K75s Two into One Project

[rbm]

Forks:  From Anton Largiader's web site, he's stating that the K75 were fitted with Fichtel and Sachs forks from 1985 onwards.  In 1990, the K75S model introduced the "S" forks; "S" forks will have an S stamped in the fork cap. "S" forks have damping valves in one leg only.  From 8/1991 through 1996, F&S were replaced with Showa.   Check the stanchion diameters; according to this table, there are two different diameters for F&S and Showa forks, 41.0mm and 41.3mm. 

Wiring: There is a different layout for the relay box on ABS equipped models.  The harness will have additional wiring to accommodate the ABS components.  But it should be beguine in your application.  Choose the harness that provides all the functionality you need and which is in the best condition.

ECU: Should be the same for both models.

[Scud]

Thanks for the wiring/ecu info. It sounds like I can either harness, which is good to know. It's kind of funny that many things from the older, higher mileage bike are slightly better condition - because it was garaged, while the other bike sat outside for a while.

Forks:
Thanks also for the fork info - I got a little confused and that table was very helpful. The differences are as you described. I saw the "S" stamped on the 1990 parts and I measured the difference in diameters.

If I keep the Showas, I have to tolerate a bit of pitting unless I can find a nice set of fork tubes. However, I might try filling the pits with superglue - I've heard of people doing that - then using super-fine wet sandpaper to smooth it off. The purpose of this is to make the fork seals last longer.

However, I have some steering head bearings to install and could swap the entire front end including triple clamps without much extra effort (although the 1990s leak and need to be rebuilt).

Is there any difference in performance/reliability between the 1990s Fiskel and Sachs vs the 1992s Showas? Is one fork considered better than the other?

[rbm]

The Showa has compression / rebound damping only in one leg (LHS).  I think the F&S has damping in both.

As they stand, neither fork looks to be better than the other.  Maybe consider buying and installing Racetech Gold Emulators for the one you choose to install.  That should allow for low and high speed damping control that is currently lacking in the damping rod design.

[Laitch]

The Showa has preload as well as compression / rebound damping only in one leg (LHS).  The other leg has just springing and preload.

I believe it's only the Sport forks that have left and right differing components. The Showa's should be the same in both tubes.

The Showas have a larger specified oil capacity than either of the others.

[Scud]

Thanks guys, for the fork discussion - gives me some more to think about.

Meanwhile, I totally disassembled the engine and some remaining sub-assemblies from the 1990 parts-bike today. The oil and water had mixed, and several bearings were not good. The worst bearing was the one in the cylinder block for the gear that drives the alternator - totally toasted and the engine case was severely blackened around the overheated bearing. This bearing seems to be rather weak in comparison to the rest of the engine - and you'd never know it was bad unless you removed the entire clutch housing.

However, the cylinder walls looked good, as did the main bearings and connecting rod bearings - after 180,000 miles.

I'm putting my Shinko rear tire on now and was second-guessing my choice of Y-spoke vs. 3-spoke wheels. So I decided to weigh the two rear wheels. Interestingly, the Y-spoke is nearly a full pound lighter than the 3-spoke. I expected the older wheel to be heavier.

1990 Y-spoke rear wheel weighs 10 lbs, 14 oz.
1992 3-spoke rear wheel weighs 11 lbs., 11 oz.

FYI - both wheels had no tire, but did have a valve stem and about the same amount of wheel balancing weights. For anyone who cares about unsprung weight, the older rims offer almost a 1 pound advantage, since I also like the looks of the y-spokes, I'm going to stick with those.

[rbm]

The source of my information:



Posted to K100-forum by Inge K. (I'm in no knowledge position to contradict him) :)

[Laitch]

That's a description of the Sport fork, true enough, Robert.

[Laitch]

Maybe in this post—http://www.motobrick.com/index.php/topic,7638.msg54673.html#msg54673—you were thinking "Sport" but wrote "Showa."

Anyway, Scud's moved on to wheels. You want to donate those three-spoke wheels to the Elderly Riders Association of Ridley Brook, Scud? If you do, you'll earn an attractive coffee mug with a handsome Dunkin Donuts logo for your generous contribution!

