BMW K bikes (Bricks)

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clappy

clappy
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I just built up a set of throttle bodies using k1100 TBs with the TPS shaft switched and k100 throttle cable stuff carried over to new.
It now seems like the choke mechanism doesn't have enough engagement to open the valves much at all. Way less than the K1 I compared to.
Is this a known thing with the swap?
Also, I swapped another shaft (forget why) and on both TBs where I switched the shaft the butterflies sit the same, but different than the other 2 (which also look the same). The untouched ones seem to seal perfectly and the 2 I touched have a bit more space when I hold them to the light. I tried changing the position of butterflies but still the same distance. they are now set so that all have the 10 print facing the same direction. How important is this if I am balancing them anyway?

https://i.servimg.com/u/f70/20/41/67/49/img_4910.jpg

    

robmack

robmack
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The choke problem is due to the cam follower being too far from the cam itself.  It's located near TB4 underneath the assembly.  Try searching as to why this space exists.  It might need adjustment of the cam to bring it closer to the follower.

There should be no light showing when the TB actuation shaft is at rest.  There is a procedure on this website (https://www.k100-forum.com/t1526-how-to-balance-the-throttle-bodies-solved) for adjusting the butterflies (if you were ever to touch the forbidden interlink screws) which involves using a drill bit between the butterfly and the TB cylinder wall.  I've also read of another similar process but using ball bearings instead of a drill bit.  You'll have to loosen the two brass screws securing the butterfly and fiddle with the spacing to get it right.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

clappy

clappy
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Thanks for the reply.
I'll keep trying to work out the choke.

For the butterfly adjustment, I'm not seeing a breakdown of the process on that thread or anywhere else online. Am I missing the explanation? I spent 2 hours trying to adjust the butterflies by hand so if there's a method I'll be happy!

    

Point-Seven-five

Point-Seven-five
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I can't tell you where to find the ball bearing procedure, but it's fairly simple.

Get some ball bearings approximately 3mm in diameter.  With the throttle bodies on the bench, put one one ball bearing in each throttle body with the throttle closed.  Then open them slowly.  When correctly synchronized, all the balls will drop at the same time.


__________________________________________________
Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

robmack

robmack
Life time member
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The gap in the cam / follower might be present because the butterfly shaft is not able to fully close. Check the screw that is on the stop (circled in RED below) to make sure it is not preventing the butterfly shaft from fully rotating.  The stop is between TB2 and TB3.  

Potential choke problem from k1100 throttle body swap K100-410


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

clappy

clappy
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So my TB setup is a mix of both k100 and k1100. Starting to think I missed something other than the 3rd spring not currently on.

So for the ball bearing procedure I still need to adjust the butterflies by hand but then check with balls? Does it help to loosen all and adjust together (I would like to leave the 2 I didn't touch, which seat well, if possible)?

Potential choke problem from k1100 throttle body swap Img_4911

Potential choke problem from k1100 throttle body swap Img_4912

    

Point-Seven-five

Point-Seven-five
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Are you saying that two of the throttle bodies are K100 and the other two are K1100?!


__________________________________________________
Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

clappy

clappy
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active member
No! I used the 1100 TBs and the 100 throttle cable stuff and TPS shaft. That's what I meant.
 I will try using the 1100 throttle cable parts and see if I can get the butterflies to seat better today.

    

clappy

clappy
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I realized I managed to strip 2 shafts. I think i'm just going to buy another 1100 throttle body set.
Other than altering throttle cable, I only need to swap the TPS shaft and add a few washers so TPS sits where it should, correct?

    

robmack

robmack
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That's right.  When I did mine, I was adapting a K1100 TB assembly onto a K75 engine so I needed to shed a TB.  Yours is a direct swap with changing TB4's shaft to adapt the TPS switch.  I assume you've read my blog page on my K1100 conversion.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

clappy

clappy
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Yes I have, thanks for posting that. 
I took a closer look and don't understand why people don't swap the throttle cable parts from the 100 over to not have to alter the cable. Seems you didn't either. Is there a reason?

    

robmack

robmack
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Life time member
Read the WHOLE story here:  https://www.k100-forum.com/t1223-installing-k1100-front-brakes-on-a-non-abs-k100rt

TL;DR:  I needed a k1100 bowden to fit the K1100 20mm Brembo front master cylinder which I needed to operate the dual 4-pot front Brembos.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

clappy

clappy
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Ahh, I had those 4 pots machined down to fit but bought a 15mm master thinking it would work. It did not, had very soft brake feel. My buddy now uses one of them on the front of his GSA.
Thanks for the info!

    

clappy

clappy
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Can Robmack or anyone confirm the proper order of washers for the TPS shaft?
From the blog post I understood it as: TPS,, circlip, metal washer from shaft, metal washer from shaft, 1.5mm washer, then the butterfly, and then rubber washer/seal on the other side.

Re-reading it I'm wondering if it should be: TPS, circlip, metal washer from shaft, 1.5mm metal washer, rubber washer, buitterfly, rubber washer.

I currently have 3 metal washers after the circlip, and just one rubber seal at the other side.

    

robmack

robmack
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clappy wrote:Re-reading it I'm wondering if it should be: TPS, circlip, metal washer from shaft, 1.5mm metal washer, rubber washer, buitterfly, rubber washer.
If you can stack the washers and rubber seal in this way and the shaft is free to rotate, then this is the best combination. The rubber parts being nearest the metal throttle body will work to prevent air leakage. The stacked washers are just to take up slack so that the circle can exert some pressure on the washers to seal up the gap. Give it a try.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

clappy

clappy
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Thanks, it seems to fit well. I also used the BBs to get a good baseline (will sync on bike later).

I may have stripped one shaft hole (it's tight but I didn't want to further tighten and fully strip it). The screw is sitting in there engaged and not going anywhere, just not as tight as the others.
I know this screw falling into the engine would be really, really bad, but do I need to be concerned about it getting dislodged when the bike is running? How much force could there actually be to push it out?

    

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