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91 K75S Barn Find

M

motiv8ed

R69S,R75/5,R90/6,K75C&S
Recently found a 91 K75S w/13k miles. It’s been idle since 2008 so I’ll be chipping away at the various well documented gotta do’s. Previous owner had their local BMW shop attempt to bring it back to life with a new fuel pump & kit but a fuel leak and the rapidly escalating invoice provoked the sale. Upon receiving the bike, I put a gallon of fuel in, installed a new Westco Battery, a new Starter Relay, and gave it a whirl. To my surprise, it started immediately and purred like a K75 should. After 10 min or so I killed it as fuel was leaking out both sides of the tank. Interestingly, the starter continued to churn, so I disconnected the batt. I whacked the new starter relay and started it again and upon shutting it down, same thing…..kept chugging. So I’ll be trying to find what’s causing the relay contacts to weld, given the batt is new and fully charged and the relay is new as well. Any thoughts/ideas from the Brick Brain Trust would be appreciated.
Upon removal of the tank no obvious holes were found. The fuel appeared to be coming from the fuel sender mounting point, so now I’m in the process of replacing the corroded fuel sender and o’ring and will complete a leak check next.
 

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Welcome to the Forum!

Great find!

Make SURE new battery is fully charged. Check voltage across the battery terminals while cranking.

Check condition of ground wire from battery to bolt on side of transmission just above shift lever.

Check the voltage to the large wire that leads to the relay from the battery. Should be battery voltage.

Then check voltage to starter while cranking. Should not be lower than 10V.

Check the voltage to each of the small wires going to the relay while cranking. Should not be lower than 10V. This could be a sign very dirty ignition or starter button contacts.

Check voltage at fuse#1 key on. Should be within .5v of battery voltage.


The fuel leak is probably the O-ring (cheap) 62 16 1 459 608 GASKET RING $8.42, unless you can see something wrong with the sender (expensive) $306.


Get back to us with results.



:dance:dance:dance
 
Last edited:
Replaced very rusty fuel level sender & O’ring as well as the battery ground strap, and the starter run on issue is gone. The fuel leak is also gone. I cleaned the gas tank and replaced the fuel filter as well while I was in there. I’ve ridden the bike around the neighborhood and it seems to be running fantastic with great clutch feel, shifting, stopping etc. ABS light is blinking, so I’ll take a brief dive into it, but not overly concerned.
 
Barn Find K75S

98lee said:
Welcome to the Forum!

Great find!

Make SURE new battery is fully charged. Check voltage across the battery terminals while cranking.

Check condition of ground wire from battery to bolt on side of transmission just above shift lever.

Check the voltage to the large wire that leads to the relay from the battery. Should be battery voltage.

Then check voltage to starter while cranking. Should not be lower than 10V.

Check the voltage to each of the small wires going to the relay while cranking. Should not be lower than 10V. This could be a sign very dirty ignition or starter button contacts.

Check voltage at fuse#1 key on. Should be within .5v of battery voltage.


The fuel leak is probably the O-ring (cheap) 62 16 1 459 608 GASKET RING $8.42, unless you can see something wrong with the sender (expensive) $306.


Get back to us with results.

Thank you for the help, Lee! Much appreciated! Running sweet now!



:dance:dance:dance
Click to expand...

Thank you for the help, Lee! Much appreciated! Running sweet now!
 
When your ready to address the ABS, I would ask that you start another separate thread on that one. This will help others when they are searching for a similar problem.

Please include the year and model (K75S) in the title of the thread.

There is a good chance that all it needs is to be reset. They are pretty easy to troubleshoot.




:dance:dance:dance
 
Congratulations! I would love to find such a project since I have never owned or riden any K series cycles and the K75 is my favorite among them.

Best of luck with the rest of the revival project.

Be well, ride safely.

RK
 
K Bikes

miseenscene said:
Congratulations! I would love to find such a project since I have never owned or riden any K series cycles and the K75 is my favorite among them.

