Hello all!

This is the start of my K100 "TT" build thread. 

Austin has been the host to two great events for the past several years: MotoGP at Circuit of the Americas and the Handbuilt show. After going to this year's show, I felt inspired to build a bike. In the past I've dabbled with cafe-racering my old Street Triple and built a race bike out of my Daytona 675R. For this project I wanted to start with something older, simpler, and less expensive. A bike that I could tear down, put back together, and modify to my hearts content. I thought about R-bikes and old Hondas, but they are getting harder to come by unmodified and/or for a reasonable price.

A month ago, I found a 1985 K100RT with 77k miles for a very reasonable price to use a the basis of my build. This bike had obviously been dropped on the right side, was missing some fairing pieces, no radio, etc. -- perfect for my purposes. I handed over the cash, and rode it home in a light rain, fairings shaking all the way home. I believe I'm the 5th owner (the 4th bought it to fix and flip it).

My concept for the build has evolved quite a bit during the past month as I've combed through Google search results, Pinterest boards, Bikeexif, and various Facebook groups. My starting point was a traditional cafe racer build - 7" bucket headlight, clip-ons, and curved seat hump. Something like this beautiful build:



As I explored more, I found some other projects that began to alter my course:



And then:



The question formed - "What would a K100 endurance race bike have looked like?" 

I printed out a bunch of images, cut out the fairings with old fashioned scissors, and began playing with the shapes of things.



I posted these photos on Facebook, and a friend of mine pointed me at http://www.airtech-streamlining.com/. I began to explore their vast inventory looking for an appropriate shape. Shortly thereafter I discovered the "Martin/Brune" fairing and "JJ Cobas" bike and build thread via this forum.

Welcome to the forum.

That sounds like a good bike to start with, as in the plastics are already KOd.

Check how the gas tank is fixed, is it bolted on or not. This will tell you if its the early or later one. This affects electrics and things like seats, gad tank and so on but it may not be an issue if you are doing away with  a lot of this stuff too.

A lot of threads about what you are proposing, let us know how far you are going with it.

Bear in mind you cannot bore the K engines, the use a Nikasil hardened bore which sort of lasts forever. But, the engines too also last forever. You can swap pistons from K75 as they are higher compression ratio but otherwise I don't think much you can do inside the engine but see how some of the guys have ported and polished the heads. The good thing is engines a plenty are out there. Check out threads on rivets, as in 6 rivet output shaft. If you are going inside the engine you should check this out and possibly replace with the later one. You can change around engine management systems as K100/K1100/K1200 have a degree of development that can be applied back to earlier K100- threads on these too.

You will enjoy this as some of the forum members have made some amazing Ks starting with what you have.

Don't be afraid to ask questions even if you think its nothing, everyone is very helpful and willing to share experience, thoughts and ideas.

Last week (prior to the discovery of the JJ Cobas K100R Flying Brick thead), I did a number of photoshop mockups based on different fairings from Airtech Streamlining. This is a composite of my top two concepts based on the Ducati F1 750 and the Suzuki XR69:



Based on the measurements of the F1 fairing (16" at widest point) and the fact that I would have to modify the radiator to make it work, I decided to go with the "TT" concept.

92KK 84WW Olaf wrote:Welcome to the forum.

That sounds like a good bike to start with, as in the plastics are already KOd.

Check how the gas tank is fixed, is it bolted on or not. This will tell you if its the early or later one. This affects electrics and things like seats, gad tank and so on but it may not be an issue if you are doing away with  a lot of this stuff too.

A lot of threads about what you are proposing, let us know how far you are going with it.

Bear in mind you cannot bore the K engines, the use a Nikasil hardened bore which sort of lasts forever. But, the engines too also last forever. You can swap pistons from K75 as they are higher compression ratio but otherwise I don't think much you can do inside the engine but see how some of the guys have ported and polished the heads. The good thing is engines a plenty are out there. Check out threads on rivets, as in 6 rivet output shaft. If you are going inside the engine you should check this out and possibly replace with the later one. You can change around engine management systems as K100/K1100/K1200 have a degree of development that can be applied back to earlier K100- threads on these too.

You will enjoy this as some of the forum members have made some amazing Ks starting with what you have.

Don't be afraid to ask questions even if you think its nothing, everyone is very helpful and willing to share experience, thoughts and ideas.

Thank you!

I'll start with the gas tank - it does not appear to be bolted down at all. What does that tell you about the bike?

For electronics, I've determined that my instrument cluster has flat pins - useful information for ordering a BEP 2.0 box to support an alternative cluster.

zroadhouse wrote:

The question formed - "What would a K100 endurance race bike have looked like?" 

 In endurance trim, the Cobas bike looked like this-obviously the belly pan is missing.
Note the low mounted deep triangular radiator that's only possible because the engine sat quite high in the frame. That allowed the forks to be much nearer the engine and gives a much shorter wheelbase.



Her's another version with a headlight in the fairing.



and here's the Airtech fairing I used on my XRtt.

Thank you!

I'll start with the gas tank - it does not appear to be bolted down at all. What does that tell you about the bike?

You probably should post up the VIN number but there were significant changes made in 85 and the bolted down tank is often the easiest way to alert anyone not too familiar with the K details.

Things that differ with this change are clocks [7 litre and 4 litre warning lights changed to a single 5 litre but now allowed for a fuel gauge], clock connector wiring, fuel pump tank to wiring loom connections, seat, rear ducktail, exhaust, side panels [?], footrest hangers to name but a few. I have 84RT and 92LT both have 8 valve engines and lots of parts that don't swap from one to the other. Drive shaft changed from 16 to 20 spline so not interchangeable unless you change final drive as well. But you can buy ends and get them welded on.

