Currently rebuilding my K100, no real need, just seems I'm a lot happier when spannering a K-bike, oh well.
Anyway, I've had a set of K1100 throttles for some time now, with the intention of fitting them to the K100. I've got this forum-derived recollection that this modification doubles the horsepower, or something like that. Side by side the 'new' ones are a massive, oh, 1 millimeter or so wider than the the originals but I'm not dispirited, I still think it'll fly. Question is, does it make a difference and, more prosaically, what the hell do you do with the rearmost throttle that has an incompatible (Motronic) TPS? Is there a 'standard' way to get around this or shall I just let my troublesome imagination take charge?

BTW I fitted the lighter K1100 crank a while ago and that definitely improved things, there is some hope there. All replies, including 'just buy an 1100' and 'replace the large complex part attached to the number plate with the equivalent item from a Ducati', will be gratefully appreciated. Cheers.

I was just reading up on this so it is fresh in my mind.

I think this was the most informative post: https://www.k100-forum.com/t1944-k1100-throttle-bodies-on-a-k100

The gist being that the butterfly valve axle could be swapped to allow for the K100 TPS to mount "natively"
As well as swapping the mounting rails from the K100 to the new throttle bodies allowing for cabling to run correctly etc.

I have yet to begin my swap so the details aren't perfectly clear to me.



I had come across a couple posts of yours about using a lighter crank, so thank you for the clear wording here! It's something I am interesting in doing as well.

you might also like to change the throttle cable linkage on the no 3 tb between no 2 and 3 , and rear fitting bracket that holds the cable ?

If you're doing that Chris, you might want to add a vacuum manifold too (just sayin'). Eventually I blocked off the cyclonic separator stubs at the back of the TBs by linking 1-2 and 3-4 with small bits of tubing. Don't forget to advance the timing by 4 degrees too.

As Charlie says, watch out for the difference in cable mountings. I stuck with the K1100 and made a throttle cable to match.

Yes, it does make a difference. The assdyno says around 4bhp more in the midrange - that statement is based on the wisdom that you are unable to detect less than a 4bhp increase without a dyno. At the time I was in a position to run a back-to-back comparison with a totally bog-standard K100 vs the mods on LFB. No difference on the top end but a big fat additional punch in the midrange where it's really needed.

Anyway, why buy a K1100? It's much more fun making the smaller bikes do something stupid!

Suzi Q wrote:what the hell do you do with the rearmost throttle that has an incompatible (Motronic) TPS? Is there a 'standard' way to get around this or shall I just let my troublesome imagination take charge?

Don't look at this link, Suzi, if you want your imagination to run amok.

Thankyou for the replies, all useful.
Oddly enough, the set of K1100 throttles that I have, had already been switched over to the K100 throttle cable mounting bracket. At first, I didn't realise that this was the case, and as I compared the soon-to-be-replaced K100 throttles with their K1100 replacements I just thought "well this is all going to be extremely piss-easy, what's all the fuss about?". Then the lumbering swamp-monster that now serves as my memory came to life and I remembered that I'd previously nicked the K1100 throttle cable bracket for duty on my K75k project (the one with the exploding diy plenum chamber that got in the way of the OE K75/K100 throttle cable routing) Afterwards, I'd replaced the nicked bracket on the set of K1100 throttles with the redundant one from the K75 because, well, it just seemed the right thing to do, at the time. Hey-ho, serendipity. 

It'll be some time before I run the thing. This is because A: I'm dead slack, and B: the bike is a 1984 and my goal is to get it back on the road in time to celebrate its coming-of-age next year. Here in the United Republic of Kingdom and Camilla, when vehicles hit the 40 year mark, they undergo a magical, other-wordly transformation into never-aging, never unroadworthy, butterflies of the road and so there is no longer any need for annual MOT inspections, or even road tax. It's a bit like Carousel in Logan's Run ('cept that was thirty) and, yes, I'm now thinking of Jenny Agutter too 

Perhaps to keep some information consolidated here, and because I've just now done this myself.. here is what I decided upon to make this work easily.

1 - Swapped the K100 throttle cam, cable mount, idle stop to the K1100 assembly.
2 - Added a third return spring as is present on the K100. My throttles were not closing sufficiently with just two springs.
3 - Swapped the K100 butterfly valve shaft into the 4th position to allow for mounting the TPS without an adapter. Liberal application of vacuum grease and using the K100 spacer to close up the space in the K1100 exterior housing here.
4 - A small spacer was present on the fast idle switch, removed for K1100 to allow for proper engagement.

Other minor notes - the fast idle cable mount was bent on my donor throttle, making it difficult to get the guide threaded in place. I can see why this might happen with such a small amount of material there. I've yet to plug the larger vacuum ports on the back side. Could be an ideal tidy place to mount the lines from the sensor and fuel regulator.

Case1234 wrote: I've yet to plug the larger vacuum ports on the back side.

Those are not vacuum ports but they plug just as easily.

Just link 1 -> 2 and 3 -> 4 with two pieces of tube.

Just plug them 

7mm plugs fit .....from memory

chewing gum should do the trick.

The range of options can include tapping the stubs out M6 and putting grub screws in, with a bit of sealant. That makes it look like you've forgotten about blocking them up...

Attach flexible hose to them, pass the hoses between the throttle bodies so their openings face outward, then attach one of these to each hose for a dynamic style statement. Some perforation at the tips could be necessary so air pressure doesn't split them; however, the throttle passages will be protected when they coil at idle.

My favourite so far.

Now somebody beat that with a musical version...

Laitch wrote:Attach flexible hose to them, pass the hoses between the throttle bodies so their openings face outward, then attach one of these to each hose for a dynamic style statement. Some perforation at the tips could be necessary so air pressure doesn't split them; however, the throttle passages will be protected when they coil at idle.

Hello Laitch,

Could always fit individual. 'Kazoos' to each of them.

It would eliminate the possible splitting of paper.
 
Is that musical enough for you Suzi Q?
 
All the Best,
 
Rob54.

Glad somebody on the forum is making the effort with this...