Best of luck with the rest of the revival project.

Be well, ride safely.

RK
Click to expand...
Thanks for chiming in. I’ve been a long time airhead guy but stumbled on and purchased a 1 owner 87 K75C w/12k miles last summer and have enjoyed it immensely….so much so that I started to search for an S and found the purple one in Wisconsin and had it shipped here. Sadly, I purchased both of these K75’s from the widow’s of the original owners, so it adds something special to the experience. I feel obligated to bring them back to life and enjoy them like the original owners did.

I’m only 7 months into my K75 experience, but I’m smitten. While I try to ride all of my bikes weekly throughout the riding season, the K’s are my more oft chosen steed of late.
 

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motiv8ed said:
Thanks for chiming in. I’ve been a long time airhead guy but stumbled on and purchased a 1 owner 87 K75C w/12k miles last summer and have enjoyed it immensely….so much so that I started to search for an S and found the purple one in Wisconsin and had it shipped here. Sadly, I purchased both of these K75’s from the widow’s of the original owners, so it adds something special to the experience. I feel obligated to bring them back to life and enjoy them like the original owners did.

I’m only 7 months into my K75 experience, but I’m smitten. While I try to ride all of my bikes weekly throughout the riding season, the K’s are my more oft chosen steed of late.
Click to expand...

"While I try to ride all of my bikes weekly throughout the riding season, the K’s are my more oft chosen steed of late." Anyone who has ever owned a classic K-bike, and especially a K75, completely understands that statement. :groovy
 
K75

GREGFEELER said:
"While I try to ride all of my bikes weekly throughout the riding season, the K’s are my more oft chosen steed of late." Anyone who has ever owned a classic K-bike, and especially a K75, completely understands that statement. :groovy
Click to expand...

Hi Greg, seeing your location, you must recognize my location in the pic. Good to see there’s at least one other air/brick head in the area.
 
GREGFEELER said:
"While I try to ride all of my bikes weekly throughout the riding season, the K’s are my more oft chosen steed of late." Anyone who has ever owned a classic K-bike, and especially a K75, completely understands that statement. :groovy
Click to expand...

100%! The K75s gets the nod most times when I head out to the garage. Not quite sure what it is but it is my go to for errands, most running around, and a few journeys this past year.
 
veefore said:
100%! The K75s gets the nod most times when I head out to the garage. Not quite sure what it is but it is my go to for errands, most running around, and a few journeys this past year.
Click to expand...

Maybe it's the way a K-bike starts so quickly that is seems you haven't even fully depressed the starter button. For me, starting an airhead is like waking something that was sleeping, but starting a K-bike seems like it was already ready to go and just waiting on you. :brow.
 
GREGFEELER said:
Maybe it's the way a K-bike starts so quickly that is seems you haven't even fully depressed the starter button. For me, starting an airhead is like waking something that was sleeping, but starting a K-bike seems like it was already ready to go and just waiting on you. :brow.
Click to expand...
same with an oilhead, just doesn't start as easily as a K75.
 
GREGFEELER said:
Maybe it's the way a K-bike starts so quickly that is seems you haven't even fully depressed the starter button. For me, starting an airhead is like waking something that was sleeping, but starting a K-bike seems like it was already ready to go and just waiting on you. :brow.
Click to expand...

:thumb:thumb
 
1987 K75S frame off restoration

Love these stories about K75 !

I've been told these bike we not quite accepetd by the BMW afficionados back when they were new. A resl BMW was air cooled, vibrated, has a torque induced effect with gas on, etc...

I've been riding bikes since I was 18 ( now 60' still riding...). Gone through most japanese, with one exception, a F650 GS bought to do the Trans Labrador (gravel) highway in savage camping. A great ride by the way.

Lasr september I bought a naked K75 black with the little silver stripes and the low seat. A set up make it looking like a vintage bike. Really not expensive, rideable, but with needs. Brought it home on its power from Quebec, a fantastic 850 km ride.

