Hi all,

The actual question - Has anyone done this themselves? I'm mostly baffled by the K1100's front brake master cylinder and throttle pulling assembly, which is so different from an 8v K100 that nothing is interchangeable. Apparently I need an 1100 throttle tube and grip to go with the 1100 m/c, this is fine but my original grips are heated and I'd like to keep them. Looking around it seems the 1100 tube is longer and this is why 1100 grips are needed, am I correct? Could I not just cut the tube down and fit my earlier grips? According to this most excellent post I'll also need the indicator switch, which I can understand. Am I missing anything else?

The background, for those wondering - My K100RS has badly scored stanchions and probably incorrect fork springs, I'm still trying to get the cap off the top of the forks to have a look (I'm sure some of you will understand this!). To remedy this is around £200, and it still leaves me with the rubbish front brakes. I have found a man willing to sell me a K1100LT front including wheel/discs/forks/yokes/mudguard/axle/ABS sensor (if it can be made to work on the original system??) and one caliper (d'oh) for £200 plus whatever a courier demands. The draw of Marzocchi cartridge forks and 4 pot calipers is strong, and I can sell the old ABS discs and the rare 3 spoke K100 8v front wheel and possibly end up in profit. I understand that I'll probably need some bits of brake line making up but the hardest bit by far is the fitting the later master cylinder and throttle malarkey.. Has anyone done this? Would it be worth the hassle? Reviews of the K1100 at launch talk about how much better the forks were than earlier efforts, but people don't seem to be falling over themselves for these bits nowadays. And yet, to me it looks like an obvious way to go.

Thanks for any help/opinions/pointers!

Snod Blatter wrote:Hi all,

The actual question - Has anyone done this themselves? I'm mostly baffled by the K1100's front brake master cylinder and throttle pulling assembly, which is so different from an 8v K100 that nothing is interchangeable. Apparently I need an 1100 throttle tube and grip to go with the 1100 m/c, this is fine but my original grips are heated and I'd like to keep them. Looking around it seems the 1100 tube is longer and this is why 1100 grips are needed, am I correct? Could I not just cut the tube down and fit my earlier grips? According to this most excellent post I'll also need the indicator switch, which I can understand. Am I missing anything else?

The background, for those wondering - My K100RS has badly scored stanchions and probably incorrect fork springs, I'm still trying to get the cap off the top of the forks to have a look (I'm sure some of you will understand this!). To remedy this is around £200, and it still leaves me with the rubbish front brakes. I have found a man willing to sell me a K1100LT front including wheel/discs/forks/yokes/mudguard/axle/ABS sensor (if it can be made to work on the original system??) and one caliper (d'oh) for £200 plus whatever a courier demands. The draw of Marzocchi cartridge forks and 4 pot calipers is strong, and I can sell the old ABS discs and the rare 3 spoke K100 8v front wheel and possibly end up in profit. I understand that I'll probably need some bits of brake line making up but the hardest bit by far is the fitting the later master cylinder and throttle malarkey.. Has anyone done this? Would it be worth the hassle? Reviews of the K1100 at launch talk about how much better the forks were than earlier efforts, but people don't seem to be falling over themselves for these bits nowadays. And yet, to me it looks like an obvious way to go.

Thanks for any help/opinions/pointers!

My K75 Frankenbrick has a K1100 front end.  You need to swap EVERYTHING:

Forks
Fork trees
Fork brace
Wheel
Rotors
Calipers
Axle
Master cylinder

The grips are the same width but the throttle tubes are very different so you won't be able to use the original K100 one.  A K1100RS throttle cable will work but you need to bend the bar on the TBs down a few degrees to make things work properly.

You can run aftermarket heated grips with the OEM switch for <$50.

Ahhh someone who has done it, excellent. I understand I need to swap everything, I have found a man who is willing to supply me with almost everything so the actual spannering is hopefully not a problem, I've done steering head bearings and brakes before but only on Japanese machines. It's just the fiddly hooking-things-up bit that I'm beginning to not like the look of.

How different are the throttle tubes? Are they not just a pipe along where the grips go on? This is probably one of those things that'll make complete sense if I was looking at them in person, of course, but all the tubes I've ever seen before are all just a plain hollow plastic tube until you get to the business end that moves the cable.

Since you have done it, would you say it's worthwhile?

Before you bolt up a complete K1100RS front end to an 8V K100, lay the fork assemblies down on the ground next to each other and note the significant offset difference. The K11 front end will 'quicken' the steering substantially. One way BMW compensated for this was to include the Paralever rear end at the same time in production, which is about 50mm longer than the Monolever. Another thing done was to add a hydraulic steering damper. An answer is to have the K100 8V triple tree holes bored to accommodate the larger tube diametre of the Marzoc. forks.

