anyone completely disassembled the throttle bodies, to include the butterfly shafts, and successfully reassembled? If so, do the butterfly shafts have 0-ring seals?

I was talking with a mechanic at a BMW motorcycle dealership back in the late 1990s and he warned to never disassemble the throttle bodies, because he apparently was unsuccessful at getting the bike to run properly after he had totally disassembled them.

I've contacted Bing USA about K100 throttle body tech information, but for some reason, Bing Germany refuses to release any information pertaining to the early BMW K100 throttle bodies.

Bing will have been gagged by BMW I guess, that was their normal practice.
I've completely disassembled throttle bodies as you describe. It's not black magic - they're only carbs without jets.
Of course you can mess things up if you get it wrong, but that applies to lots of things.

No o-rings on the shafts.
Some of the thin nuts that retain the linkages are left hand thread.
The two butterfly retaining screws seem to be peined over to prevent them coming loose. A good fitting screwdriver and a bit of care sorts this out. Avoid bending the shafts by supporting them from behind with a dolly - this allows you to use a bit of pressure on the screwdriver.
Keep a note of which way round the butterflies fit and replace them the same way.
Reassemble by clamping all the throttle bodies lightly between two flat plates - I use a wide-jawed joinery vice. This keeps them in good alignment before you tighten the screws that mount them onto the frame.
Set the linkages initially by viewing the tiny crescents of daylight around the edges of the butterflies.


At all times take care when allowing the butterflies to 'wedge' in the throttle bores under spring pressure - something which is normally prevented by the throttle stop screw. This is unavoidable during disassembly/assembly, but it is a good way to damage things if not done carefully.

chris846 wrote:
No o-rings on the shafts.

Are there any seals on the butterfly shafts? The shafts appear pass completely through the throttle body housings. I would think that there is some type of seal to prevent air leakage.

Do you know of any pictures of this Throttle Body assembly completely disassembled?

Regards

I did a project on my bike where I replaced the K75 TBs with  K1100 TBs. I documented it here: https://k75retro.blogspot.com/2014/04/adapting-k1100-throttle-bodies.html.  I had to completely replace the butterfly shaft in TB4 meaning that I had to completely disassemble and reassemble it. I remember that there was at least one rubber washer that sealed the shaft and prevent leakage on the TPS side. There was no rubber washer on the other end; just sealing metal washers. The picture of the two TB shafts on that page shows the washer. This was a number of years back when I did this and my recollection may be inaccurate.

I'll double check. I would've replaced simple o-rings had there been any, especially seeing as leaks will easily screw up the running.

FYI - The link below is a YouTube guy that's rebuilding his K100. Since it appears that he rebuilt his throttle bodies, I posted a question asking about o-rings on the butterfly shafts. He indicated that there are o-rings on the shafts, but I don't see it featured in any of his videos.

https://www.youtube.com/watch?v=YbArWV4PLfw&lc=UgxiWWX6Gw2KphP4jKR4AaABAg.9KRwKsencJN9KSoehFt9dd

I also sent an email to Bing USA asking about rebuild kits for the Bing Type 95 Throttle body. I expect the same "no" answer I got several years ago. I think my BMW K100RS has the Bing Type 95/34/401 Throttle Body assembly. As chris846 indicated, there must be a BMW gag order on early K100 throttle bodies, because Bing Germany refused to provide Bing USA any information. It was my impression that Bing USA made an honest attempt to get some information.

The throttle body butterfly shafts do wear out, and Bing USA has rebuild kits and parts for the Type 75 throttle bodies. See the links below.

https://bingcarburetor.com/uploads/9/8/7/9/98794296/throttle_body_wear_sample.pdf

https://bingcarburetor.com/uploads/9/8/7/9/98794296/throttle_body_rebuild_parts___prices_2021.pdf

Apologies, there aren't any o-rings, but there are lip seals. After removing the shaft, this was left in the bore.



The one on the other side came away with the shaft:


The 11mm AF nut was RH on this body, but on others it can be LH


And finally, here's a tip for aligning things on reassembly:

chris846 wrote:Apologies, there aren't any o-rings, but there are lip seals. After removing the shaft, this was left in the bore.