[Scud]

Dunkin' Donuts?  That's East Coast for sure... the only times I see DD is when I travel East.

I'll get around to listing some stuff for sale later (gotta pay for my play), but if you really do need some wheels (or anything else for that matter) let me know.

Here's a picture of that smoked bearing from the 180,000 mile engine. For orientation purposes, the bottom of the picture is the rear cylinder.

[Laitch]

Dunkin' Donuts?  That's East Coast for sure... the only times I see DD is when I travel East.

All the more reason to get yourself one of these attractive mugs now, before New England is underwater.

I don't really need these wheels, I just want spares for knobblies, i.e. not-quite-knobbies. I try to live by the adage, "I cried because I had no spare rims until I met a man who had no Hall Effect Sensor." I wouldn't mind knowing the price when they go on the block though.

[Scud]

Well, for some 50/50 street/dirt tires (or other ratio), you might be better off with the older Y-spokes. Lighter, stronger, cheaper.  8 attachments to the rim vs. 3 attachments for the newer wheels would be a real benefit if you think you might hit some rougher terrain.

[Laitch]

Those Y-spokes aren't going to be cheaper if you donate your three-spokes to me. :hehehe  Besides, the Y-spokes are too damn fancy for me and as far as their being stronger, I watch where I'm going most of the time and the rest of the time the three-spokes on my bike bash through the dirt road pothole fields just fine. Maybe the extra weight gives them some oomph. The spares would be for gravel road mud so I could skate faster in prolonged rainy spells, not for hill-climbing competitions.

[rbm]

Hi Scud:

Can you please do me a favour?  Since you have the triple clamp off the '90 K75S frame, can you measure some steering parts for me:

• length of pivot stem (from lower triple clamp to top)
• diameter of pivot stem
• length of steering head on frame
• bearing seat diameter on steering head on frame

I need these dimensions for a project I'm contemplating.  Thank you.

[Scud]

@RBM - here are the results from the 1990 parts.

Pivot Stem:
Length from top of lower triple clamp to top of threads:  176mm
Length from top of lower triple clamp to where tapering begins:  128mm
Diameter (to fit inside bearings):  28mm
Note that I ignored the portion of the steering stem that goes into the lower triple clamp

Frame:
Steering head length: 165mm
Steering bearing seat diameter:  52mm (BTW, this matches the outside diameter of the bearings I bought for the 1992)

Please also note that I used an analog caliper; it's possible that some rounding to the nearest mm occurred.

[Scud]

I've been going step by step to see how each change helps with my goal of eliminating some front brake pulsing. The new front tire reduced the pulsing a bit (the old one was cupped). I just put in some new front wheel bearings and while I was at it checked the steering head for play - there's none, so I was apparently a little over-zealous when I ordered the steering bearings.  After a short spin, I'm pleased to see that the pulsing is much reduced - to a barely perceptible level. However, next up are new EBC floating rotors and pads, along with caliper rebuild kits - this ought to totally eliminate the pulsing.

I also got some Spiegler stainless brake lines - but ran into a snag. I got them for the 1990 non-ABS setup, but apparently the PO of the 1990 replaced the original lines with some that go all the way to the calipers - and deleted the bent, metal brake tubes that go from the calipers to brackets on the forks. Called Beemer Boneyard, they do not sell used brake lines of any type, due to liability reasons - and they won't accidentally throw them away in my general direction either.  I asked...

I also put on a new Shinko rear tire. The bike is much more stable and predictable now. I like new tires.  :riding:

I've seen some complete front brake setups on eBay for a bit over $100 - but I already have 4 front brake rotors and would really rather not buy another set jus to get the metal tubes. I suppose I could try to find some same-length straight tubes and bend them myself... after I visit my friend who has my brake tubing bender...

Questions for today:

1)  How long do steering bearings tend to last?
2)  Related to Steering - does the 1992 bike come with the Fluid-block steering-damper? It feels like it has some resistance - this is new technology to me.
3)  Anybody have, or know where I can source, the metal brake lines that go from the calipers to the fork brackets?

