50 Amp Alternator Upgrade Kit

50 Amp Alternator Upgrade Kit

This is a common upgrade for K bikes and relatively easy to do. It takes roughly an hour or so and the kits I have include everything you need: a working 50A alternator (over $900 new from BMW!), heavy duty electrical cable, ring terminal and complete, easy to follow instructions. You don't need to be an electrical whiz to do this.

The original K bikes came with a 32 Amp alternator. This is more than adequate for running the bike, heated grips, etcetera but once you start upgrading to a higher wattage headlight (don't do this unless you install headlight relays first), using a heated vest or jacket liner or running auxiliary fog or driving lights the alternator can become overtaxed and the accessories will start draining your battery. In 1993, BMW started upgrading K bikes to a 50 Amp alternator which provides ample extra electrical power for adding electrical accessories.

My 1993 K1100LT came from the factory with a 32 amp alternator. After performing this upgrade I'm now able to run a higher wattage headlight bulb, a pair of 70 watt fog lights, an MP3 CD head unit, a heated jacket liner, heated boot insoles, and heated grips with no problems. If I tried running all of that with my old alternator my battery would be dead before I could ride 100 miles.

The table below shows which bikes came with a 32A alternator and which bikes came with a 50A alternator:

K Bike Model	32 Amp Alternator	50 Amp Alternator
K75	Model year 93 and earlier	Model year 94 and later
K75C	All model years
K75S	Model year 93 and earlier	Model year 94 and later
K75RT	Model year 93 and earlier	Model year 94 and later
K100	All model years
K100RS	All model years
K100RT	All model years
K100LT	All model years
K1	All model years
K100RS(4 Valve)	All model years
K1100LT	Model year 93 and earlier	Model year 94 and later
K1100RS		All model years

It's also very easy to tell if you have a 32 or 50 amp alternator by visual inspection. The alternator is located in front of the radiator coolant reservoir on the right side of the bike. There's a triangular vented black plastic cover over it. By looking at the rear end of the alternator you can tell which one your bike currently has. The rear of the 32 amp alternator is metal. The rear of the 50 amp alternator has a round blakc plastic cover which, if it hasn't worn off, will have "50" on it.

Better yet, the heavy 50 amp alternator can be shipped in a Priority Mail Flat Rate Box which keeps shipping costs down.

If you'd like a 50 amp alternator, you can email me by clicking this link:

mailto:smithduck@gmail.com?subject=K Bike Parts: 50A Alternator Upgrade

NOTE: If you have an early K75 or K100 that has a hose with hose clamps on the side of the coolant reservoir then you will also need to replace the coolant resrvoir as the 50 amp alternator is slightly longer than the 32 amp alternator.