My K100 Cafe racer project story – Page 2


My K100 Cafe racer project story


Page 2 of 2

rbarrero on Fri Sep 09, 2011 3:34 am

First topic message reminder :

Hi all – I’m building a K100 cafe racer and i figured I would give back to the community by posting my progress with text and lots of pretty pictures. This is my story:

So I’ve been thinking about building a cafe racer ever since I laid my eyes on an old Ducati on the road a few years back and have always wanted a cafe racer bike since. I went to a Triumph/Ducati dealer in SoCal and test rode a Thruxton but it felt like a toy compared to the Ducati Monster I ended up buying. I tweaked the Monster and made it look like a cafe racer, but I still kept eying true cafe racers and waiting for the moment to be able to make the investment.

A year or two back I went to a bike show and came across a few BMW cafe racers and I absolutely loved them! The airheads truly make a great cafe bike, but still, I couldn’t afford it quite yet. Cafe Racer magazine also had some cool bikes, mostly Japanese, but so many ideas in it , so it became my monthly reminder to get a cafe bike.

I then one day I came across a K100 for sale on LA’s craigslist ( and I totally fell in love! After talking to the builder, he told me bits of his story and I was inspired. I couldn’t afford to buy his, but I never let go of the idea of making one.

Forward to two months ago when I laid down my Duc and the insurance totals it. Sad day, but my time was up and I healed my cuts and bruises. It’s funny how going down screws with your head, but I realized it was time to get back on the bike… the one I always wanted to build. I had to literally argue with the insurance to get the most for my investments on the duc, but it was totally worth it because I was already in the green on the loan and the payoff would be enough to buy a relatively cheap bike and also afford the customizations for the cafe build.

Like fate, a 1985 BMW K100 with only 4,500 miles showed up craigslist and I was able to snatch it with some patience and good negotiating. Negotiation skills are totally underrated, by the way. Truth be told, I did test drive a few airheads, triumphs and jap bikes. But those 70s bikes require a lot more maintenance and some don’t have proper disc brakes! Gotta have my disc brakes – none of this drum braking through the canyons here in LA. Plus, the K100 is known for its reliability and it had enough modern features that made me believe it was a good platform for the cafe… plus someone had done it before, so why not me?

In addition, it was in absolutely perfect condition (never driven, garaged) with all the maintenance done. What else could I ask for? Cafe racer, here we come!!

Just so you know, I’ve finally got all my parts (finally!!) and I’ve started working, making progress on the bike daily. I will start posting pictures of my progress and also detailing the many issues I’ve come across and resolved. Parts lists will also be included.

Tomorrow I will post (w/ pics) about the tear down, selling my parts and the new cafe parts selection. Until then, I leave you with the only picture I took of the “before” K100.



See the image

Last edited by rbarrero on Mon Apr 16, 2012 8:52 pm; edited 1 time in total

Inge K. on Sun Oct 02, 2011 9:15 am

About self cancelling flasher, have read in other forums that this wire can be leaved if you don`t want the function, haven`t tried this myself.

About missing tail light, does the park light in front function? (feed from the same circuit).

About non functioning flasher, remove the relay and measure in the socket.

Terminal 15: switched 12V.

Terminal 30: unswitched 12V.

Terminal 31: ground

Terminal TL: ground when left button is activated.

Terminal TR: ground when right button is activated.

Terminal TA: ground when cancelling button is activated.

Terminal L: output left.

Terminal R: output right.

Terminal 1: self cancelling signal from speedometer.

Terminal C: ground when hazard switch is activated.

Terminal W: output to hazard warning indicator lamp (in the switch).

Inge K.

rbarrero on Sun Oct 02, 2011 2:13 pm

The relay for the turn signals is under the tank? I didn’t remove any relays, so yes, it should still be there.

I read in another forum that all four blinkers need to be connected
before the left or right side will function so I will try that tomorrow.
I’m hoping that is all, or possibly a fuse.

rbarrero on Sun Oct 02, 2011 5:50 pm

Nevermind, it was the fuse! Fixed. Off for the maiden ride!!

rbarrero on Mon Oct 03, 2011 12:43 am

Hi Gents – it’s amazing how fast this little project of mine has come to near completion. It’s also amazing to note that the tail and seat really define the cafe look and make the whole thing come together. It wasn’t until the seat pan was finished and mounted on top of the tail, did it look like the real thing ™. A few tweaks were made to the tail to house the taillight, which looks very good tucked inside with a light slightly protruding out. This was the best way to keep the rear as clean as possible… something a lot of people overlook I think.