[Martin]

Bearings last as long as bearings last, I got 140,000 Ks out of mine. It depends on lots of things, how you ride, do you do lots of wheelies , stoppies etc. Where you ride do you ride on lots of rough roads. And do you check and adjust them at regular intervals. I have a 92 K75 and it has a fluid block damper as far as I know all 75's  after 85 had a damper 100's did not. In order to check steering head bearing the two screws that go into damper must be backed off. When replacing the bearings be very careful to not damage the damper as they are no longer available. A special silicon grease is also needed available as Dow Corning High Vacuum Grease. There is plenty of information available on how to do it. Can't help with the brake lines.
Regards Martin

[Laitch]

2)  Related to Steering - does the 1992 bike come with the Fluid-block steering-damper? It feels like it has some resistance - this is new technology to me.

The fluid block damper is number 2 in this diagram. It should stand right out there, Scud. I think number 8 is a can of vanilla frosting.

[K1300S]

Frosting...LOL!

Hard brake lines. ..available new from bmw?  If not, simple to make.

[johnny]

greetings scud...

the hose man off the 5 and the 91... send your hoses so they can see the ends you need... then tell him how many of how long of each...

since you aints too far away id take them there... i know they can make them while you wait if you call in advance...

j o

[Scud]

Thanks for answering my questions while I am getting brick-acclimated. I didn't notice anything like that fluid block when I disassembled the 1990 - perhaps it was removed from that bike. I haven't had the forks or steering spindle off the 1992 yet, so now I know what I'm looking for. And being that we are in the Christmas season, frosting should be easy to obtain.

I'll get the last few inches of brake lines figured out. It was just a bummer to think I had all the parts ready to go and then to find out that I was missing something, especially because I spent a bit extra on the Spiegler lines, thinking that would "guarantee" an easy install...

My sad little story...  :musicboohoo:

Observation for the record: the wheel bearings on the Y-spokes and 3-spokes are not interchangeable. It's surprising how many differences there are between these two motorcycles. I guess BMW really took "continuous improvement" to heart in that era.

[johnny]

rodger that...

they finally got it right with the 1996 k1100 rs... the worlds most eloquent riding machine... since they couldnt make them better they just stopped making them all together...

j o

[Scud]

Here's a not-so-great picture of the flat-black powdercoated parts (they look even better in person). It cost me about $100 for the BMW parts (I had some stuff done for a Guzzi at the same time). It's so convenient to be able to still ride the 1992 K75s, while the parts from the 1990 get coated... FWIW, powdercoating is such a smooth, hard surface that the flat black has a bit of sheen to it - not at all like flat black rattle can paint - more like satin black rattle can.



I also bought a cheap front brake caliper from e-bay that had the hard line still attached. Painted the rear brake master cylinder with VHT's satin black brake caliper paint, which I will also use on all three calipers and the fork bottoms. I'm going to use VHT's satin black engine case paint for the remainder of the engine, tranny and driveline - and whatever other little bits need attention.

[Scud]

Wow - six weeks since I've done anything to the brick besides ride it and put gas in it.

Finally got around to putting on the first of my powdercoated bits - the fuel door. Too bad the tank paint has 180,000 miles on it (paint will be later). Hoping to get some wrench-time this weekend.

[Scud]

I've got the whole back-end apart, including the transmission off for spline lube. Doing ABS delete, and getting ready to paint and generally clean up before reassembly.

A few questions:

Swingarm bearings - all four bearings (two swingarms to choose from on reassembly) rotate well and do not feel notchy. However, they all have some lateral play - meaning I can move part of the bearing in and out a little. Is this normal? If so, I assume they snug up when on install from tightening the LH pivot pin - correct?

Clutch wear - is there any way to tell how much life is left in a clutch disc without removing it? Or a related question, about how many miles can I expect from a clutch disk? Bike has over 40,000 miles, clutch works well, but I don't mind replacing it while I'm in there if it's "about time" anyway.

Interchangeability of splines - as I determine the best-condition driveshaft and final drive, should I have any concern about mix/match - or try to keep parts together that were previously together>

[K1300S]

Clutch. ...5mm is approx new thickness iirc.   At 40k miles,  it should be good for a long time to come.