Early K Fork Noise Fix

By: Michael Pabst
August 1999

Here come the parts needed:

31 42 1 452 011	O-ring	4x
232 057	spring	2x
454 620	valve	2x
621	valve body	2x
07 11 9 932 661	shim	1.6mm
706	shim	1.7mm
…	…	…
709	shim	2.0mm
639	shim	0.1mm
695	shim	0.3mm
934 681	C ring	2x

Alternatively, you could get the sport version kit (incl. stiffer springs and stronger dampening): 31 42 9 058 286 but this runs about 200 German marks, i.e. about 200 $ in the US.

For those w/out the BMW repair / parts manuals: The job is fairly simple / straightforward. Only ‘special’ tool required is a C ring pair of pliers for RR the dampener from the leg.

Installing the above parts requires removing the piston from the dampener rod which requires heating up the piston until the Loctite starts burning. Used a camping cooker – worked fine.

Before removing, mark the piston position to not change the total dampener length. Remove the old valve disc (white plastic) and trash together with the old valve body. Mount 1 of the O-rings onto the new valve, slide it onto the rod with the O-ring downwards, then the small spring (part no …057), then the 2nd O-ring, then the disk with the many holes, then the 2 inch long spring.

Use Loctite red for securing the piston to the rod. Installing the piston / dampener into the leg requires – acc. to BMW special tool number …. but a piece of thin cardboard works as well to compress the piston ring and get it across the valve body edge in the leg.

Finally, you’ll need the right shims – the new valve body is shorter than the 83-85 ones. Use a feeler gauge to determine the shim needed. 1.6 thru 2.0 mm in .1 steps are available. If 2.0 is still too thin, there are .1 and .3 shims available.

Tightening torques (Nm):

• Leg clamp bolt upper: 22+/-2,
• lower: 43+/-3,
• dampener to leg: 20+/-2.

BTW, the late 80s R forks might have the same problem – a friend got that and a similar noise but that’s just speculation from my side so far. Have fun / quiet fork / peace of mind.