This may be much less relevant if you are making bigger changes.

You can change the rear end from the 8 valve Monolever to the 16 valve Paralever. You can even put a 6 speed K1200 gear box in BUT you need expertise to modify the frame because the gearbox support points differ due to the frame design change that came with the introduction of the K1200.

Fork diameters changed at some point too, so be careful. I don't have the exact details but then you might instead be putting on a K1100 front end which is a popular upgrade.

Its really a case of how big is the imagination, how much of the expertise is your own and therefore free.

VIN is WB1051409F0052993

Instrument cluster has 7/4 liter warning lights on it. Sounds like I have the earlier model.

Some info from the Bimmer.Work site on your machine.

Vehicle Identification Number	WB1051409F0052993
Type	0514
Model	K100rt - USA
Development Code	K589
Engine	4-ZYL
Displacement	1.00
Power	66
Transmission	MECH
Color	Bajared Metallic - 578
Upholstery	Nicht Gemeldet - *
Production Date	1985-03-01

If the tank isn't secured at the back by a single bolt, its most likely the later tank which only had the sender for the single light. (Look for 2 thick pins downwards from the back corners of the tank which engage with little brackets on the frame rails.) Perhaps the instrument cluster has been changed during its life? Shouldn't make any difference to the operation, except that only the 4L labelled light will work, and with the later sender its actually a nominal 5L light.

Looks to be an interesting project.

Bill

Took a few pics (sorry they are rotated wrong - happened on upload). Perhaps I'm just missing the bracket for the tank to bolt to?

Or perhaps the fuel tank is not original? I can see in the factory manual where the fuel tank prongs should insert into the frame.

EDIT: I also found this diagram showing the older version of the tank. Looks like I'm just missing the bracket.

K-bike getting naked.

zroadhouse wrote:K-bike getting naked.

Poor thing sitting out on the porch in public with nuthin on

zroadhouse wrote:Or perhaps the fuel tank is not original? I can see in the factory manual where the fuel tank prongs should insert into the frame.

You have the older tank as well as the older instrument cluster, so a good chance they are both original. Final check would be if the wiring to the fuel light sender looks original. 

Someone with more knowledge would be able to say when they changed in the USA market, which may not be the same as other markets.  

Bill

indian036 wrote:

zroadhouse wrote:Or perhaps the fuel tank is not original? I can see in the factory manual where the fuel tank prongs should insert into the frame.

You have the older tank as well as the older instrument cluster, so a good chance they are both original. Final check would be if the wiring to the fuel light sender looks original. 

Someone with more knowledge would be able to say when they changed in the USA market, which may not be the same as other markets.  

Bill

On the original tank the electrical connection is at the front left of the tank, tank is bolted down. This has a 7 litre orange and 4 litre fuel red warning lights in the speedo side of the clocks.

The later tank has the electrical connection at the rear right and the tank has the two prongs inserted into the frame. This has a 5 litre red warning in the speedo side of the clocks.

The clocks are not interchangeable due to different connector plugs.

92KK 84WW Olaf wrote:The clocks are not interchangeable due to different connector plugs.

Not having occasion to play with earlier clocks, I wasn't aware of the connector difference. (My '84 came sans clocks.) Familiar with the other differences. 

Thanks for the enlightenment, Olaf. 

Bill

92KK 84WW Olaf wrote:On the original tank the electrical connection is at the front left of the tank, tank is bolted down. This has a 7 litre orange and 4 litre fuel red warning lights in the speedo side of the clocks.

This is what I have - wiring connection is front left of the tank. Good to know the tank is original!

Helps when I have both Ks to look at......seeds of an idea are slowly coming together too.

And my RS looks just like that naked bike on the porch except no handlebars and no tank...

I've surveyed various threads on this forum and in a few other locations for information on maintenance and performance work that I should do.

Here's my current plan:

• Perform 12/24k maint (fluids and plugs) using this kit from Beemer Boneyard
  
• Inspect and lube the final drive splines
  
• Replace the clutch cable and barrel
  
• Inspect/replace the clutch plates? (probably required given the 77k miles on the bike)
  
• Send away the fuel injectors for cleaning
  
• New spark plug wires?
  
• New thicker battery cables?
  
• Advance timing 4 degrees
  
• New exhaust -> BSK 4-1 collector plus a slip-on TBD
  
• Extend intake snorkel to inlets on the fairing
  
• Balance throttle bodies
  
• Replace corroded fasteners
  
• Clean engine covers, etc.
  
• Inspect the brake system, potentially rebuild, replace pads, etc.
  
• Send suspension to my suspension guy for service/rebuild (bike has an aftermarket shock - not sure about the fork internals)
  
• Modify the frame
  
• Powdercoating
  
• Bodywork
  
• Paint!
  

The teardown is almost done. I picked up a motorcycle lift from Harbor Freight. It makes working on the bike a pleasure compared to kneeling on the porch all the time.

I found a worn and cracked rear disc and some evidence that a prior owner had tried to change the oil with the wrong tool. I ordered and received a fresh EBC disc and pads. I fixed the oil pan by grinding and honing the imperfections down.

Rear drive splines were bone dry. There was some wear on the male side. Moly-lubed and reassembled.

I built up a wooden block to support the engine. Seems to be doing the trick.

Fairings came in on Sunday! These are the F1F (XR69) and MORI2 fairings from Airtech Streamlining.

Trial fitting the upper and tail seems like they will work just fine. I haven't tried the lowers yet.

Looks really good! Can't wait to see this build progress   I'm looking to change my seat up in the future so this is great inspiration