Warning: This post is pretty long.  If you treat motorcycle forums like Playboy and just “read” them for the pictures then go to the second post for pictures from my first ride.
 
After taking possession of the Luftmeister turbo’d 86 K75C in early October I’d about “finished” it to the point where I am comfortable riding it.  Having about 115,000 miles on it, many parts of it were, for lack of a better word, ‘tired’ and IMO needed rejuvenation or upgrading.  I spent most of October going through it from stem to stern and finally finished up a few final details around New Years.
 
I’d been waiting for a “nice” day in Seattle when my personal schedule would allow me to take it out in dry, sunny weather but, after getting bored watching football Sunday (the Seahawks won Saturday, what else matters?) I said WTF, geared up and took it for a spin on our ever-wet streets.
 
Here’s the details on it:
 
Though it didn’t come with anal-retentively detailed maintenance documentation, it did come with enough that I was able to piece together an interesting summary of its history.
 
July, 86: Initially purchased from Suffolk County BMW in NY as a black K75 “T” (K75C mod’d by BMW North America to make it more suitable for touring) by a person from San Diego.  Judging from the age/appearance of the license plate that came on it, it appears as though it had always lived/been registered in California.
 
August, 86 – 2,000 miles: Steering recall.
 
October, 86 – 2,200 miles: Instrument cluster replaced. (Don’t know why.)
 
January, 88 – 20K: Modified cams installed. I don’t know any details about how exactly they might have been modified but my guess is that it may have been done to improve low-end torque.
 
March, 88 – 23K: Luftmeister turbo installed.
 
November, 90 – 41K: Engine balanced and valves ground.
 
And then there’s a bunch of other miscellaneous stuff along the way like spline lubes, valve adjustments. steering head bearings replaced, coolant hoses, cables and other typical maintenance stuff.
 
Summary: Although a bit tired in many respects, on the whole it seems as though this bike has been well taken care of and consumed quite a lot of disposable income during its lifetime.
 
 
THE GOOD
 
It’s a running K75. Need I say more? When the shipper delivered it to my house, it was rideable. Probably not ready to go for a big tour but enough so that it started right up and I was able to ride it around the block to the back of my house without risking life and limb.
 
For a bike of this age and miles, it’s in surprisingly good cosmetic shape. From the bent brake lever and broken right mirror it appears as though it recently suffered a driveway drop but the C fairing, windscreen, tank and tail cowl are in good condition and the paint on them pretty darn nice.  Even the roundels are nice. The paint job on the frame is very good so I assume that it has been repainted.
 
All of the turbo components are in good shape: the turbo itself, the headers and the exhaust. I didn’t know much about turbos (still don’t really) but upon inspection I determined that the turbo unit itself has good, unbent compressor and turbine blades and, most importantly, exhibits no radial or axial play so it looks like its bearings are still good.
 
When I pulled the clutch basket off to replace the clutch nut O-ring as preventative maintenance, it looked like the rear main seal had been recently replaced. The clutch was in good shape too so it looks like that had been replaced too.
 
With the exception of the speedometer and odometers, everything electrical, including all of the controls, clock and gear indicator worked fine.
 
C bars.
 
The bottoms of the center stand legs are round and relatively unscraped so that must have been replaced fairly recently.
 
At some point somebody welded about ¾” of additional steel to the foot of the side stand to get rid of the excessive side stand lean typical of K bikes.
 
It has an OEM tail rack in very good condition.
 
It came with a very nice set of city cases that I’d rate as an easy 9 out of 10.
 
Both wheels were in great shape with new Bridgestone Spitfires.
 
Luftmeister “piggyback” shock.
 
 
THE BAD
 
It’s an 86 so it’s got the smoky rings.  Not really an issue to me though as my other K75 Frankenbrick has trained me to turn the bike off and tilt it to the right for a few seconds to reduce/eliminate smoky startups.
 
Although the coolant hoses had been replaced, the rest of the rubber bits on it were shot.  The boots above and below the throttle bodies were all severely cracked and probably leaked like a sieve. My guess is that the most a turbo would do on this bike is push lots of air out of these cracks.
 
The vacuum hose to the fuel pressure regulator was pretty old too.
 
Although they all worked and ran well, the fuel injectors looked like they’d seen 115K miles and never been serviced.
 
The Corbin Dual Sport seat that came on it was in OK shape but is worn through at the front lip and needs a recover.
 
The finish on the gas cap was showing its age.
 
Seat lock hook busted. Not surprising.
 