Then, next wednesday, scolling through Facebook Marketplace, surprise, a nice red K75S appeared for the whooping amount of 1199 $ CDN. Called the guy and a deal was struct at $ 900. Next friday was the pick up with a closed trailer this time as the engine was supposed shot. But hey, the bike had 2 new tires, and a very clean Corbin seat. Figure this would be the "parts bike" to restore the nake 1989 K75.

I did try to start the S, and so much smoke was coming of the tail pipe, and a horrendus clacking sound was comming from the engine... Changed the oil and got 6 liters out of that poor S. As for the sound, after reading about it, found it was the rubber grommets of the alternator. so the naked bike gave its alternator to the S and... Tadaaaa ! No more sound, and with the corect amount of oil in the sump, no more smoke out of the exhaust !!!

I've sorted little things, like taking a squirell nest out of the airbox, major cleaning, plugs, major check up, and voila. Yes it was leaking oil by every seals and gasket, and that weeping hole in front of the engine, but no oil in the coolant and no coolant in the oil though.

Been riding the S nearly 1000 miles before winter struck, and it was determined that it was the keeper ! Still the S begged for more than a clean, so...

Actually undergoing a major frameoff restoration. I know I will be under when finished, but I don't care I so much love the feeling and everything about this bike, that it will likely be my last ! They'll bury me with it ! It is suprising that these bike goes for so little money, even the nice ones.

This is the K75 story up to date for me !

Great Bike, I mean really great,

Have a nice day everybody

Ignace

1989 Naked K75
1987 K75S
 

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fuego said:
Love these stories about K75 !

I've been told these bike we not quite accepetd by the BMW afficionados back when they were new. A resl BMW was air cooled, vibrated, has a torque induced effect with gas on, etc...

I've been riding bikes since I was 18 ( now 60' still riding...). Gone through most japanese, with one exception, a F650 GS bought to do the Trans Labrador (gravel) highway in savage camping. A great ride by the way.

Lasr september I bought a naked K75 black with the little silver stripes and the low seat. A set up make it looking like a vintage bike. Really not expensive, rideable, but with needs. Brought it home on its power from Quebec, a fantastic 850 km ride.

Then, next wednesday, scolling through Facebook Marketplace, surprise, a nice red K75S appeared for the whooping amount of 1199 $ CDN. Called the guy and a deal was struct at $ 900. Next friday was the pick up with a closed trailer this time as the engine was supposed shot. But hey, the bike had 2 new tires, and a very clean Corbin seat. Figure this would be the "parts bike" to restore the nake 1989 K75.

I did try to start the S, and so much smoke was coming of the tail pipe, and a horrendus clacking sound was comming from the engine... Changed the oil and got 6 liters out of that poor S. As for the sound, after reading about it, found it was the rubber grommets of the alternator. so the naked bike gave its alternator to the S and... Tadaaaa ! No more sound, and with the corect amount of oil in the sump, no more smoke out of the exhaust !!!

I've sorted little things, like taking a squirell nest out of the airbox, major cleaning, plugs, major check up, and voila. Yes it was leaking oil by every seals and gasket, and that weeping hole in front of the engine, but no oil in the coolant and no coolant in the oil though.

Been riding the S nearly 1000 miles before winter struck, and it was determined that it was the keeper ! Still the S begged for more than a clean, so...

Actually undergoing a major frameoff restoration. I know I will be under when finished, but I don't care I so much love the feeling and everything about this bike, that it will likely be my last ! They'll bury me with it ! It is suprising that these bike goes for so little money, even the nice ones.

This is the K75 story up to date for me !

Great Bike, I mean really great,

Have a nice day everybody

Ignace

1989 Naked K75
1987 K75S
Click to expand...


Excellent story, and very typical of someone getting to know these wonderful bikes. Good luck with your restoration. Please post pictures along the way and especially when done!
 
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