K Bike SPAL Radiator Fan

K75 K100 K1100 Radiator Fan

K bike radiator fans have a high, though not extremely so, failure rate.

If your fan has died, you can still ride your K bike. This is because, under normal circumstances, once you're moving at a decent speed the air blowing by the radiator is sufficient to keep the coolant temperature below ~104˚ C where the fan kicks in. If you're riding in the city where you need to wait at stoplights, then just hit the kill switch when you come to a stop. When the light turns green, start the bike and get riding.

Side Note: If your radiator cap is blowing before the temperature warning light comes on then this is usually an indication that the radiator cap has gone bad and should be replaced. It is BMW part number 17111464720 and costs about $25 from a BMW dealer. (The two rubber O-rings for the radiator cap come with that part so you do not need to buy those separately.)

Fan Repair/Replacement Options:

1) Buy a new replacement fan from a BMW dealer. (Part 17401460427) However, the cost is rather high at $250+.

2) Get a working used fan. All K75s, K100s, K1s and K1100s have the same fan.

3) Buy a Bosch replacement motor. The fan motor is Bosch part 0130007027 and can be had from RockAuto for $54.

3) Buy an aftermarket radiator fan. There are several options but several people have installed a SPAL 6.5" puller fan. Product # 30100402.

Several people have built some very nice custom brackets to mount them on a K bike:

I decided to take a much simpler approach. A couple of 1/8" thick pieces of aluminum bar stock. Since I don't have a 3/4" drill for metal I just cut the rubber bushing at the top in half and placed the mounting bracket between the halves. This approach could be taken with any aftermarket fan.

In order to keep it centered on the radiator, the spacing between the holes on the top piece is 31mm and the spacing between the holes on the bottom piece is 35mm.

I used flat M6 flat screws at points A above.