There’s about a 1” paint blister on one of the battery covers. This is the biggest cosmetic blem the bike has so I’m not complaining.
 
Front master cylinder old and tired.  Combined with that stupid Y system of brake lines that go through the steering head, the front brakes were typically lame.
 
Bent front brake lever.
 
Busted right mirror.
 
Forks a bit faded.
 
 
THE UGLY
 
The Craig’s List ad for this bike mentioned a new fuel pump.  Typically this is a good thing.  However, apparently not wanting to spend $500 for a new OEM fuel pump and damping ring, some mechanically deranged cheap bastard had BUTCHERED the aluminum fuel line in the tank in order to run an external fuel pump that was stuffed under the left side of the tank. The fuel level sender wiring was butchered as well to accommodate this heinous crime. I’ll post more on this atrocity some other day.
 
 
TIME TO GET TO WORK
 
So, that was my starting point.  Below is a quick list of things I’ve rejuvenated and/or upgraded.
 
Even though the clutch assembly was in pretty good condition, I had an even nicer one on hand so I installed that when I had the clutch apart to replace the O-ring. (I replaced all three pieces to ensure good balance.)
 
Replaced the 32/10 drum brake monolever final drive with a K1100LT 32/11 paralever, a freshly rebuilt Works 4V shock and a disc brake with vented rear rotor. With a turbo, this gearing change and the slightly taller 5^th gear of the K1100 transmission I installed, I’d guess that the top speed for this bike is now probably in the neighborhood of 140-150 MPH, maybe more, who knows?  (Since I have no desire to end up in jail or a coffin, I’ll probably never test this theory.)
 
Pulled the clutch arm pivot rod of the K1100 transmission and re-lubed its needle bearings with Mobil 1 synthetic bearing grease.
 
3 spoke wheels with radial tires: Bridgestone BT-023 front and Avon Azaro rear. (Installed new metal valve stems while I was at it.)
 
Rubber mounted K1100 peg plates. (They’re stepped out in the back so that the right one provides clearance for the “hump” in the paralever swing arm.)
 
Early K1100 battery tray. (Less subject to corrosion.)
 
New half-size AGM battery. (This was on the bike when purchased.)
 
Rostra electronic cruise control operated by a K1100LT windscreen switch built into the left combo switch. (Since this cruise control has an output to indicate when it’s engaged, I wired that up to illuminate the ‘extra’ indicator in the instrument cluster next to the low fuel indicator with an amber LED so it’s not too bright at night.)
 
Fully LEDified lower mile instrument cluster with calibrated speedometer.
 
Symtec heated grips operated by an OEM dash switch with ProGrip gel grips.
 
Chromex ceramic coated K1100 bar ends.
 
Wider handlebar mirrors.
 
Dash pad with Powerlet socket for my electrified tank bag.
 
Internal LED backlighting of the two center dash switches to make finding the dash switches at night easier.
 
Altitude plug controlled by dash switch.
 
Backlit LCD fuel gauge. (This also has an oil pressure warning indicator but since the K cluster already has one of those I wired that up so that it turns on when the switch for the altitude plug is engaged.)
 
Replaced the front master cylinder and replaced the Y brake line setup with a new braided stainless line that goes directly from the master cylinder to the right caliper with a metal line over to the left caliper.  Newer, lower mile front calipers. With all that and sintered pads up front I think this is about the best that you can do using the OEM master and calipers. I also installed a front brake lever that has a small set screw in it in order to fine tune braking.
 
Braided stainless rear brake line. (Another advantage of the K1100 peg plates is that the return spring on the rear brake pedal is much better.)
 
Cleaned all of the old grease out of the throttle tube gears and replaced it with silicone lubricant so that the throttle snaps back much better.
 
VGC Corbin Dual Tour leather seat.
 
Replaced gas cap with nicer one. (Rekeyed to work with ignition switch.)
 
Replaced seat lock. (Used old lock core that’s keyed to the ignition switch.)
 
Added nice 22L top case. (Rekeyed to work with ignition switch.)
 
Replaced side case Z racks with less worn ones. (I also spaced the tops of the Z racks out a bit at the top to make it easier to use a key on the inward facing locks of the city cases.)
 
Later ‘S’ forks with Progressive springs and fork boots. Nicer axle.
 
Low mile (7K) starter motor.
 
Low mile (15K) 50 amp alternator. (Also replaced coolant reservoir with a K1100 one since the old reservoir doesn’t leave enough room for the back of the 50A alternator.)
 