In the end it came down to wiring and electrical work to get everything working as needed to do some test drives. The acewell unit works really well and was relatively easy to install. It unfortunately does not take the speed signal from the original harness, so I will have to install the magnetic sensor in the next few days.

After a 50m drive to break the tires and bike in, the k100 still drives and feels as it always did. I wasn’t as hot as it used to feel… maybe since it’s all open, but still warm in the normal sense. Handling with the new bars is great and it feels like I have good movement and control. I’m glad I went with the wider type since it seems to fit the bike better and offer better handling all around.

I could go on and on… but pictures are worth a thousand words, so here you go.

Here it is with the tail but no seat pan:
See the image

The painter matched the color from the tank for the tail and it came out identical… really good work. I had all sorts of custom ideas but this color stands out and looks very classy… perfect for a retro bike of this type.

See the image

Here’s a pic of the circuit described by Inge K. using solid state relays (no moving parts). The unit is probably 1 1/2″ cubed and thanks for the suggestion to use these tiny relays… the others would have been huge!

See the image

See the image

Ordering these solid state relays required reading some specs, selecting the appropriate one (based on a few factors) and finding an online retailer like

Here’s a pic of the seat pan mounted on the tail:
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See the image

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So that’s the tail! Lovely from the back ain’t she?

As you can see, I’ve got the headlight taken apart to fit most of the cabling in there… not a ton of room, but just enough. These are the cables from the harness and acewell unit going into the bucket.

See the image

And after soldering the tail light, blinkers and instrument cluster… I went off with my baby.

See the image

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I haven’t replaced the muffler yet because that’s still a work-in-progress… probably the last thing I’ll do.

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Picture of the acewell:

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Left side:

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Right side:

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I have to also include a picture of the Father and Son team who did the work (that’s me on the right):

See the image

That’s all for today folks! I’ll send an update when I get the magnetic speed sensor installed and the exhaust work done.



Guest on Mon Oct 03, 2011 12:49 am

You need some rearsets? Get rid of those bloody great big ungainly footrests that would support the Sydney Harbour Bridge. I’ve a set of Raask rearsets for the ’83 through ’85 models with the round exhaust mount. They’d go perfectly on there and you’d truly be in the café racer position.

See the image

rbarrero on Mon Oct 03, 2011 12:55 am

Absolutely! I’ve been looking for Raask or Tarozzi rearsets… How much do these go for?

Guest on Mon Oct 03, 2011 1:04 am

I’d sell ’em for a buck and a half, which is about the same as in your money, or close enough these days, plus postage. They weigh about 2 kilos (a bit over four pounds with packaging). Auspost’s website says $66 (beef patty, no tracking, no signature, no extras) up to $101 (tracking, signature, hamburger with the lot) from our East Coast to your West Coast.

I priced some new ones for a project Airhead café I’m whacking together in our workshop and they’re about four hundy Down Undy, new.

charlie99 on Mon Oct 03, 2011 5:02 am

wow nice finish raf …please say hiya to your dad as well hes done a great job at supporting his son …i think i can detect more than one “rev head ” in the family ….giggle

would love to see the new pipe and rearsets fitted up ….

actually the old k sounds real nice with a good pipe …

nice job …congrats

rbarrero on Fri Oct 28, 2011 9:21 pm

@Two Wheels Better – pm sent.

BIG D on Fri Oct 28, 2011 11:26 pm

Great job Raf, that tail peice is so good looking and I love that number plate the cops over here would have a heart attack if they saw that

Fantastic job congrats all round.


scabzzzz on Sat Nov 05, 2011 8:20 pm

I really like this bike. Great story, OP!

Are you going to put a roundel in the tail section? It looks like theres a spot for it. If you addressed that and I missed it, my apologies.

Kingsly on Thu Jan 26, 2012 7:29 pm

Hey Rafael, beautiful job! I found this thread after scouring the internet for info on the K100, as I just managed the score of, well, at very least, this decade: a good shape ’92 K100 RS-ABS for the low low price of… FREE!

Like you I’ve been counting café bikes as I drift off to sleep for the last few years now, and since some of the fairing on the right side was trashed I’ve completely stripped it and intend to follow your lead of building a café brick.

