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Discussion Starter · #1 ·
Ive had a variety of tips, mostly suggesting me to look at fuel but tank, fuel rail, pump and filter seem to be all good.

It started with an intermittent fault, now it wont start.

The bike would stall dead sometimes when turning corners (randomly).

Now after stalling at the end of a road trip she wont fire up. The fuel was a little low when stalling the last time but thats a side not to the ongoing problem.

It didnt drop cylinders while driving and the spark plugs are nice and whitish.

I've got fuel pressure just not sure how much.
Tried another ECU, cleaned the air flow sensor (wasn't dirty) got a new fuel filter (was kinda blocked), the tank and pump look to be all good, got a new oil filter, tried a car battery (if its the old battery).

Does this sound like a common problem like poor earthing or something?
This is me trying to start it: youtube "bmw k100 trying to start"

Any thoughts would be much appreciated

177 Posts
Memory says to look at Hall Effect Sensor:

"Effectively the Hall Effect Sensor is a crankshaft position sensor. Most modern engines have one in some shape or form. Cars often have it or something similar [abbreviated to a CPS] and sometimes put in horrifically inaccessible places. It gives a signal relative to the rotation of the crankshaft when the engine is running.

The electronics need this signal to know what the engine is doing. If its detected as running you get fuel being pumped, you get spark at the right time. If the signal is faulty or non existent or disrupted in any way these things don't happen [other input signals are also provided elsewhere but ignore these for now]. You get no engine running.

Olde worlde engines had points and ignition timing, typically on a plate on the end of the crankshaft. The K75/K100 HES detects the exact timing of the engine. The plate is adjustable to a small degree but that's for a different discussion.

Age and where they are sited affects them. These Ks came into service 33 years ago and some are still on original units. With any older bike some things might fail and some things WILL fail. The HES is generally regarded as a WILL fail."

Testing the Hall sensors on a K

If that's it one source:

For more help and info I'd go here:

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