Reworked the bastardized fuel system back to where it uses an internal OEM fuel pump mounted where it should be.
 
All new internal and external fuel lines.
 
Newer, lower mile: coils, mass airflow sensor, throttle bodies, TPS.
 
New boots above and below the throttle bodies. New vacuum caps.
 
Got rid of those stupid Oetiker clamps on the TBs and fuel pressure regulator.
 
Freshly reconditioned Bosch Series II four hole fuel injectors.
 
Nicer fuel rail. (Old one had a couple of small rust spots.)
 
New fuel pressure regulator. (Had one on hand. Why not use it while I was swapping in some nicer throttle bodies?)
 
New NGK iridium spark plugs.
 
New Magnecor 8.5mm “competition” spark plug leads.
 
Chromex ceramic coated valve and crank covers. (Replaced cover gaskets and cover bolt grommets with new.)
 
Added exhaust gasket. There was no gasket where the front of the one piece exhaust connects to the turbo.  I’m not sure if it really needs one but figured it couldn’t hurt so I bought some generic exhaust gasket material at the auto parts store and fab’d one.
 
Aux fuse block installed next to the factory one under the left battery cover.
 
Replaced both turbo system air filters with new ones. Covered those with Outerwears water resistant pre-filters.
 
Being a turbo, in order to keep the extra air pressure from blowing out of the plenum into the crank case breather, the bike does not have a crank case breather hose.  It’s blocked off on the plenum and the crank case breather on the engine block has a small breather air filter on it.  I replaced that with a new washable (but non-oiled) breather filter from UniFilter.
 
130/90W Xenon H4 headlight with ceramic H4 socket, 14 AWG wiring and relays.
 
10W fork mounted LED flood lights for conspicuity in traffic.
 
Powder coated 1” square aluminum light bar mounted to the forks under the C fairing with Hella FF50 driving lights that I upgraded to 35W 4300K HID. (Tied into high beam.) At some point it its life this bike had OEM fog/driving lights so I used that OEM relay and some of the already installed wiring for the HIDs.
 
Each side of the light bar has a strip of very bright amber LEDs.  Those are always on but each side flashes off when the turn signal flashes on which makes the front turn signals much more obvious to oncoming traffic.
 
Each of the four side reflectors is backlit by twelve 5050 SMD LEDs. Like the front amber LEDs these are wired up to flash off when the turn signal flashes on so they double as both side running lights and side turn signals.
 
Kisan SignalMinder SM-6 flasher relay with Cree LED turn signal bulbs.
 
LED-friendly BMU I made in order to run LED tail and brake lights.
 
Additional LED tail lighting in side lenses of rear brake light lens.
 
Strobing LED brake lights.
 
Front and rear fender extenders.
 
C fairing Laminar Lip.
 
Replaced wimpy stock disc horns with new Fiamm Freeway Blaster horns. (135 dB - just like the stock horns on RS/RT/LT bikes.)
 
New coolant with Redline Water Wetter, fuel filter, oil filter and Rotella T6 synthetic oil.
 
Synthetic gear oil in transmission and final drive with Guard Dog moly gear oil additive.
 
And I also replaced more or less all of the visible hardware with stainless steel. (Still need to do the oil sump and water pump though.)
 
The first time that I tried to start it since its rejuvenation in late December I discovered that it had a bad fuel injector O-ring on top of the #2 injector as it pissed all sorts of gas all over the cylinder head but after I replaced that it fired right up without any choke or throttle.  Seemed to be running fine so I let it warm up and then sync’d the throttle bodies with my CarbTune. Then got the idle and TPS positioning dialed in.
 

I took lots of pictures along the way that I’ll eventually turn into a project web page.  I’ll update this thread when I put that page up.

The Shakedown Ride:
 
As mentioned in Post 1, yesterday I took it out for a “shakedown” ride for about an hour and a half to run some errands around town and snap a few pics.  Either out of arrogance, laziness or both, I didn’t even bother to bring a toolkit with me. Good thing everything worked fine, eh?
 
Results:  This is a sweet little K. It seems to like the 32/11 paralever and has more than adequate acceleration in the lower RPM ranges .  Since I was just running around town, I didn’t get much of a chance to spin up the turbo but I did take it up over 6K on a freeway on-ramp and it seemed to want to go faster but, since there was a car in front of me, that wasn’t really an option.
 
