We will assume that you are having problems getting the suspension of the forks to work properly, otherwise you probably wouldn’t even be reading this. They are sticking, either not compressing smoothly, or sometimes not returning all the way after compression or after rebounding.
We will start by preparing the forks for checking and adjustment:
*Use a rope or ratchet strap to secure the center stand to the exhaust crossover to assure that the stand will not fold up.
*With the assistance of a helper, lean the bike over and have the helper place the 2×12 under the upraised leg of the center stand. Then tip the bike up towards vertical again and pivot the board under the other leg of the centerstand. This will get the front of the bike high enough to easily remove the legs. You can see that the board is in place in this photo
*Remove the gas tank and get it out of the way.
*Loosen (just barely break loose) but do not remove the hex nuts at the bottom of the fork legs (the nuts that you normally remove to drain the forks) before removing the axle, otherwise you will need to replace the axle to hold the legs in place.
*Remove the fork oil filler bolts at the top of the upper spring retainers
*Loosen the upper spring retainers (the big nuts up on the upper fork bracket) before disassembling the lower front end. It’s a bit easier at this time.
*Remove the front wheel, brake components, speedo cable (if so equipped), and all other related items as necessary. Do not let the brake calipers on disk brake equipped models hang by their hoses. Use some sort of wire hanger or light rope to tie them up.
*Remove the front fender and fork brace and after market fork brace if so equipped.
*With everything removed, place a drip pan under the forks and one at a time, remove the nut at the bottom of each fork leg. Remember that at this point the only thing holding the leg onto the fork tube is that nut at the bottom, so be ready to “catch” each leg as it might slide right off the fork tube! Slide the fork leg down a couple of inches which will allow the leg to drain more completely (and faster). When the draining is finished remove the fork legs one at a time by sliding it downward until it clears the damper. Place all these parts aside and out of the way.
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*At this point there should be nothing attached to the fork legs (as seen above).
*Now remove the handle bars (I used a rope over a 2×4 in the garage to hang the bars, or you could just remove the controls from the bars and get them out of the way completely. At this point you should have just the steering bearings and spring retaining nuts holding the legs and lower triple clamp in place. Remove the upper spring retaining nuts and the steering head bearing lock nut so that the top plate can be fully removed. I also removed the instrument panel to get it out of the way during this process.
Leave the steering bearing adjusting nut in place. Loosen the headlight mounting so that it is not causing any stress on the fork tubes if that is possible worth your model. It is important that the fork tubes be cleansed of any bug parts, road tar, or other debris sticking to them. If these foreign particles are where the gauge will be applied they will dramatically throw off the readings.
After cleansing them, clean your hands and slowly run them up and down the tubes to see if there are any dents or nicks on the tubes. You are checking for burrs or high edges around these nicks. If you find any, use a fine Arkansas stone to hone them down. Do so by using light pressure and working slowly, removing only the VERY SLIGHTEST amount of material in the VERY SMALLEST area possible. Burrs in certain areas can hurt the accuracy of the subsequent checks as well as damage fork seals and shorten their lives.
If you suspect that the bike may have been hit or was in an accident you will want to remove the fork tubes from the bike completely. Do this by first measuring how far they are protruding above the triple clamp (it should be 160mm).
To remove the fork tubes, first loosen the clamps on the fork yoke and remove the pinch bolt. Now use a suitable wedge like a small chisel or hard wooden wedge and carefully hammer the wedge into the slot in the yoke, opening the clamping area allowing the tubes to slide out. Repeat on the other side. Do not let them bounce off the floor!
The BMW specs call for the tubes to be within .004″ of straight, but depending on where along their length they are out .004″ can make the difference between working forks and ones that will never be made to operate properly. The Clymer manual shows the tubes being checked for straightness on a lathe with a dial indicator, but you can do it this way: Place them parallel and against each other, flat on a plate of glass and spray some WD40 or similar light lubricant on them and roll them against each other like how a pasta extruder would work. There should be no gaps. Now turn one of the legs end-for-end and repeat. If they are parallel along their entire length they are probably OK.
Whether or not you have removed the tubes, before beginning the rest of this procedure be sure that the pinch bolts on the yoke are torqued to specs. To recap- you’re bike at this point should look like the one on the previous page- forks stripped to the tubes down below and the upper fork bracket removed. Area around the bike fairly clear for action.