A flaky HES will typically fail when it heats up. A K bike will start and run just fine when cold but will then suddenly quit once it heats up. After you wait a few minutes the HES cools down so that the K will start and run again.

The HES is located under a rectangular cover on the front right of the motor:

The HES cover is held on to the motor by five M6x20 bolts with a cork gasket:

Diagnosis - Cold:

Carry a bottle of cool/cold water with you when riding. When the bike quits and won't start right back up then try pouring water over the HES cover. If the HES is failing then that should cool the HES to get the bike running until the HES heats up again.

Diagnosis - Heat:

At home, take the HES cover off. Be careful with the gasket when doing this. It's only a $4 part if you do mess it up though. BMW part 11141460307.

With the engine cold or cooled down, start the bike and then see if you can induce a HES failure using a heat gun or hair dryer.

Replacement Part:

All 4 cylinder Ks (K100, K1, K1100) use the same HES, BMW part 12111459033. The two sensors on it are 180 degrees opposed.

 

Having 3 cylinders, K75s use a different HES with the sensors 120 degrees apart. BMW part number 12111459049.

Installation:

When replacing a HES, in order to keep the engine timing correct, all you need to do is rotate the HES to align the notch on the HES with the arced notch on the engine block before tightening the bolts that hold it on.

 

© 2013 Drake Smith - Please do not use or reproduce this elsewhere.  Feel free to link to it though.