Though I’ve done something like 18 or so successful Audiovox CCS-100 cruise control successful installs, this was my first attempt at the Rostra electronic CC. I tried it on my short freeway stint and it worked. Sometimes I even impress myself. 
 
When we get a spout of drier weather here, I can’t wait to take it out of the urban environ up to our family’s cabin and see what the turbo really has to offer.  Will it beat a Busa? Meh. Most assuredly not.  But it sure is fun to ride.
 
So, here you go:


 






















The amber LEDs on the light bar are much brighter than they appear in this animated GIF.  My camera exposure came out pretty dark due to the compensating for the brightness of the white fork LEDs.

Wow, a lot of work...but boy, it does look nice!

"But it sure is fun to ride." That's what it's all about!

Great work duck!

Now that's the sort of bike I could own and ride. To someone who knows it is impressive and to those who dont the usual understated quality of the Beemers.
Very nice indeed, a credit to you but having seen pics of your other bikes it is just your usual standard.

Impressive work Duck, hope to hear more about the turbo and the Paralever. Is than 30-40 mm longer wheelbase?
I'm ichin' to know how she handles when you get dry roads? Thanks for documenting.

Brilliant!!!

I know we are all pretty much preaching to the choir here, but seriously, these bikes are made to last, most of us do little mods here and there, but if people really knew what can be done with these sensationally well engineered machines, well... Sorry, I am going to go and have a little ME time with my bike now. And work out how to get a turbo.

Ghost who rides wrote:Impressive work Duck, hope to hear more about the turbo and the Paralever. Is than 30-40 mm longer wheelbase?
I'm ichin' to know how she handles when you get dry roads? Thanks for documenting.

My other K75 (Frankenbrick) has a paralever.  I've ridden that up and down the coast. It's a 31/11 with a complete K1100RS fairing and ABS so it's a bit heavier and slower due to the gearing and weight but it handles just fine.

Duck, your post sounds a lot like my work on the 85 I have, seems like every time I look at something, I say, "well since I am here, might as well replace it"  Soon I will have a new bike!  I hope to get it on the road by March..........

You've done a real good job on those dash switches and controls--I'm taking notes. These projects, however, require advanced planning and take time to come together. So, I'm hoping for next year.

I've already started by acquiring a new/used instrument pod (4K miles) from a '92 K bike that I plan to install at some time in the future. The instrument pod on my '85RT has been upgraded w/LED's, but the clock's going bad and the old two-light low fuel indicators are a bit redundant. I really like what you've done with a digital gas gauge.

The handlebar switches on my bike are all UV faded, though I've re-painted the lettering, it's a kluge at best. So, the next step is to acquire some new switches. I'm glad to see how yours have turned out, so I'll be looking to emulate. I really like the Euro-style headlight switch. I haven't considered cruise control before, but will begin research into it to see how I may like it.

Ya always like to see a top end bike with all the extra's. I've already added fork-mounted Bosch road lights, and have emergency flashers. This year I'm adding heated grips, so that leaves only one switch left on my ignition pod. You're using an altitude switch there, but here in New England we don't have problems with elevation. So, I'm thinking about an engine braking switch that works with the electronics on the carbs instead.

Thanks again and, Enjoy the ride.

-aj

Here's a web page with pictures that's mostly complete. K bike porn!   

http://classickbikes.com/ckb/1.my.k.bikes/13_86.k75t/1.k75.turbo.renup/1.k75.turbo.renup.htm

duck wrote:Here's a web page with pictures that's mostly complete. K bike porn!   

http://classickbikes.com/ckb/my_k_bikes/13_86.k75t/0.k75t.home.htm

It's good to be able to see a project start to (near) finish. By now with those rare sunny January days and rarer warmer temps we've had round the Emerald City you've been able to go for less of a burble and more of a burn.

So, on Tuesday, when it looked like the roads might be dry and above freezing for a few hours, I decided to take the turbo K75 for a ferry ride up to my family’s cabin.  My first chance to actually see what riding a turbo K75 was like. I couldn’t really max it out as the roads I was riding on are often radar’d by the WA State Patrol and sheriff deputies but I did have a chance to test it out while doing quite a few passes. (The guy in front of me on an R1200RT was probably wondering how a measly little K75 was keeping up with him doing 90+ MPH uphill passes. LOL.)
 