The one on the other side came away with the shaft:


The 11mm AF nut was RH on this body, but on others it can be LH


And finally, here's a tip for aligning things on reassembly:

Is there a source for those lip seals?

Who is the Bing supplier in the UK?

Mate, an hour ago I'd forgotten they existed.
I'll measure one for you 

Bore/shaft size is 8mm
Nominal OD/Bore in throttle body is 13mm
Thickness/height of seal 2.75mm

The seal seems to have a plain bore (i.e. not a lip seal) and a parachute outer that makes it a light press fit into the bore.

And
I've no idea who the bing supplier is in the UK. But I have a mate who can fix you up with a nice bong 

chris846 wrote:Bore/shaft size is 8mm
Nominal OD/Bore in throttle body is 13mm
Thickness/height of seal 2.75mm

The seal seems to have a plain bore (i.e. not a lip seal) and a parachute outer that makes it a light press fit into the bore.

This is the first, probably the best picture of a Bing Type 95 Throttle Body butterfly shaft seal I've seen on the internet.

Question is; is it a standard type of seal (i.e cheap, available) or a bing thing (i.e. well, you get it)?

chris846 wrote:Question is; is it a standard type of seal (i.e cheap, available) or a bing thing (i.e. well, you get it)?

I'm looking in to it. I called Bing USA and asked about Bing Type 95 parts. The Bing USA website indicates to call or email about Type 95 parts. They don't list rebuild kits for the Type 95 as they do for the Type 75. The guy said he would get back to me. I think there's a good possibility that it's a common part used on other Bing throttle bodies if the butterfly shafts have the same diameter.

I know they've contacted Bing Germany before, but they get no information.

Agree re. hoping that 8mm is a standard shaft diameter.
It's been said that BMW were behind the non-information policy that Bosch had with the Motronic etc.
And I know that BMW moved to Magura master cylinders because Brembo told them to do one, when they tried to prevent Brembo selling spares directly.

Are you sure they need replacing? Agree that it must seem good practice, but I've messed with these things and never had a problem with poor idling due to leaky shafts, nor am I aware of anyone else posting on this forum that they've had to do it?

Well, parts wear out eventually. See the Bing link I posted above. That's why they sell rebuild kits. Unfortunately, BMW K100 owners only have used eBay parts if they've got a worn throttle body assembly, because I believe K100 throttle bodies are discontinued, or NA from BMW Motorrad.

I haven't seen any information anywhere about a full rebuild of the K100 Bing 95/34/401. If the butterfly shafts are all standard diameter, then seals and bearings from other 8mm shaft diameter models may fit. It would be good to know.

That leaves only shafts and springs to source. If it came to it, I could make a shaft, because I have a metal lathe. I could make the bearings and springs as well, but I rather have a source.

As for leaking butterfly shaft seals, I don't know that anyone has really tested for leaks. How much play is excessive? It would take a special rig to test for shaft seal leaks. What's acceptable, and what's a no-go? I suspect that the mixture adjustments can accommodate some degree of leak. Most of these K100s are at least 30 years old.

Well if the shafts are leaking, it'd manifest itself as a poor idle long before it could ever get to the stage where it'd affect actual part-throttle running.
There's been a fair few threads on here about bikes with poor idling. Most of them end up with the OP sealing the adaptors down onto the cylinder head with gloop. Or, replacing a leaking crankcase breather hose. This happens once they tear their attention away from those tempting-looking twiddly screws. I'm not aware of anyone reaching the stage where they just cannot get things to balance and it turned out to be worn shafts or seals.
Of course I'm not saying the shafts and seals don't wear, but rather I agree with your suggestion that the idle air bypass screws are probably capable of balancing out any shaft leakage. That is, after all, part of their job. It follows (at least in my logic) that so long as things can be balanced up with the bypass screws, then whatever is or isn't leaking down the shafts just isn't a problem. Further to that, leaks of that order only count when vaccuum is highest and airflow is lowest i.e at tickover. Once the butterflies are open just the tiniest bit, those leaks become inconsequential.

