TECH
Air and fuel system blues – Part 1 and fi nding help on the MOA forum
By Ken Tuvman #133210 I HAD THE BLUES BECAUSE MY K 75 WASN’T RUNNING RIGHT.
My starter won’t start this mornin’ and I’m about to lose my mind. I wanna go and see my little baby but my machine is all outta time. I got water in my gas tank and my battery’s all run down. If I don’t see my little baby I’m gonna leave this lonesome town.
Returning from the MOA rally in Billings, Montana, a bog in the power band devel-
oped at low rpms and she wasn’t idling right. She ran good at higher revs and brought me home to Minnesota. After checking the MOA Flying Brick K bikes Forum and describing her symptoms, I deduced the problem could either be a clogged fuel filter or an air leak. A fuel filter change was overdue, so I installed an OEM Mahle KL145. Wanting to confirm the filter had been clogged, I let it dry, blew into one end, and confirmed it was constricted – problem solved! After a few more rides, I was back to square one. Thinking maybe the fuel injectors
were clogged, I added a half-bottle of Chevron Techron injector cleaner, went for a ride and my bike ran better. The Wisconsin Airheads rally was on my calendar for late September. I own an
airhead, but wanted to ride my K 75 S. She delivered me safely to Wildcat Mountain State Park and the next morning, I joined a small group on a scenic ride. We stopped in Gay Mills, a quaint Wisconsin town to sample apple pie and ice cream during their annual Apple Days festival and the town was buzzing with people taking in the fall colors. As I was heading out, my K bike motor suddenly quit right on Main Street. Fortunately, my MOA friend Curt Henry was there to help. I tried restarting, but she just cranked away. My head flooded with discouraging thoughts of being stuck and having to rent a truck to get home. I began diagnosing the problem. There was gas in the tank. Perhaps it was a bad
Hall sensor, but when we pulled a plug and cranked the motor, we had spark. The next thing we checked was the fuel pump. We pulled the power plug and used a voltmeter to confirm we had power. I read on the MOA forum that gently pushing the starter button primes the fuel pump. There is an audible whirring sound when the starter button is gently pushed, but the noise around me made it impossible to hear it. A thought came to hold the fuel flap down and put my ear to the top of the tank so
I gently pushed the starter button and heard the fuel pump. I pushed it several times and when I cranked her she came to life! I held my breath as we continued our ride back to the campsite. The rally ended Sunday morning and the guys I’d ridden out with were off to the RA
Rally in Arkansas and my solo ride home was uneventful other than the bogging and inconsistent idling when stopped. I now suspected the fuel injectors might be clogged. At a fuel stop in Southeast Minnesota, I added the second half of the fuel injector cleaner. No improvement, but I made it home. Grateful to be home with my bike, I realized there was a greater problem that needed
to be solved. Older machines are great as long as they’re well maintained. Sure, I carry the MOA Anonymous book for insurance, but proper maintenance helps minimize
46 BMW OWNERS NEWS February 2016
the chance of being stuck alone or holding up a riding partner. I posted on the MOA Flying Brick K-Bike
forum again, describing the problems I’d been having. K bike authority Paul Glaves responded and suggested I might be having fuel flow problems due to a clogged fuel tank vent. Chasing the clogged vent theory, I exam-
ined the two hoses that connect to the rear of the fuel tank – one hose catches water/ condensation and carries it outside and the second hose connects to the crankcase via a small brass tube.
Paul later posted that
some dealers and owners disconnect the latter hose and cap it off because venting raw fuel into the crankcase and mixing it with oil in the engine is not kind to the internal parts of the engine. I made a note to check this out. Moving forward, I searched online on the
subject of clogged K 75 fuel injectors and read some posts about
the removal and
replacement procedure. I read about some BMW owners having a good experience with Mr. Injector, a company in Idaho that specializes in testing and reconditioning injectors.
For $17 each, I could ship my
injectors for testing, cleaning and recondi- tioning. I followed instructions on remov- ing the injector clips that attach to the fuel rail and the clips that secure the electrical connectors to the fuel injectors. It is impor- tant to cover the holes where the injectors enter the engine, as you’ll find a large accu- mulation of sand and road debris in this area of the engine. The injector from cylin- der #1 was covered in black soot and the 28-year-old rubber O-rings on all three injectors were hard and brittle. A few days later, I received an email from
Mr. Injector: “Your injectors arrived and have been serviced. They had some minor flow reductions but no detectable leaks when tested on the flow bench. These
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