If you’ve ever owned/ridden a K75 then you know that it’s like owning two bikes, one below 4,500 RPM and a totally different one above that.  This thing is like three bikes in one.  When I kick down into 4^th gear to pass, I first feel the normal torque curve surge kick in at 4,500 but then when it gets up to 5,500-6,000 or so and the turbo gets spun up, it REALLY gets going and makes it up to 8K in no time.  It’s not a dislocate your shoulders type of turbo pull (my guess is that it’s probably only a 5-7 psi boost) but it’s definitely faster than a stock K75 would go.  (And I changed it to a 32:11 paralever so I’m sure that a stock 32:10 monolever would rip even faster.)
 
Given the lighter weight and the turbo, I’m pretty dang sure that I could easily outride me on my K1100RS.  It had some miles on it when I got it and needed a goodly amount of work to rejuvenate it but for $1,500 I think it’s a helluva K bike. I’ll don’t think I’ll ever sell it.  It’s an awesome little K.
 
Ferry ride:


 
 
The sky was cloudy but I did get some slightly better pictures of it on the way:




 
 
Made it to the cabin:



 
While I was up at the cabin, I rolled it inside where it’s warm and dry and did a few minor things to it:
 





Got rid of the goo on the back of the tank and installed a rubber pad that's supposed to be there:

      

And redid the tail/brake lighting a bit:





Installed a small roundel on the C fairing:


Replaced the flat roundels on the tank with "3D" ones:


LED fuses that illuminate if the fuse burns out:



Fuse labels:


And some other minor stuff...



The ride home on Sunday evening was NASTY. Pouring rain the whole way with winds gusting up to 50 MPH. That made crossing The Hood Canal Bridge interesting.  Then the winds were rocking the ferry pretty well too.  They paged somebody with a blue motorcycle that I think may have fallen over due to the rocking. (My bike was in first gear on the side stand so I wasn’t worried about that.)  Then another drenching half hour to home.

I had a rough-looking K75C for a long Summer season some years ago and thoroughly enjoyed that little machine. I rode it all over Washington state and Oregon. I can imagine a bit of 'blow' behind it from a turbo would be welcome as at times it ran out of urge on long, uphill climbs and at times struggled with a pillion on board. In the end the three cylinder's willing 'rortyness,' but also its smoothness, won me over.

I'll bet the warming thought of being back in the cabin by the woodstove was on your mind. I rode home in that same sideways rain and can say that while it wasn't a subtropical Queensland type of drenching, where it drums down in warm sheets of water for hours on end, it still found ways to get inside my mostly-rainproof riding gear. The gusty wind and water spray from cars and big trucks on the interstate only added to the excitement. For the first time in six years of owning them and using them almost daily, my Gore-tex lined gloves got wet. I was glad for the central heating at home and the dry garage to drip-dry the bike and gear.

OK, it's official. I am in L-O-V-E with this bike.  Until today I really hadn't gotten to play with it through the gears but I went out around town today to run some errands for a few hours and scoot around in traffic and through some turns.  I hadn't realized it before but the modified cams on this bike ROCK.  Imagine a K75 that actually goes somewhere when you twist the throttle at 3,000 RPM.  Oh my!

And, after about an hour or so I was starting to "achieve oneness" with it and understand its character.  After that, Woohoo!  This thing is light years beyond any of the 9 or 10 other K75s I've owned.

I can't wait to take it down the CA coast in a month or two...

Always enjoyed the ferry boats as motorcycles go to the front of the line (and the fare was cheaper).  :arrow: 

Enjoy the ride.

I had the chance to have a look at Duck's new L-O-V-E yesterday, for those who've been following this thread, and can say unequivocally that it's one of the cleanest, most sorted K75s I've seen. Sounds awesome too. Cheers.

Super interesting read..(liked the picture section also).

Looks great mate. I am about to do a Luftmeister turbo install on my ‘84 K100RS. Mine is missing the exhaust from the turbo back, so I will need to fab something up, and I assume (but don’t know) if the kit uses the stock plenum chamber, because there’s no plenum in the box? Any tips or advice re: the installation will be appreciated.

The plenum above the throttle bodies is stock, not custom.

From my emails with a guy who used to work at Luftmeister there were three stages of turbo back then:

Stage 1: Basic

Stage 2: Variable/adjustable intake pressure

Stage 3: Additional fuel injection

I think the Luftmeister consumer kits were Stage 1. My K75 is.

I suspect that the 200 MPH K1 that Matt Capri did was probably Stage 3.

Disclaimer: I am merely a shade-tree mechanic and make no claims that I am an expert on turbo engine management.

Duck,

      Any chance you can strap on a camera and take us all for a spin?