K1 eng. and tac. problem?

[utiuti]

I started my K1 (91) today and found it running poorly. I thought it was only cold and started to drive off. After 3 blocks i noticed that the tachometer was not running. I decided to turn back and the bike stalled out. Got it started after a several tries.
Driving back i the bike seemed to only run on two cylinders, but all of the sudden the tachometer started to run and the bike fired up on all 4. That was only short lived and the tac. quit working and the engine went back to running poorly. The battery was dead by the time i got home.
What could be the problem?

[PGlaves]

I started my K1 (91) today and found it running poorly. I thought it was only cold and started to drive off. After 3 blocks i noticed that the tachometer was not running. I decided to turn back and the bike stalled out. Got it started after a several tries.
Driving back i the bike seemed to only run on two cylinders, but all of the sudden the tachometer started to run and the bike fired up on all 4. That was only short lived and the tac. quit working and the engine went back to running poorly. The battery was dead by the time i got home.
What could be the problem?

Somebody can be more specific - but it is either a bad coil or a bad wire/connection to a coil. One of the two coils - that fires two of the cylinders - and the same coil the tachometer pickup is connected to. It is very likely a bad connection - or if the primary in the coil that provides the tach signal goes intermittently open we have exactly your symptoms.

[Teslaesque]

This sounds very much like a coil problem to me. The tach wire is connected to the coil closest to the front of the bike. If that coil were not working, or working intermittently, you'd get 2 cylinders not working combined with a dead tach. you may want to check my posts on a recent, somewhat similar problem here:

http://www.bmwmoa.org/forum/showthread.php?t=29360.

also, a very good wiring diagram can be found on this page:

http://www.bmwons.ca/k100/k100.htm

good luck!