I bought on September a former Swedish police 1992 K75 RT for a project base. It's technically quite good condition, but with 128 kkm's in odo, requires some thoroughgoing service.

A short clip of picking up the bike.



Preparing wheels for powder coating, fork service etc.

Steering head bearing was good. So just cleaning with kerosine and new CRC Super Longterm MoS2 Grease. I also drained the fork oil and flushed the forks with kerosene. I changed the springs to Progressive suspension. First I filled up with 420 ml Motul 7,5 W fork oil. Then adjusted the oil level to -160 mm (fork compressed, without springs), also removed about 10 ml oil. I think about 410 ml will give the -160 mm oil level, if you don't have a tool for measuring oil level. PS springs with the spacers that came with them, gave about 30 mm preload. Oil level and viscosity is easy to change later if I'm not happy, we'll see on May.

My bike has black forks, engine and final drive. I'm still not sure, whether to repaint valve and camshaft covers, since the fairing seals have scraped the paint away a little bit.

My RT had OEM heated grips, working. They were easy to uninstal since also the left heater element was glued to the sleeve which was then fastened by two M4 screws to handlebar. I started replacing the RT handlebar with LSL Flat Track handlebar, which I shortened to 800 mm. 10 mm hole on the middle, underside for heated grip wires and two 3,3 mm holes for fastening the left grip sleeve, then M4 threads. No problems.

The most work was sanding the right end to 22 mm. Almost all bars that are sold as 22 mm bars aren't really 22 mm, but 7/8" which is 22,2 mm. So the throttle grip does not rotate free on that, but the bar end must be sanded to 22 mm. Lots of sweat with sandpaper... I also covered the sanded end with thin layer of paint for protecting against rust.

Most of the service, ignored by previous owners, is done. I'm afraid the drive shaft splines have not been lubed for a long time. They were a bit worn, but hopefully will do still some years. I'm not gonna put so many km's for this bike. Two exhaust valves must be adjusted, but I'm still waiting for the ordered shims. I'll change the brake lines to Probrake Stahflex, but won't do it yet since the front line change requires cooler removal and I've still not got the Samco silicone hose kit yet.

When I get the wheels from powder coating, I'll build the front fender fastening. I also need the wheels for seeing how the bike stands with the new fork springs and Wilbers shock, if I have to adjust the front preload. Just then I'll be able to build the seat fastening to the right position and fit the Leo Vince GP-Style universal muffler to right position.

So far, so good

Those expansive Finnish paddocks looked very nicely raked.

Bit difficult to trump that comment...

​Finishing the service. Two exhaust valves must be adjusted. Also got the brake lines changed to steel braided ones. The hose from front master cylinder to ABS is very tightly fitted under the frame, behind radiator. Removed the radiator first, but just when I got also the ECU loosened I got enough space for changing the hose.

Some progress during christmas holidays.

Keep going! The end product promises to be good.

I knew I recognized that repeating theme being played by the banjo in the background. There's no escaping the collective unconscious.  

Laitch wrote:I knew I recognized that repeating theme being played by the banjo in the background. There's no escaping the collective unconscious.

That's interresting. I got the theme from https://audionautix.com/index.php

I wasn't so happy with the U-shape tube seat mount that I got before christmas. In my mind the seat sat a bit too high from the frame and I found it difficult for fastening hinges and original seat lock. So I let the grinder and drill sing... after few hours I got another solution. It still requires some fine adjusting, but I think it fits better than U-mount.

Sweet, following this, thanks!

​I got the elecrics ready and tested everything that can be tested without starting the engine. Replacing the dashboard was easy with Marulabs BEP 3.0. I also succeded pushing the dash connector trough the frame. The ECU-box must be removed first and it was still very tight between steering lock and frame tubes.

Right side coolant hoses from Samco didn't fit. I got the wrong set of hoses, now waiting for replacement. I first tried to make side-/center stand bracket and use the original ruber pad, but didn't succeeded with the tight and close bends, so I made a new one. Maybe it needs some rubber on it also. Welding 1,5 mm stainless steel exhaust with an inverter and 2,0 mm rutile coated electrodes was surprisingly easy, even the result is not so pretty... just be carefull not to burn trough.

Gas tank and front fender are still at painshop.

My build begins to be ready.

Some notes... I built the bike for my self, for everyday commuting. Not for someone elso or for the show. So, I haven't listened so much for the comments and (good) advice I've got. And I know my built isn't a pure street tracker... My idea was to build a bike it would have been if BMW had built a street tracker in late 80's. So that's why I didn't use any led blinkers or lights or mini bar end mirrors. All the lights and blinkers, as well as the muffler are CE approwed. However, the muffler approval is not for this specific model and it's quite loud, even with the db-killer on. For the first two rides I feel I succeeded. The riding position is nice, the bike handels well. Suspensions is quite sporty, but that's how I like it.

I still have some minor finishing to do, but a test ride was needed for example to know if I must adjust the BEP 3.0 switches before I seal it under the gas tank.