The 35mm K11 TB swap, which includes the 20mm master cylinder, throttle tube and accelerator cable, is more easily done than you'd think upon first look. Refer to the lengthy 'K1100 throttle bodies on a K100' post.

Worthwhile? To me, yes.   But I built the bike from scratch.   You get much better brakes and better suspension. (K11 forks have progressive springs from the factory.)

The throttle tubes are VERY different.  The K1100 one pulls directly on the cable while the K100 has teeth that turn a gear.

The K100RS4V had a steering damper but the K1100s (which have the same front end) don't.  IMO it's just dead weight.

The early iterations of my K75F had a K11 front and mono rear end.  It rode fine that way but I found the monolever jacking effect annoying which is why I swapped in a paralever.

That is interesting, I wouldn't mind quicker steering at all! Mr duck, have you experienced any head shaking or the like? Also I'm looking to fit a K1100LT wheel to keep the front 18", I much prefer this to 17" which falls into holes, follows road imperfections and all that and the tyres are a bit cheaper  . If I had the yokes bored out would the forks still be the correct distance apart for the wheel/spacers?

I don't fancy the larger throttle bodies to be honest, the engine is already so far ahead of the rest of the machine having even more power to control seems a silly way to go!

I understand that the throttle tubes are different, but what about just the tube part with a grip on it, are these different diameters? Seems unlikely.

I am not fussed about the rear jacking itself up, as a problem it's much further down the list than ineffective brakes and forks!

Thanks all so far, there'll be many more questions yet 

I performed the conversion that you referenced in your first post.  I had that bike on the road with those forks (and the original brakes) for 15 years before I converted the brakes to 4-pot K1100 ones in 2010.  I continued to ride the bike with the new setup until last year.  In all that time, I never had head shake or any other form of instability at speed.  This K!00 also had the standard K100 rear end.

I have since transferred the entire front end of the K100 to my new K75 as part of a restoration/customization job I am undertaking.  Duck will concur that low speed handling (<20 kph) will be more twitchy than a stock K75 steering setup because of the LACK OF the steering dampening system.  When you swap out the old triple clamp from the K75, the Fluidbloc dampening will go as well.  You notice steering sensitivity at parking lot speeds but this could probably be overcome by installing an aftermarket steering damper.  Mind you this applies only to the K75.  I never noticed low speed sensitivity on the K100.

As for the throttle, Duck is right that the K1100 throttle is directly connected to the cable whereas the K100/K75 throttles use a geared mechanism to impart movement in the cable.

I have seen cafe-customizations on the Web where the builder has substituted a modern-day throttle and front MC.  This might be an option to investigate. With a radial MC, you can really dial in the brake feel.  The throttle mechanism will most likely be sized for a 78" bar, meaning you'll have more space between the bar and throttle tube.  The grip / heater options will be vast.  

The important factor for the brake conversion is the size of the front MC.  It needs to be AT LEAST 15mm.  The K100 is 13mm, the k1100 is 20mm.  The BMW R100RT Mystic front MC is a 15mm MC being a hybrid of the K100 (wrt. the throttle actuating mechanism) and the K1100 (wrt. the MC size).  If you can find one of those, then you can directly use your heated grips and old style throttle cable. In addition, it will have enough MC capacity to actuate the pair of 4-pot Brembos without feeling soggy.  However, finding one of those throttle assemblies is the trick.  When is all said and done, you'll probably spend more on the Mystic solution than to use K1100 parts directly and ditch your old grips.  If you NEED the heated grips, take Duck's advice and use aftermarket grips and heater.  That's what I did.

Ah mr robmack, my man! I have read your post at least three times, each time it makes more sense. I have had a quick look for the Mystic master cylinder but it's a bit small (Motorworks reckon it's 15mm?) and there are no used ones I can find, only new priced at £155 so that isn't going to happen. Maybe if it was perfect, but even then probably not. I could do with finding a service to perhaps bore out the original but this doesn't exist, I guess it's too much of a liability.

The normal separate m/c and switchgear a la Japan is what I'm used to, but then it really starts to look like a hack job and surely I would have to replace the left side too so that I can operate both indicators? I'm not a fan of this weird BMW switchgear, operating the right indicator and cancelling can mess up my throttle control but I don't fancy chopping up (much) wiring either.

So, aside from needing different grips, will I also need the different indicator switch because it mounts differently? Or some other reason?

