Hello, everyone!

I just picked up this wrecked  ‘85 K100RS from an auction house as a project with the aim of fixing it up in the next year or so. I never touched an old BMW before, but have admired them from afar. The idea is that this will force me to learn more about the bike with minimal initial investment. The major damage is to the front end, and I the frame is bent, along some minor damage. This leads me to my first few questions:

- Get new frame or get the original one straightened? Do all K100 frames fit each other? Is there a list somewhere of part compatibility?
- A bunch of the bolts are rusted and need to be replaced. Does anyone sell sets of stainless steel K100 bolts?

Looking forward to be a part of this community.

Alex

Hi Alex,

Used frames aren’t much money, at least not from MotorWorks. You’ll want to get a shipping quote before proceeding but I can’t imagine you’re going to get that frame straightened (IF it can be straightened) for less than the cost of a used frame, shipping excluded of course.

https://www.motorworks.co.uk/vlive/Shop/Parts.php?T=5&NU=10&M=40&Ct=OA&SbCt=BA_10_40_OA_10

Stainless steel fastener sets are also available from MotorWorks-not cheap. The original fasteners are cadmium plated I believe, so perhaps an alternative is to try and source a used set of original fasteners.

https://www.motorworks.co.uk/vlive/Shop/Parts.php?T=5&NU=15&M=40&Ct=YM&SbCt=BA_15_40_YM_50

I’ve never taken on such a project but I should think prudence is well justified here. Get the bike apart, then see what you need and the costs involved before spending any money. There could be more damage not visible to the eye until you get the bike apart. The good news is there are lots of new parts and used parts still available with some time searching the internet required.

Your mileage may vary and there are others who will certainly know more than me. Just a couple of thoughts of mine and pointing you to where you can get some stuff you might need.

RS Rider wrote:Hi Alex,

Used frames aren’t much money, at least not from MotorWorks. You’ll want to get a shipping quote before proceeding but I can’t imagine you’re going to get that frame straightened (IF it can be straightened) for less than the cost of a used frame, shipping excluded of course.

https://www.motorworks.co.uk/vlive/Shop/Parts.php?T=5&NU=10&M=40&Ct=OA&SbCt=BA_10_40_OA_10

https://www.motorworks.co.uk/vlive/Shop/Parts.php?T=5&NU=15&M=40&Ct=YM&SbCt=BA_15_40_YM_50

Thank you, RS Rider! These are very expensive bolts, indeed, more than I paid for the whole bike, so that would be an extravagant purchase at this stage. At least the frames are cheap. I agree with the strategy — I don’t want to spend anything else until I figure out the extent of the damage, mainly whether the motor and drive work, and whether I can rebuild the bike or just to salvage parts.

I don't know about Oz, but here, even if you are able to straighten the frame(very doubtful) the bike will have a salvage title which will lower it's value to almost zero regardless of it's condition.  It would be much better to locate a straight frame with a clean title and transfer the rest of the bike to it.  That is the route I took several years ago, and it worked out pretty well.

Put some chicken wire around that frame and use it for a crab-pot. Do you intend to restore it to original or the updated butchered cafe racer thing that it was made into.
If you intend original get a straight bike and use that one for spares.
The only difference in frames is the RS and RT versions had rubber mounts in the front down tubes to prevent the plastic bits suffering from vibrations.
Ask the Aussie members if they have a frame.
As for the stainless bolts take the originals to a bolt specialist and get replacements in stainless, that price from motorworks is outrageous.

In Oz, if the vehicle is more than 15 years old it doesn’t go on the written off register for some reason, so a frame swap should be easy since all of them are at least that old. I’ll have to get a license, a boat, and I can start crabbing with the old one. The frames are compatible between years?

I still haven’t decided the final look for the bike, since my initial goal is to get it running and learn more about about how it works, and then to see where my mood takes me. The cafe racer appealed to me because all of the innards are exposed, and there just happened to one getting salvaged for not too much money.

Hi mate, welcome! Whereabouts in Sydney are you?

You’ll find a lot of good info/people here that can help you with technical questions. I’m close to Cronulla and happy to help with a bit of info

Cheers and Happy New Year, Rene

Thank you, Rene! I’d love to get to know people with knowledge. I’m in North Sydney, but travel a lot (going to Wollongong and Canberra weekly to see family) so pretty mobile.

Welcome Alex

Hi Alex

you could try Graham at https://kmodelbeamerbits.com.au/, he has not finished adding all of his parts to the page so give him a call.

Cheers Jamie

Thank you for the great advice! I managed to find a very reasonably priced frame and front fork assembly, so now I can go through and start checking the rest. The handlebar controls are badly damaged, and this pet scares me a bit. Given that most of the original electronics have already been stripped out, it doesn’t seem to make sense to install OEM switches. The fact that the ones I have are damaged makes it a bit more difficult to figure out how the wiring should be connected. I found a few older posts on people doing cafe racer mods that suggest that it’s not super easy. Does anyone have ideas about how to replace the controls?

FinalDrive wrote: Does anyone have ideas about how to replace the controls?

You could read this post and if you can't see the images, you could look at this post to get some ideas about what you read.

Thanks, Laitch! I found the first post, which bewildered me, but not the second, which is much clearer due to the pictures.

Original post edited to add clickable links to the pictures. They show up in post preview mode, but not when posted for some odd reason.

Since then I've changed LFB's switches to ones that came off a Triumph Sprint (left side) and Triumph Daytona (right side) because the Sprint switch has an integral choke lever. The downside of that game is having to make your own fast-idle cable to fit.

Yes , rewiring sounds daunting but its not really when you get your head around it . basically there are 2 ICU units . one goes direct to  fuel injection rail , the other links into that and sends the firing signal , you need to keep everything connected to those two harnesses along with the fuel injector relay and the ignition relay . it is possible to throw away all else and build a new harness for all the other electrics . There are electrical adapters that do away with all the other relays , Axel Joost and Motogadget are the ones i know of . This youtube contributor  -The illestrator - shows a good example of using the Motogadget unit and rewiring in general . He is no auto electrician though , lol

If you want to replace the forks with USD forks then Jax Garage in Melbourne sell conversion kits to fit the forks and you can even retain the original front wheel with a hub kit . they have a web site , they also built a k75 that featured in a number of publications , worth checking out .

Couple of Australian sites for buy parts for BMW cafe builds should you go that way , Rogue Motorcycles in Perth , Jax Garage in Melbourne , Purpose Built Moto in Queensland

For inspiration and ideas or simply to admire some amazing bikes subscribe to Racer TV on youtube .

Hey mate! 

I have a near complete 1990 K75S here not sure if it can be helpful to you with all the triple clamps and forks etc. 
Someone here more knowledgeable may be able to help with this info

Does anyone know whether hand controls from a 1990 K75S work on a 85 K100RS? I would love to do a straight swap if possible to start with.

FinalDrive wrote:Does anyone know whether hand controls from a 1990 K75S work on a 85 K100RS? I would love to do a straight swap if possible to start with.

No reason why they shouldnt work.  Later 16v (1000cc and 1100cc) are wired different, they should be avoided.

Al

The controls and connectors for the 2V are all the same, same counts for the 4V models.

Seems you have the old frame, and wiring.

For the wiring diagram get this; https://mega.nz/file/CugwmYoS#CZZ2zfD6piZ_aFlfwDRdQUPFtElpSE2OkFNzaAkKoDo