I noticed you’re in Pasadena… I’m in La Crescenta – we’re practically neighbors! Any chance I could peek at your bike and pick your brain??

krambo on Thu Jan 26, 2012 11:18 pm

I’m loving the look of this project – please get rid of that ugly exhaust as soon as you can. It completely spoils the whole cafe racer look Really great work though and I look forward to pics of the finished project

Toto_jp on Fri Jan 27, 2012 2:53 am

My thoughts exactly Krambo I’d be tempted to cut it from the collector and put a 90 mm round stainless pipe on and of course home made baffle 45 mm outlet

rbarrero on Fri Jan 27, 2012 4:14 am

Hi everyone –

RE roundel:
I’ve already purchased a roundel from BMW and will post the pictures the tail with the roundel this weekend.

RE exhaust:
Yeah, the stock exhaust is terrible on the cafe bike… doesn’t suit the bike at all. I’ve been working closely with another friend on this forum and I should have the new exhaust installed soon. Check back for more progress on the exhaust.

I certainly don’t mind if anyone within range (like La Crescenta) want to come take a look and shoot the shit for a little. Send me a PM and we’ll connect.

I haven’t had any time to post some of the latest work or provide an update because things have been extremely busy for me the past few months professionally and personally. I will do my best to upload some new pics this weekend.

Also, if anyone is interested in buying my bike please let me know since it will be going on sale soon.


scheffers on Sun Jan 29, 2012 9:21 am

Cool build! and well written, I was looking for a replacement dash, your experiences on this matter come in handy! thanks a lot!

rbarrero on Mon Jan 30, 2012 7:21 pm

The tail I purchased came with a ~80mm inlay for a BMW roundel so I had to find one that fit. Most of the roundels on the market are either stickers or roundels manufactured for cars, not the motorcycles. So I went to the dealer and asked to see all the roundels and stickers that measured between 70 and 80mm.

The stickers were an initial idea, since that’s what’s used on the tank sides, but it doesn’t look good on the tail, so I needed something with some dimension to it, so it would look good from back and side views. After looking at several roundels, I settled on a Z3 roundel that is usually used for the trunk (or ‘boot’) because it’s the correct size and also it’s a flat roundel…. which is important to note because roundels are made to match the curved body of the newer BMWs, and this curvature would have given way too much height around the edges and would not be affix-able in my mind.

The main issue with the proper roundels (not stickers), is two-fold:
1. they have three .5inch pins
2. they have some empty space underneath (dome like)

So 1) The pins need to be removed cleanly to create a flat surface. Patience and an xacto-knife was required here. And 2) I used an industrial, outdoor adhesive by 3M that comes in strips. I was able to place these strips on the bottom of the roundel and trim where needed…. the strip is almost gel-like and supports up to 4lbs of weight – enough for my roundel sitting on my tail! I added padding in the center of the roundel to make up for the empty space and add some needed surface area for better sticking to the tail. Added lots of pressure for good measure and voila!

That’s it! Here are the pics:

Top of roundel:
See the image

Bottom of roundel:
See the image

Another top view:
See the image

Another bottom view:
See the image

Adhesive on bottom:
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Finished product, BMW roundel on the tail:
See the image

caferacer62 on Mon Jan 30, 2012 7:47 pm

Great looking project RB. If only the fun police here in OZ would allow us to do some of the stuff that yours does.

Shame your putting up for sale after so much effort. Good luck with the sale, don’t think it will be on the market for too long.

zonenfeile on Tue Jan 31, 2012 10:05 am

See the imagefor inspiration

It´s Dietmar´s cafe racer 2011

See the image

rbarrero on Thu Mar 22, 2012 7:34 pm

Hi everyone! Just thought I’d give everyone an update on my bike:

Firstly… The Acewell speed sensor was something that I had procrastinated on for a very long time… but it’s a must-have, especially for prospective buyers. I’ve taken some measurements and developed some sample brackets that I hope to have completed by the end of this week. I will post pictures of the progress this weekend.

Secondly… the exhaust was another point of interest from a lot of you, and myself as well that needed to be re-done to truly finish this masterpiece. I’ve had a friend build me a sweet collector and now I just have to finish the connection to the new muffler. I’ve chosen a shorty reverse cone muffler from Dime City Cycles, and expect it to be prettier and much louder than stock. I’m somewhat concerned about the decibel factor (some people don’t like them loud), so I’m going to do my best to keep the old system around in case the future owner would prefer the stock setup instead.