Yes, with total aftermarket equipment, electrics can be fun.  Three signal buttons will need to be fashioned; the standard Japanese signal switch won't play nicely with the BMW flasher unit.  You can forget the headlight on/off switch and wire the lights under the tank to come on with the ignition switch.  The horn button will not be a problem as will the high beam switch.

You'll have some interesting challenges to solve if you choose that route.

Two Wheels Better wrote:Before you bolt up a complete K1100RS front end to an 8V K100, lay the fork assemblies down on the ground next to each other and note the significant offset difference. 

I didn't know there was a difference between K100/K1100 fork offset.  But what I want to add is that it's not only the forks that affect this.  
The offset that counts here to increase trail(slow steering, more stability) or reduce trail(quicken steering, better response) is the total offset between the steering head and the axle position, so the offset from the steering pivot to the fork holes in the triple clamps come in to play also.

Al

Last year I bought a K100LT, and one of the things I wanted to do with it was to replace the front end with that from an 1100.  However, after a little while I realised that there are so many other benefits from riding an 1100 that I'd be better off buying one.

Early this year I found a nice K1100LT, and although there are many similarities, there are also big improvements.  Of course, if you get your kicks from fettling bikes, then tweaking a K100 with later bits can be very satisfying.  Having said that you may decide, as I did, that it might be more fun to begin with an 1100 and then improve that. 

Whatever you decide to do with your K, I wish you lots of fun, and good luck.

Snod Blatter wrote: Also I'm looking to fit a K1100LT wheel to keep the front 18",

I have a pair of K1100LT wheels sitting gathering dust. The tyre on the front is shagged but the rear is very good, bags of life in it.

Arrange collection and they're yours.

Snod Blatter wrote:That is interesting, I wouldn't mind quicker steering at all! Mr duck, have you experienced any head shaking or the like? Also I'm looking to fit a K1100LT wheel to keep the front 18", I much prefer this to 17" which falls into holes, follows road imperfections and all that and the tyres are a bit cheaper  . If I had the yokes bored out would the forks still be the correct distance apart for the wheel/spacers?

I don't fancy the larger throttle bodies to be honest, the engine is already so far ahead of the rest of the machine having even more power to control seems a silly way to go!

I understand that the throttle tubes are different, but what about just the tube part with a grip on it, are these different diameters? Seems unlikely.

You'll need to use a K1100 tube as it's design is integral with the K11 front master cyl.

No head shake.   The only issue I noticed was that at uber low speeds (stop-n-go in a line at a stop sign for example) the front end was a little wobbly.  Not a big deal or dangerous in any way.  That went away though when I swapped in radial tires.

I've done a fair amount of local riding and took it up and down the CA coast last year and am very happy with the front end.

MikeP wrote:I have a pair of K1100LT wheels sitting gathering dust. The tyre on the front is shagged but the rear is very good, bags of life in it.

Arrange collection and they're yours.

That is very kind sir, but the front I am looking at buying already comes with an LT wheel. Are 1100LT wheels seriously unpopular?? I'll take an 18" cross ply over a 17" radial any day, but then I am an old fashioned handlebars rather than clip ons kind of guy.

I must admit, this is starting to look quite difficult. I am hoping to see quite a lot of Europe on this machine in May and the amount of fiddling about getting small things to fit and work is putting me off quite a lot, as it will almost certainly take longer than I am imagining - everything always does. If BMW had used separate master cylinders and throttle assemblies, this would be easy. If they had commissioned a wider range of master cylinders this would be easy. If my bike didn't have factory fitted heated grips that I don't want to cut up and rewire, this would be a bit easier. As it is, it's starting to look like a bit of a game.

By the way, does anyone have the faintest clue on whether an ABS-II (am I using the right jargon here?) ABS sensor could be fitted to an ABS-I system? I'd like to keep the ABS if I can, it's part of the eighties charm of the bike but swapping fronts means losing the original Hall sensor.

Many thanks to everyone so far by the way! 

And one thing I forgot about the K1100 front end that I discovered later is that the dash pad mounts get moved back and down when you install K11 fork trees.

I didn't discover this until I mounted a tank bag and rode to California last year.  With the tank bag on this made it awkward to get to the dash switches.

While in CA I did some custom bracket fiddling and moved the cluster back up to being right under the speedo where it belongs.

Before:



K11 ignition mounting cut off:



New bracket on rear fork clamp bolts:


Dash pad back where it should be:

I had seen that mentioned elsewhere, but the K100RS pad is a bit different, only having the two mounts near the tank (I think?) and the ignition switch is off to the left, like this:



I'm not even sure if that pad will fit the 1100 yoke at all, it might be something I would have to find out for myself or find a pad that would fit. Yet more complication!

