When bleeding the front brakes, turn the handlebars all the way to the left. That puts the master cylinder at an upward angle. If you leave it straight ahead, the master is at a downward angle and the is a high point at the front of the master where air gets trapped.
You may be best served by replacing the filter and fuel lines in the tank and check the mesh cover on the bottom intake of the fuel pump. I'd also check the rubber boots on the throttle bodies and the crankcase breather hose for cracks. Have you considered pulling the injectors and sending them out to someone like Mr. Injector for cleaning / rehab?
I would pull the tank to clean and grease all the connections and grounding points.
If you have a fuel pressure issue, the FPR substitution of recommended brands and part numbers are below.
Either a Napa/Echlin 21709A
or a Standard PR134 would work fine in any early K (brick).
With further curiosity and diligent searching I also learned that the Standard PR134 is OEM equipment on many different cars ranging from late 1970s Porsche
911s to VW Vanagon and Super Beetles as well as JEEP, AMC, Chrysler, Audi and Jaguar models in the late 1970s to mid 1980s.
They're both valid substitutes that cost less than buying from BMW
Just noticed this thread and started thinking about either replacing or rebuilding my rear master cylinder ('94 K75S with ABS). It's time I flushed and bled the brake lines so I might as well take care of all the details when I get to it.
Quick question: How difficult/easy is it to rebuild the rear MC?
I've never done one before but as it seems to only weep a bit of fluid over time I might be OK with just a rebuild rateher than replacing the whole shebang.
Judging by one of the above posts I suppose I need a circlip removal tool to do so; sounds like something that I could find at Harbor Freight---any special size?