Like I said, I’ll be posting pictures this weekend and hopefully have it more finished within another week or two.



blakey on Thu Mar 22, 2012 8:55 pm

Hey Olaf, I love the look of the bike in the black and white photo.

Sort-of looks like a hyena to me.

No extra crap. Cut down. Very business like.

kringb on Sun Mar 25, 2012 11:40 am


Thanks for all the detail on your project, especially on setting up the Acewell. I have been working on a similar project and am at the speedometer stage. I have been having trouble getting my neutral light working by using the solid state relay solution that I learned from your story. The gear position indicator function is working but not the neutral light. I started my own thread Here to try to figure it out. The first part of the post deals with getting the fuel gauge to work. Further down I detail my led light problem.

Did you have any trouble getting your neutral LED to light properly?

I am going to try adding a resistor to the circuit. If that doesn’t work and if I don’t get any more leads I will go with mechanical relays.

rbarrero on Sun Mar 25, 2012 5:23 pm

Hi gents – as promised, I’ve got some more pictures of the recent progress regarding the speedo sensor for the acewell unit and the mounting brackets. Don’t have a lot of time cuz I’m flying out in a few hours for work, so I’ll just let the pictures speak for themselves.

See the image

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So that’s it for the speedo sensor and it works well!

Three recent pictures of the bike:

See the image

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New muffler – staging the fitment for mounting.
See the image

Cheers everyone!


rbarrero on Wed Apr 11, 2012 4:08 am

Hi all – back in town and have some good news – the exhaust is done and sounds awesome. I was afraid it would be obnoxiously loud, but it’s not… it’s has a moderately quiet sound at idle and gives a nice rich rumble with some throttle.

This weekend I’ll take some time to take pictures, make a quick video and post it online for y’all.



charlie99 on Wed Apr 11, 2012 6:57 am

cool raf ….eagerly awaiting the update

GeorgiaK on Sun Apr 15, 2012 12:01 pm

Great looking bike. Excellent mod.

rbarrero on Mon Apr 16, 2012 9:26 pm

Hi all – So I’ve finally finished the exhaust on my cafe k100. The main issues here were:

1) figuring out how to get a 4 into 1 pipe collector
2) fitment/mounting
3) muffler install

Collector: I’ve heard that there is a manufacturer that makes a 4 into 1 collector, but I wasn’t able to find one. The solution here was to take a stock system, chop off the part that connects to the headers and then build a thin cone-shaped collector that eventually sizes down into the diameter of the new muffler.

Fitment: I had a requirement for the new exhaust system, which was I should still be able to use the center and kick stand. This was taken into consideration while making the new collector. Not too hard, as long as you have the forethought to remember about the kick stand.

Mounting: Since the old muffler had a mounting piece to link itself to the large rearset, I needed something similar. Unfortunately the new system rides lower and the new muffler doesn’t come with an holding bracket, so I had to make attach a mounting plate to the collector and make a custom bracket that would bolt to the rearset for safety and stability (pictured).

Muffler: I liked a shorty reverse cone muffler I saw one some other cafe racers and Dime City Cycles has one for $50. Compared to the parts, work of the collector, it’s cheap. Here’s the one I bought:

The new setup sounds real nice… I expected it to be extremely loud because the new muffler looks pretty barren inside, it’s short, and weighs about 5-10lbs. Apart from shedding all that weight, @ idle, it sounds a little louder than stock. With some throttle the thing comes to life and sounds robust, throaty and still not overbearing by any stretch. MUCH much better… more appropriate for the look and sensation of a cafe racer. Really breathes new life into the bike.

Without further ado, here are the pictures:

See the image

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Bottom View:
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Side 1 View:
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Side 2 View:
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Rear View:
See the image

There’s really not much left to do with the bike… I am building a small holding bracket for the new LI battery, but other than that, nothing to do except to start riding it!



Kingsly on Tue Apr 24, 2012 4:22 pm

Hey Rafael! I’m glad to see more updates on the bike. I can’t wait to hear a video of that muffler.

Just got all the paperwork in order on mine, a new battery (she LIVES!), and waiting on my very own dcc order.

charlie99 on Tue Apr 24, 2012 4:35 pm

good work raf …i was concerned about the muffler being longer than the rear of the wheel before ….but this looks a whole lot better .