You'll run into the exact same dash pad issue on a K100RS.

Been here, too.
I had just about all the bits to convert my K100LT to K1100RS wheels and realised that the more you looked, the more complicated it became.
Was about this time of the year, the sun came out and sold all the bits on eBay. Made a profit, too.
Might be a better idea if it's winter and, like our colonial cousins, there's a couple of feet of snow outside for a few months.
Or, it's not your only bike.
Or, buy another K as a project and get the one you already have on the road for the summer.

Those of you that have done it....

How did you deal with the massive big chunky ignition barrel of the K1100 front end protruding down and messing up mounting points etc for other items such as the fairing...


EDIT: Just cut off the K1100 ignition mount, and use the K100 switch block whcih also has the ignition mounted in it - Just as Rick said elsewhere. Couldnt visualise it though, and the penny has just dropped that the K100 has the ignition in the switch pad. Damn, I left the K100 switch pad else where....

Did you  see what I did with mine?  Sliced off the protrusion...



,,,and enlarged the hole to friction fit the switch.


It will screw-up using the dash pad though.

ahhh no I didnt see that. Thanks mate.

By "screw up with the pad" do you mean, wont work with the pad? Ie the pad would be in the way?

Right.  The pad will fit and all but it will cover the switch.

However, you can just mount the switch in the pad and ignore the K1100 ignition barrel hole all together.  That was the way my K100 was for 15 or more years.

Sorry to drag this up again...but I have seen several references (and different replies) to this: can you fit just the K1100 forks (without replacing the whole front end) on a K100RS straight swap (apart from break assembly) ?

Yes. But if I were you I'd stick with the 4V RS forks.  The K1100 forks aren't that much better and it''s MUCH easier to replace the fork seals on the earlier forks.

Ahh I remember this, it was just too much hassle in the end..

duck - aren't 4v and 1100 forks the same?? And the brakes for both are completely different to the 8v/K75? I get the feeling you're thinking of the K75 Showas..?

No. The early 4V Ks have different forks from the K1100s.  Same diameter and brakes but the fork internals are different.  The K1100s have the "dogs" in the fork caps that are a PITA to deal with. 



The early 4V Ks don't have those which makes it much easier to replace fork seals.

duck wrote:The K1100s have the "dogs" in the fork caps that are a PITA to deal with.

If the dogs are those four bind holes in the cap, wouldn't an adjustable pin spanner eliminate the pain?

The dogs are the semicircular parts. You have to pull up that rod in the center while depressing the two halves of the fork cap to get the dogs inserted properly.  It's a PITA.

I put K1 forks on a K75 last summer.  One was leaking. It was much simpler to replace that fork seal than it would be on K1100 forks.

ok, thanks for the reply...I was thinking of better brakes rather than maintenance, but fair point.

A 92 RS already has the same brakes as a K1100

Hi All, 
I've taken the front end off my 93 K1100 and already have the forks mounted on my 85 K100. I'll move the throttle bodies too for the improvement and to have the throttle and "cold start" cable match. 
What I haven't seen is anyone mention the wiring. 
I've diagramed out the electrical connections in this spreadsheet http://forum.kforum-tech.com/members-upload/uploads/k1100tok100Wiring2021.xlsx 
I figure things will work or they won't, but hoping others that have done this have some pointers.
Thinking I'll cut the control side cable on the K100 leaving a 5-8 inch tail to cut and wire in the control side cable from the K1100 so in the future I can disconnect the connecter if I need to.

UPDATE: 6/24/2022
This was easier than expected. The control "modules" on either side of the K100 (left: left turn, horn, hi beam. right: right turn, signal cancel and start) unclip after removing a retaining screw and clipped onto the new K1100 controls. For the ignition I un-soldered the K100 barrel and soldered those wires to the K1100 barrel. Wanted to use the K1100 key because I'm using the type 2 bags from the K1100 that share the same key. My K100 key is still used for the gas cap and seat lock. Lastly the hazard switch easily pops out of the K100 pad and onto the K1100 pad. I removed the windshield and abs switches from the K1100 pad and filled with blanks from the K100 pad. Finally, took the heated grips wiring harness off the K1100 and found the same connection on the K100 wiring loom. This allowed me to connect the heated grips switch and wires to the harness and everything works great. The only issue is mounting the lunchbox. Right now I have it rubber-bungied to the forks and have an aftermarket windshield that is keeping it nicely in place although tilted more forward then the original K100 mount.