Hello, my name is William but I chose the name puffalot apparently ‍�. So I have been a fan of bmw bikes for a few years now. I had a rental house in Charleston SC where I was working and the landlord had a deck boat and a bmw motorcycle. For electrical favors I had full use of both. Last month I came on a deal I think.....a 1987 k75s in pretty good condition for $1,000 OBO. The ad said that it ran last year ‍�. I watched some YouTube videos 🤪 and figured what the hay I can probably just put some oil in the sparkinator 1000s and vroom. I went to offer the guy $750 and see what happened. I saw the bike and instantly saw a spot in my garage for it. He asked if I wanted to hear it run? Then cranked it. I told him I thought I was buying a non running bike so I was prepared to offer $750, he said sold and gave me the title and delivered the bike for me as I had went in my car on my way home from work. I actually put 4-500 miles on it in the last few weeks. Experiencing several different kinds of run ability issues. First seemed to be near WOT there was a dead spot, kind of like it stopped taking gas, then it would literally be fine for a while. Then it started idling high, around 2k so I had been doing some reading here and there. Yesterday after work I noticed one of the spark plug wires coming off of the front fire maker was pretty loose. I put it back on tightly and took her for a spin around the block and through my little town square. She ran like a scalded pig and would rise up from second to third! I got close to home and she started acting funny again, rolling idle then as I was coasting down my driveway it was 2k idle again. I parked her in preperation of driving her to work this morning, I haven't had her let me down since I got her running rough or not. I went back out later yesterday evening and installed the license plate ‍� yeah I was waiting on a nice bmw frame to make it cooler it still hasn't been found/ordered but Raleigh Nc isn't to be messed with without a tag. I also wanted to check the big air plastic piece that goes into the side of the air box. I took that off and noticed several of those small acorns in there🤨. Got out what I could reach and put the plastic pipe back in. It didn't seem to be a source of un metered air. I cranked her up and goosed her once ir twice to hear that triple whine. She settled down to idle and I reached over the seat/tank area from right side to left and as soon as I touched the seat area with my chest it cut off. and hasn't cranked back yet. The battery is down some so I have her on a trickle charger. Does anyone have a picture of the 4 pin connector under the tank? Or is it obvious when you see it? Wirenut by trade so I'm pretty good at spotting bad joints

Puffalot wrote:Does anyone have a picture of the 4 pin connector under the tank? 

Welcome, William. That's a heck of an introduction but you haven't told us whether you like kitties, take sunset walks along the beach, or have a significant TikTok presence. Post future troubles in the troubleshooting section. I'm easily disoriented.

Regardless, here's a photo of the connector beneath the fuel tank/seat, foot-brake side.


Also, go to the shifter side of the moto. Under the seat is the fuel injection control unit. It has a long and large black plug with a large cable connected to its right end. If you can pull that end of the plug outward and swing it left, the plug isn't latched and was only making intermittent contact to keep the moto running. Push it in until it latches and you can't pull it outward. Green arrow indicates the L Jetronic control unit; red arrow indicates the end of the plug.


There are so many other conditions that could contribute to this in a decrepit, 34-year old moto, it's breathtaking, but your acute awareness of cause and effect might be right on the money.

Thanks Laitch! My plug apparently has been tampered with because it is on the rear brake side I think this bike was owned by some fairly intelligent people in its past. I actually got a notebook with previous owners and their address....too much of a coward to contact them I guess. And I do apologize for mag dumping all of that right after introducing myself here. I'll do better. I will regroup and post a few questions I have on the current situation. I'm already leaning towards a couple different things that could cause my issue, I have 2 other bikes a 1985 goldwing limited edition gl1200 and a 2001 Suzuki intruder 1500LC. I wouldn't take anything for this bmw though, its character speaks to me in a way no other motorcycle has. Anywho thanks for your reply and providing these pictures! I was thinking it might have been a different connector, that one hangs down beside the seat really on my bike.

So I got home this afternoon and thought to myself I can go through all the hoopla to check for fuel, spark and what not....orrrrr I could just take the gas tank cap off and have a look inside. I immediately found my problem lovely! Just a aftermarket fuel filter that is a little too short and slid out of the hose clamp! Keep bricking my guy the german engineering is the best!

Is that a 1/4" hose barb on that filter???  Should be 8mm or 5/16".  

If it is 1/4" that may be why it came apart.  Also, those worm gear hose clamps are not the right way to clamp high pressure fuel line. I'm wondering now if the fuel line is the right stuff for immersion in a fuel tank.

Thanks, yes none of this looks right I figured the way she had been running that it wasn't anything big that caused her no start situation. I consider this a win so far.

Get some new lines, filter and original hoseclamps, the buggin' bitch will run forever with that

Hi Puffalot, Let me know if you ever find yourself down in Charleston again since I live in Mount Pleasant and have firsthand knowledge of the K75. I have a 1990 K75S that I turned into a 'Speedway Racer' style of cafe bike (sorry purists) learning about the various systems as I went. Online videos and the CL***R BMW K75 and K100 repair manual were a huge asset for me so these resources may help you as well. -- Stay Safe

mlogan32 wrote: 
I have a 1990 K75S that I turned into a 'Speedway Racer' style of cafe bike (sorry purists) . . .

If you're really sorry, mlogan, and want to make amends, I'll accept a gift certificate from Morse Farm of East Montpelier for a large maple creemee, then I'll forgive you.

A large maple creemee does sound really good... I'll see you in 17 hours and 5 minutes.

mlogan32 wrote:A large maple creemee does sound really good... I'll see you in 17 hours and 5 minutes.

Don't trouble yourself. It's July 4 weekend and you don't want to get caught in the Cross Bronx snarl. Just have Morse email me the certificate. You'll be forgiven regardless of your whereabouts. Relax among the azaleas and gardenias. 

@mlogan32 I appreciate it, from the paperwork that came with this bike it was actually owned in SC and work was done at Murrels Inlet. I thoroughly enjoyed my time down there and I rode through Mt. Pleasant everyday to get to Daniel Island. I'm finding that these bikes aren't very difficult to work on but the directions are kind of vague on how to do it. Adjusting the clutch is on the agenda for this morning. Wish me luck