CommanderKewl on Wed Apr 25, 2012 12:20 am

I had bought a few items from Rafael and in our conversations he mentioned that he wanted an exhaust. He had a muffler he wanted to use and after seeing it, i bought the muffler and started working on making the collector ….
I must have used up 20 feet of tubing, several types and configurations.. Some looked radical as i had 4 pipes coming back over the rear sets.. I mitered.. Gritted teeth.. Tossed pieces around.. Bent pieces around my neck.. And then work got into the way..

Spent 7 months in Oklahoma.. Which was only supposed to be 2 weeks.. I got home over thanksgiving morning rested (was doing a 7/12 work schedule at night!) went to a rennaisance festival, got married (black Friday! So i will always remember the day, not the date) honeymoon
Came home worked feverously and then flew back to Tulsa..
Over Christmas, did some more.. Decided to use my only muffler and proceeded to cut that up, for the collector, then the adapters and polished it up..
Look into February before i shipped as i wanted to try a few other polishing techniques, but.. It made me batty as for the life of me i didnt have time to make the mounting plate..
I must have made several more changes to this before i got to this end..

I think Rafael has made quite a ride, kudos to you.

Whew! Just got back into town, so now i need to get my ride up..

From what i heard on my K, it sounds fine. Fine indeed…

charlie99 on Wed Apr 25, 2012 2:24 am

good work commander …interesting mod …but if it works well …hey !!!

rbarrero on Mon Apr 30, 2012 12:40 pm

Hi everyone – here’s a video so you can see and hear the new exhaust in action. I recorded more than necessary (a few minutes) just because it sounds so good… enjoy:

I believe I mentioned CommanderKewl in the past, he’s a really great guy and my new system would not be complete without his work. Many thanks!



Last edited by rbarrero on Tue May 01, 2012 3:13 am; edited 1 time in total (Reason for editing : URL is now a link.)

krambo on Tue May 01, 2012 7:41 pm

Sounds and looks great – a really good project story

charlie99 on Tue May 01, 2012 8:24 pm

sweet !!

Saxon7 on Tue May 01, 2012 9:51 pm

I really like the look of that. Great job! Sound ok?

Saxon7 on Tue May 01, 2012 9:54 pm

Sorry, just saw the link. Sounds good!

alfasteve75 on Sat May 05, 2012 4:44 pm

Could the guest who has the Raask rearsets in Oz contact me. I would love to try them.

rbarrero on Tue May 08, 2012 2:36 am

Hi all – just wanted to post an update… my k100 is in the shop getting new steering bearings as it was feeling notchy and didn’t handle well at low speeds. Once this is done, I’m officially taking her home and I will post some new pictures and videos.

The rearsets would be the next thing to change here… although I’m not sure how that impacts the passenger pegs. A decent pair seems to run about $200, which is a little pricey for something wholly aesthetic/cosmetic.

I still have the original cluster and exhaust can that are up for sale… PM me if interested.



charlie99 on Tue May 08, 2012 3:21 am

alfasteve75 wrote:
Could the guest who has the Raask rearsets in Oz contact me. I would love to try them.

“guest in the house” is his “nic” in here steve …but i think he sold them …

rbarrero on Thu May 17, 2012 1:38 pm

Hi all –

So somewhat recently user ‘kringb’ installed the same Acewell Speedo on his K100 and was able to resolve a nagging issue regarding some of the cluster indicator functions (neutral, hazard, starter, etc)! He used different relays (small, mechanical ones) and also included a diode to implement these features on the acewell. I’ve decided to try it myself since these problems have been plaguing me as well… I’ve just been too lazy to really fix them. Alas, it’s time to do it right and I find myself having more time these days to dedicate a nice evening to soldering.

I should mention that a HUGE thanks is also in order to Inge K., charlie99, and Rick G, who contributed to making this work… you guys really make this forum worthwhile!

Here’s a link to that thread:

I’ve got the new circuit completed, but I’m waiting on getting my baby back from the shop before I can test it out… She’s in for some routine maintenance and I should have it back by the weekend.

For those who are curious, I used four small 12V, 1A relays from radioshack (OUAZ-SS-112D) and a ‘1n4004’ 1amp diode. Here is an updated schematic and some pics:

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Any feedback is appreciated!




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