New Member- K75S-K100

[Putter]

Greetings, Putter here, new to the group. Old to riding motorcycles but new to the K bikes. I have never owned a K bike, but starting to get long in the tooth and its time. Want to learn more about the K75S and K100 bikes. Starting to look for a nice clean K75S and have lots of questions. Want this bike to take me into my twilight years of riding. I am 68 years old now. Kind Regards,  Putter

[The Mighty Gryphon]

Welcome!  My bricks( I've had 5 now) are my "end of life crisis" toys.  Very satisfying to ride and maintain.

[frankenduck]

A newer K75S is better. If you can, buy a 1992 or later.

Improvements over the K75S lifespan:

1989 - Better piston tings that reduce smoky startups.
1989/90 - ABS became available
1990 - Hardened transmission input splines
1992 - Showa forks
1994 - 50 amp alternator (previous was 33 amps)

The ABS is fist generation ABS so it is rather crude and "chunky" (long cycle time) but it does work. Some people like it, some don't. I like it but it wouldn't keep me from buying a nice non-ABS bike.

The 50A alternator isn't really necessary unless you plan to run a lot of electrical extras like aux lights and heated gear. (It's not that hard to upgrade the alternator later)

Earlier K75S models have Y-spoke wheels. I prefer the later 3-spoke wheels because they are easier to keep clean. The alloy of the 3-spoke wheels is a little softer so it can bend if you hit man-eating potholes at speed. (But I still prefer them.)



Ask the seller the last time(mileage) that the clutch splines were lubed.

Check underneath for gear oil leaking from the weep hole in bottom middle front of the transmission. (Right in front of the center stand bracket.)  It's normal for there to be road grime down there but if that hole is leaking gear oil (smells like sulfur) then it means that either the main seal or clutch nut O-ring has gone bad. Replacing either of those is a major project.



If/when you test ride a K75S it is normal for the K75S instrument cluster (and possibly fairing) to bounce around a bit. The main bracket that holds the fairing and cluster to the steering head is made of plastic which can flex a little. The cluster mounting is insulated with rubber which is why it bounces around.

Red K75Ss are fastest.

[Putter]

Thanks Frankenduck! Some great information, will save this. I was wondering what improvements were made in the later years. Good to know about the gear leak, and models when they changed the material for the splines. I always wondered how German engineering would allow the smoking to be acceptable.  Looked at a K75 years ago. It was in the garage on the side stand when I started it up. I did not know about this condition, or thought it was a puff of smoke. When I found the garage door I did not come back. Probably missed a good deal, and it was a fast red one. I do like the red. Talked to a nice fella that was a 1989, claims it will pop out of 2nd gear once in a great while. Nice he disclosed this, but has me worried. Is this common? I am in the states, did not look where you are. Is there a "good" place to shop for the Ks here in the states? Like the idea of buying from folks that care for these bikes. And you helped me make the decision to look for a 1990-1995 model. Think they were still here in 1995. Thanks again, Putter

[frankenduck]

I live in Bumf***, WA. (Rural area.)

K75s were sold in the US thru the 1995 model year.

In general I would buy locally so you can inspect and test ride in person. (Using Craig's List or Facebook Marketplace for example)
That said, I've bought eleven non-local K bikes (five fly-n-ride, one shipped and five that I trailered) without issue but only if I have a good feel for the seller and condition of the bike. On the whole, BMW owners tend to take good care their bikes.

If you're determined to pay way too much then go to the bringatrailer.com auction website.

Rumor has it there were softer metals used in early (pre-90?) K trannies - drum and shifter fork.  But I've had several early Ks and they all work fine so it does happen occasionally but it's not a chronic problem.

K bikes need to be shifted "with authority." Don't stomp on or he-man the shift lever but if you shift too lazily it will drop back in between gears.  Some K riders subscribe to a "pre-load" method of shifting but I've owned lots of Ks over lots of miles and never found the need to do that.

For bikes that have been sitting for a while run your fingers up behind the seam of the low points on each side of the tank. It the paint is bubbling/cracking and comes off on your fingers then that usually means the tank is leaking. Don't buy.

[Putter]

Interesting, It must take a bit to get an Aluminum gas tank to leak? The 1987 with the shifter problem has me thinking. He bought the bike almost new, has 45k on it now. I wonder if he may short shift it or it really has a problem with the tranny. Thats the problem with shopping long distance. Said, at the time it started, the dealer said it was more of a nuisance, interesting.  Ya, that bring a trailer auction place is crazy. Not for me. I may email some big BMW dealers and put some feelers out. Ya never know.  Thanks,  Putter

[frankenduck]

If a bike sits with untreated ethanol-laced gas in the tank for a few years then the ethanol absorbs water from the atmosphere. Since water weighs more than gas it separates and sinks to the bottom. It's not really the water that causes the aluminum welds to corrode and fail but the impurities in the water.

If the gas is non-eth or eth gas treated with something like Sta-bil then this generally does not occur.

[Putter]

Got it, I try to run the good gas, and always store with the good stuff with a stabilizer. On the K75S can I still get new wind screens and many other parts?

[The Mighty Gryphon]

My first brick was a K75RT that I did a Drive-n-Ride from Massachusetts.  It also had shifting issues caused by a loose grub/set screw in the transmission. 

The loose screw resulted in the shift lever not moving the shift drum in the transmission far enough to fully move the shift forks to engage the gears in the transmission.  Some transmissions have this problem, while others do not.  It can be diagnosed by checking the free play in the shifter.  Normally, there is very little free play, and it only takes a relatively small movement to engage the gears.  On my bike, there was a good two inches of slop in the shifter. 

To get to the grub screw you need to pull the transmission, split the cases and remove the screw so you can reinstall it with blue Loctite.  It's a fairly big, but not difficult job.  I did mine in a parking lot 300 miles from home in a little under 7 hours with absolutely no previous K bike experience using the Clymer manual and a handful of simple tools many of which were in the tool kit.  Not only did I address the grub screw, but I also lubed the clutch and drive shaft splines and torqued all the fasteners involved with the rear half of the bike.

45,000 miles later, the shifting is still smooth and positive.  One thing with my bikes is that when shifting between gears, pulling the clutch lever all the way in actually makes gear changes harder.  For the easiest shifting, a light flick on the clutch, pulling it in about a 1/4 inch makes the transmission shift a lot more smoothly. 

[Putter]

Thanks, I may be buying that 87 K75S. Will let you know!! Putter

[Martin]

We can still get aftermarket screens for a 75s in OZ in multiple colours, so I suspect someone in the US does them.  https://www.screensforbikes.com.
Regards Martin.
Clear
Light Tint
Dark Tint
Red Tint
Orange Tint
Yellow Tint
Dark Blue Tint
Light Blue Tint
Solid White Gloss
Solid Black Gloss

[Putter]

Good to know, the 1987 K75S I am looking at needs a new one. I assume the colored ones are non OEM, not a BMW part?  Thanks!

[frankenduck]

BMW sells both clear and tinted:
https://shop.maxbmw.com/fiche/PartsSearch.aspx?&searchtype=undefined&parts=46631456017%0A46631455427%0A%0A

Aeroflow sells a large windscreen that provides better protection:
https://www.aeroflowscreens.com/K75S/K75S.htm

Gustafson sells them but you have to drill your own mounting holes.
https://bikescreen.com/products/bmw-k-75-s

Secdem also has them:
https://www.secdem.fr/en/catalogue-produit.php?reference=BB006HP

Or heed The Rolling Stones:
http://www.motobrick.com/index.php?topic=14858.0