1991 K75S

I picked this bike up for a grand. It has been sitting outside neglected for several years when I bought it.  It needed a lot of TLC but after giving it a full servicing, some new tires, a seat and doing a bunch of mods to it it was a very nice red K75S.

I sold it to a buyer in Sacramento with the understanding that I'd pay to ride it there.  All I needed was for the buyer to buy me a plane ticket home.  I want the long way and wandered down The Cascade mountain range. Great weather and a great ride.

Here's my ride report.

And here's what I di to the bike:

Engine/Mechanical

Reconditioned Fuel Injectors:

Since the bike is almost 20 years old, I had the fuel injectors professionally cleaned, reconditioned and flow matched as preventative maintenance.

Fuel Lines:

The fuel lines were getting a little old so I replaced them with some newer better ones.

Crank Case Breather Hose:

The hose between the crank case and the air box typically gets old and leaks.  I installed a brand new one as preventative maintenance.

Guard Dog Moly Gear Oil Additive:

In order to promote smoother shifting and increase part longevity I added Guard Dog Moly Gear Oil Additive to the transmission and final drive.

I also considered using a Moly additive in the engine oil but since that has the potential to clog the oil filter and these engines will run hundreds of thousands of miles on normal oil I decided against it.

Red Line Water Wetter:

I added Red Line Water Wetter when I flushed and changed the coolant. This provides additional corrosion protection, slightly reduces coolant temperature and improves the heat transfer properties of the coolant.

Suspension/Brakes

Newer, Lower Mileage Showa Forks and Fork Trees:

I upgraded the front forks with some newer lower mileage K75S Showa forks.  Since they have a slightly different diameter than the earlier forks I replaced the fork trees as well.

Progressive Fork Springs:

The forks have been upgraded with progressively wound fork springs to reduce dive on braking.

Fork Boots:

In order to protect the upper fork tubes from pitting or other damage I also added fork boots.

Steering Head Bearings:

Since I was replacing the fork trees it made sense to clean the bearings and give them a fresh lube with Mobil 1 synthetic bearing grease.

Metal Front Brake Lines:

The stock setup for K75 brakes was rather complicated with a line from the master cylinder that attached to the top of the steering head.  Then there was a metal line though the steering head that split off in a Y to normal rubber brake lines to each caliper.

Since this setup has several rubber brake lines in it and the K75 brakes are not super duper brakes in the first place, I decided to simplify and upgrade the brake lines.  This bike has a braided stainless steel front brake line from the master cylinder direct to the right front brake caliper and then a solid metal line from the right caliper to the left caliper.  This minimizes the "mush" in the brakes and makes them stronger and more responsive.

Near New Progressive Rear Shock:

I replaced the crappy stock shock with a Progressive rear shock that is in excellent condition.

Brake Pads:

The front brakes pads are near new and the rear ones are about half way worn so they won't need to be checked for at least another 5,000 miles or so.

Cosmetic

Very Good General Condition:

Seeing as this bike is almost 20 years old and has 42,xxx miles on it, it's got a few minor dings here and there but overall is in very good condition and has never been crashed.  I'd rate it a nine out of ten but I'm selling it so I may be biased.

Perforated Stainless Steel Radiator and Belly Pan Grills:

I made some custom perforated stainless steel radiator and belly pan grills to replace the boring stock ones.

Belly Pan Protected by Line-X Truck Bed Liner:

The lower front lip of the belly pan had some typical nicks and blems in the paint caused by debris kicked up from the front tire. I had the local Line-X shop professionally apply a wide strip of lifetime guaranteed truck bed liner to the lower portion of the belly pan.

Stainless Steel Hardware/Fasteners:

I have replaced all of the visible nuts and bolts on the bike with stainless steel hardware because it makes the bike look a little bit more classy.

Wheels/Tires

3 Spoke Wheels:

Though the 3 spoke wheels became standard equipment in later years, the 1991 K75S came with the older y-spoked style wheels.  These are not only better looking but they are much easier to clean.

New Bridgestone Tires:

Brand new, just mounted, Bridgestone front and rear tires.

Maintenance

OEM Tool Kit:

The bike comes with a complete BMW OEM factory tool kit.

Owners and Shop Manuals:

The bike comes with two computer CDs:

1) This CD contains a PDF of the K75 Owners Manual as well both the Haynes and Clymer shop manuals as well as wiring diagrams and a bunch of other miscellaneous K bike files I've collected over the years.

2) The other CD contains the BMW "ETK" which is the BMW Electronic Parts Catalog (MS Windoze software that was used by BMW car and motorcycle dealers.  It has parts diagrams and part numbers for all BMW cars and motorcycles made from the 70s to 2001.)

Lighting/Electrical

Fork Mounted 70W Orange Auxiliary Lights:

This bike has very orange and very obvious 70W fog lights mounted on the forks.  They are cleanly and simply mounted using stainless steel bolts and spacers on the front fork reflectors.  They are fork mounted to create a triangle with the headlight.  This makes it much easier for drivers of other vehicles to judge your speed and distance.  For motorcycle conspicuity, these are the best lights I've seen and I mount them on all of my bikes.  The radically and noticeably reduce the number of cars that don't see you.