List of modifications:
Cut rear frame, pillion grip from Krad Werk
Cut rear fender
Self made rear fender & blinkers mount
Lucas style backlight
Ermax plate holder
Foundry MC custom made saddle
Self made saddle mounting plate
Gas tank repainted to BMW Indianapolis rot metallic with black stripes by Jani Stenius
Front fender from Krad Werk, painted to glossy black
Self made front fender mount
Self made front brake line brackets
Stainless steel brake lines by ProBrake
Progressive suspension front springs
Wilbers 630 series rear shock
BMW K 75 S mirrors
LSL Flat Track handlebar
Ariete grips for BMW R 1200 GS
Radiator closer to frame, like K75 S and K75 C
Samco silicone coolant hoses from Racebikebitz
Leo Vince GP Style muffler
Self made muffler and side/center stand brackets
Front light 7" and holders from Krad Werk
Acewell CA085 dash
Marulabs BEP 3.0 dasboard adapter
Self made dash mount
Foliatec led warning lights
Powder coated wheels by Laaksojen laatupinta Oy
Engine protectors from BSK Speedworks
Dart Classic flyscreen
Self made radiator protector
CNC gas tank emblems
BMW OEM tankpads
Merit horn
Ariete fork boots from Wunderlich

It's good to see it finished - well done that man!!

Looks good MEK!  Hopefully your commute is long enough each way to really enjoy the ride.

That's an excellent project, you've got a tidy looking bike that'll beat any new bike when it comes to forever reliability, cost and ownership and spares parts, and simplicity and ease of maintenance. Plus, you're the guy who knows it from end to end because you built it.

- and you can alter it or improve it anytime you want!

I'm biased, but I think the K75 is a much better base for a build. The K100 is much bulkier and heavier by comparison, too much so for the extra 'power' (ahem) that it puts out, if not the comparative coarseness over the '75. The '75 just makes a much more usable bike for nipping around on. Just my opinion.

Hope you enjoy it as much as I enjoy mine!

That's it.

"Executive summary"

Now get out and ride it!

False advertising!  You make installing the radiator hose through the crank cover look easy.

chris846 wrote:I'm biased, but I think the K75 is a much better base for a build. The K100 is much bulkier and heavier by comparison, too much so for the extra 'power' (ahem) that it puts out, if not the comparative coarseness over the '75. The '75 just makes a much more usable bike for nipping around on. Just my opinion.

Agree wholeheartedly with this.

(But then again I'm a slut for K75s.)

Great result well done. I wish I’d seen that trick with the rad hose before I did mine .

tinyspuds wrote:Great result well done. I wish I’d seen that trick with the rad hose before I did mine .

Silicone spray and zip tie or wire around the hose to shrink it, so the hose goes easy through the crank shaft cover.

top stuff ...thanks for posting this

charlie99 wrote:
top stuff ...thanks for posting this

+1

Nice one!!!!

A very beautiful place to ride and I loved hearing the 'burble' of the K engine.  They really do sound unique.  Thanks for sharing that!

Water pump seal was leaking coolant, so the seals and ruined shaft must be replaced.



Also changed fork bushings.



My K75 also got a facelift with BMW R Nine T Urban GS fairing. Welding the headlight/meter/fairing mount was lots of measuring, bending, welding and grinding. I also replaced the OEM fork brace by self made version. Fork boots didn't really fit so good with the OEM brace. Both were powder coated. Since the style not really is pure street tracker, let it now be K75 ST, by the R80 ST, the sister model of R80 G/S.

Also changed the muffler to the model specific Hattech.

I test started the bike on February after the water pump replacement and all worked fine. Three weeks ago I got my brand new GS and swapped the K75 to car shelter and the new R1250 GS into the garage for adding some equipment. I renewed the battery to K75 a year ago and it has been on CTEK charger the whole winter, so I was really surprised, when the starter could not crank the engine. I then took a jump start from my wifes car and it started fine.

When testing more, sometimes the starter could crank the engine, but mostly not. So I disassembled it and found the other brush quite worn and the starter full of coal dirt. I ordered a full repair kit from tills.de. Let's see if cleaning the starter and replacing brushes and bearings helps. If not, my next suspect is the Hall effect sensor. It may be repairable as well, at least the wires.

-mek-: do NOT polish the copper segments on the armature. The carbon marks you can see on there are filling microscopic pits in the copper. It gives the brushes a smoother ride and a greater contact area. By all means, gently scrape out the dirt between the copper segments.

Dai wrote:-mek-: do NOT polish the copper segments on the armature. The carbon marks you can see on there are filling microscopic pits in the copper. It gives the brushes a smoother ride and a greater contact area. By all means, gently scrape out the dirt between the copper segments.

Thank's for the tip.

I overhauled the starter and cleaned all ground and power connectors, won't start. Yesterday I got help from my wife and was able to check the voltage also when starting. Battery had 12,6 V, but when starting, it dropped under 7 V. Somehow my Ctek XS 3600 charger seems to destroy batteries during winter (battery was one year old Exide AGM battery, 19 Ah). It sure isn't any plug in and forget -charger. I got new battery yesterday evening, just before the local part shop's closing time. With new battery it works brilliant again.

Thinking positive, the starter should have been overhauled anyway quite soon and specially the ground connectors are quite common reasons for starting problems also, so it's good all are checked and clean now.

Bad thing is that we still got 5 cm new snow last night, next few days it will still be just around zero, so not yet riding.

Photos of K75 "ST" after modifications I made last winter.

Saddle - BMW R80 G/S, ST, modified
Screen - BMW R nine t mask
Muffler - Hattech

Great job on the K75 - I'm another big fan of a slimmed down version of this model.

You will find the R80G/S seat much better. I have both the dual seat and the single seat for my R80G/S and I find the single seat more comfortable than the dual version. In fact I used that single seat for a short time on my K75 as I was still working my way through the style that I wanted.



which ended up looking like this


Enjoy your summer!

Short video of last winter modifications.
 

I set the end to this project and sold my K75, time will tell what happens next. Thanks for all for the support and advice.