Charlie @ Bing USA wrote:The only parts we have for your throttle bodies are the black rubber seal for the shafts, and there is a plastic bushing, I’m not sure where it goes. About 19mm od.

The quote above is the first email response I received from Bing USA. It's not entirely bad news.

Does anyone know where the 19mm OD plastic bushing goes?

I responded with a few additional questions. Hopefully we'll get some more useful information on available parts for the K100 throttle bodies.

Inside the spring.

Can you post some pictures?

Yes, but you can easily see it inside the coiled return spring on the side of the throttle body, around the shaft. It's just a white plastic bush to prevent the spring wearing against the throttle body.

Well, I wanted a pic if available to send to Charlie @ Bing to confirm we are talking about the same thing.

I'd do it myself if I was near my bike, but I'm on the road for awhile.

I sent him that picture of the 8mm shaft seal for a confirmation. I haven't heard back yet.

I'll send one tomorrow a.m. Currently pulled stumps and sat in pub down garden...without USB cable for pics. Soz!

Edit: sorry, stumps are those stick things that we english throw balls at in the game of cricket. Pulling them (out of the ground) is what we do when we've wrapped up for the day.

Edi2t: 'wrapping up' is what we english use to describe the final stage of any process...oh you get it!

Edit3: The Aussies know what pulling stumps means too: we taught them cricket when they were still in prison!

Here y'go:

Thanks, those are good pics.

OK, I called Charlie again at Bing USA and he provided some additional information.

He indicated that the butterfly shaft, 8mm diameter, bearings/bushings are common to other types that they sell. He indicated that the bearings/bushings come in two lengths. They could be made to fit the Type 95/34/401 throttle body housings if they were equal or greater length than the K100's. He also indicated that the butterfly screws are likely common parts as well. The return springs may be common parts also. He would need good pictures and dimensions to attempt to match to known stock parts.

Since Bing Germany almost certainly has a confidentially agreement with BMW to not disclose technical information, Bing USA has no information about K100 throttle body assembly's component part numbers.

If anyone has a K100 throttle body assembly disassembled and can post good pics with measurements, I think it's possible to construct a nearly complete rebuild kit part number list.

I already slightly stripped the end of shaft nut by attempting to loosen by turning left.  I want to ensure I understand the butterfly to shaft screws correctly.  Counterclockwise to remove?  Correct?  Any tips?  Should I try to remove bent over threads?
Thanks,
Jim

You might get lucky getting a replacement nut from Bing USA. Charlie might be able to answer your question about the threads. If no luck with Bing USA, you will likely get lucky on eBay finding a throttle body you can cannibalize. You should post a pic so we can see what you're seeing.

"I want to ensure I understand the butterfly to shaft screws correctly"


I think you are referring to the two small slotted screws that clamp the butterfly/throttle plate into the slotted brass throttle shaft.


If so, I've found the best way to remove them is to get a good fitting screwdriver - grind one up if necessary - and use plenty of pressure to stop it slipping. That sort of pressure might bend the shafts so, to avoid this, clamp a dolly (a piece of 1" bar or something) in the vice and use this to support the rear of the throttle shaft as you press down on it.


The screws are normal (RH) thread btw. The LH thread thing concerns the nuts that secure the linkages/cable quadrants to the throttle shaft on some of the throttles. 

During reassembly of the throttle bodies, do you recommend any lubricant to be used on the brass shafts?  I am thinking about a tiny bit of synthetic grease of some type. 
Thanks!!

https://bingcarburetor.com/index.html

Call the Bing Agency International. They offer technical assistance on throttle body rebuilds.

https://bingcarburetor.com/throttlebodies.html

Suzi Q wrote:Edit3: The Aussies know what pulling stumps means too: we taught them cricket when they were still in prison!

Then someone decided to burn the stumps to keep warm.  It gets a bit chilly in Port Arthur.  

When the guards came around, someone hid the ashes in an urn and as they say the rest is history..... 

Jumping in here as I have completely torn down my TB's and only after reading the posts realized that maybe that wasnt such a good idea.  Has anyone had any luck on a rebuild kit from Bing?