They also do a good job of frilling in under the high beam at night and make great fog lights as well. They are controlled by a 3-way BMW switch in the handlebar dash pad so that you can run them with the high beam at night or the low beam during the day.

Headlight Relays:

The stock headlight wiring is rather wimpy which results in a voltage loss at the headlight and, as a result, less light.  By adding relays and upgrading the headlight wiring there is minimal voltage loss at the headlight.  I've also upgraded the headlight bulb from the factory halogen bulb to a whiter, brighter higher wattage Xenon bulb.  The result is much better lighting and reduced wear and tear on the high/low switch.

Kisan Signal Minder:

In order to run LED turn signals, I replaced the factory flasher relay with a Kisan Signal Minder.

Front LED Running Lights:

I inverted the signal so that the front turn signals are always on to serve as forward/side running lights.  They flash off when they're used as turn signals.

Flashing LED Brake Lighting:

I'm a big believer in having very obvious flashing LED brake lights, not only to keep from getting rear-ended at a stop light but also to get tailgaters to back off. The rear turn signals have red LEDs installed and double as additional brake lights.  I also added some additional LEDs in the sides of the tail light lens that flash when the brakes are applied.  Must be seen in person to be appreciated.

LED Side Reflectors:

To provide additional side visibility at night, I modified the front and rear side reflectors by installing LEDs in them.

Upgraded Alternator:

The original 32 amp alternator would not generate enough power to run a higher wattage headlight bulb and the pair of 70 watt auxiliary lights.  That has been upgraded to a newer 50 amp alternator that has more than enough power.

Upgraded Horn:

The stock horn that came on K75S bikes is a wimpy little scooter horn that is virtually worthless in traffic.  I upgraded that to a much louder Fiamm horn which was used in BMW cars in the 80s and 90s.

Auxiliary Fuse Block:

I knew I'd be adding several electrical upgrades to this bike and I don't like having in-line fuses scattered about the bike so one of the first things I did was add an auxiliary fuse block next to the factory fuse block.

Both the factory fuse block and the auxiliary fuse block also have laminated waterproof labels on them identifying what each fuse is for. (In English, not German.)

Instruments/Controls

Instrument Cluster LEDs:

It's really a pain when one of the instrument cluster bulbs goes out on a K75S.  In order to get the instrument cluster off you have to remove the windscreen, one of the fairing side panels and the headlight.  It's a lot of work just to replace a burned out instrument cluster bulb.

All of the lights in the instrument cluster on this bike have been replaced with specially selected LEDs.  Since LEDs "never" fail there's no need to rip the bike apart for a burned out instrument cluster bulb.  Not only that but the LED backlighting is brighter and crisper at night.

Real Cruise Control:

Yes, REAL cruise control.  As I have with my other K bikes, I've installed real cruise control on this bike.  It works just like the cruise control in a car.  Set the speed and the cruise control takes over. I have this on my other bikes as well and it makes touring a breeze.

Better yet, I implemented it with BMW OEM switchgear in the left combination switch.  This means that there isn't an unsightly aftermarket cruise control switch console to deal with.  It's also quite waterproof and ergonomically very easy to operate with your left thumb.

Heated Grips:

I ride in the winter and determined long ago that heated grips can make a big difference.  I installed new heated grips on this bike.  They're controlled by a 3-way high/low/off switch.

ProGrip Gel Handlebar Grips:

I never liked the stock BMW grips.  As I do on all of my K bikes, I installed ProGrip gel grips on this bike.  They are way more comfortable and work well with the heated grips.

Altitude Switch:

Although many people don't know it, K75s have an "altitude plug" which should be used when riding above an elevation of 4,000 feet.  This tells the fuel injection computer to adjust the mixture to compensate for the thinner air at higher elevations.

The altitude plug could be kept on your key chain and you could pull over when traveling at higher elevations to insert the plug.  This seems kind of ridiculous so I wired the altitude plug to the up position of the emergency flasher switch.  Instead of pulling over to insert/remove the altitude plug when passing through an elevation of 4,000 feet it allows the rider to just hit a switch while riding.  It's much more convenient and there's no risk of misplacing the altitude plug when not in use.

Comfort

Aeroflow Windscreen:

The stock windscreen on a K75S looks cool and all but doesn't do a lot to keep noisy wind and rain off of your helmet.  This bike has an aftermarket Aeroflow which does a much better job when  traveling at speed and/or in the rain.

Seat:

Stock K bike seats are notoriously just plain awful for most riders.  I have both a BMW Comfort seat and an aftermarket Corbin Canyon Dual sport seat for this bike.  You can try both of them out and have whichever one works best for you.

Powerlet Outlet:

The bike also has a Powerlet power outlet above the ignition coils on the left hand side.  This is convenient for running heated jacket/pants/gloves and is also handy to use for hooking up a battery tender when the bike is not in use.

Luggage

Luggage:

Newer style BMW K bike system cases.  These are slightly larger and can hold a full face helmet and are also more waterproof than the earlier system cases.  I also got rid of the cheesy BMW elastic inside them and replaced it with some 3/16" bungee cord which work better and lasts much longer.