I build the Andries van den Broek Test box in order to check and adjust the ignition timing on the 1991 K100RS.

Can anyone help me how to connect it up to the hall sensor plug that i can use it?

Or another method to adjust the timing?

Thanks Rolf

Rolf E wrote:Or another method to adjust the timing?

Line up the notches on the backing plate and the timing chain cover.  I'm sure someone will post a photo.  That will give you the factory timing which works very well.

Just line up the HES notch with the notch where it mounts:

Thanks, but I also want to advance the timing to 0.3mm BTDC to see if that will reduce the vibration on the bike.

That was one of the "fixes" suggested on another post.

Rolf E wrote:Thanks, but I also want to advance the timing to 0.3mm BTDC to see if that will reduce the vibration on the bike.

That is unlikely to help, Rolf. Changing timing usually affects power delivery and fuel economy one way or the other. If the Hall plate is on or near the notches as duck and Point-Seven-five have indicated, some other condition is causing this. It could be a failing u-joint in the drive line. If a u-joint fails, it can shatter the swing arm casting. 

Describe where you're feeling the vibration—your hands, feet, shoulders, butt.

It makes sense that changing the ignition timing will have an effect on performance and consumption, but I was just going to try it. BMW of N.A. put out formal service information in Jan 1993 giving 3 fixes. 1 Timing at 0.24mm BTDC, 2 Shimming the frame to motor and 3. changing handlebar rubber mounts. 

Riders talk of the K Buzz and I feel it in the hands. Since I have K-pox I am on a mission to find or at least reduce the vibration. After 50km on the bike the hands get pins & needles. I test rode a K1100LT the other day with only 27000km and the tank was vibrating at a certain rpm.

I have used our SKF Microlog, taken vibration readings and think that we are dealing with resonance caused by some source vibration. It is not speed related but rpm related and the frame goes into resonance. So I doubt the problem is in the drive train. I still need to do some of vibration measurements at various locations. The exhaust especially. Just touching it lightly with the finger, there is no question that there is resonance. No 4 header pipe was also cracked where it attaches to the branch.

The cracked exhaust header because of harmonics is a common problem. The fix is two big jubilee clips (worm drives); one where the four pipes enter the exhaust and one some three-four inches ahead of the collector box. Some people use two worm drives and some use one; in both cases it is the one that is three-four inches ahead of the collector that kills the harmonics and stops the cracking.

In my experience with many Ks, keeping the throttle bodies sync'd helps reduce vibration.

Thanks guys. Yip I am sure the clamps have helped. I welded a S/Steel strip right around the header pipes, to act as a clamp, more or less at the same location. That will interfere with the individual harmonics and resonant frequencies. I think it did make a difference, but not enough.

My next step is, testing where on the exhaust the the maximum amplitude is and then by trial and error adding dynamic mass dampers...??

Rolf E wrote:BMW of N.A. put out formal service information in Jan 1993 giving 3 fixes. 1 Timing at 0.24mm BTDC, 2 Shimming the frame to motor and 3. changing handlebar rubber mounts. 

Riders talk of the K Buzz and I feel it in the hands. . . .  After 50km on the bike the hands get pins & needles.

So I doubt the problem is in the drive train.

Now that you've finally described the effects, I doubt it, too. 

0.24mm BTDC is the shop manual specification for timing—nothing special there. If the notches align, you should close enough but doing a by-the-book check can be comforting sometimes.


I'm going to go with handlebar mounts or frame shimming as being the culprits but I can see the attraction of hunting for rogue resonance.

I'm with Laitch on frame shimming and/or handlbar rubber mounts. The frames were so bad that the factory recommended bolting up the gearbox first and then shimming the front of the frame to take the gaps out. I've recently replaced the handlebar mounts in my '83 bike (LFB - Low Flying Brick) and that did make a difference. The forty years old ones were cracked and starting to fall apart.

[Edit] Why is it that every time I use the word 'rubbers' I feel the urge to go back and edit my post?

Check your throttle body balance but before you do that be sure your valve clearances are good.

Your injectors should also be good.

Something that I found made a very big difference, new footrest rubbers.

If you have doubts about your frame mounting points check them. They should be shimmed to take up all gaps before bolting up the mounts. You will need to slacken them all to do this. The mounting bolts must not be used to pull the engine and frame together, if you do that you are pre loading the frame with stresses. That's why they need to be correctly shimmed. Its easy during maintenance for shims to get lost.

Frame mounting is described on 6-42 of the BMW manual.

Page 186 of this PDF:
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/shopmanuals/BMW_K1_K100RS4V_Repair_Manual.pdf

I am overwhelmed at the experience and willingness to help from all of you. Thank you very much!!

As I said, I am on a mission and will look at everything and that is why I also want to make sure the timing is 100% and then what effect a change has.

Some of us just need to be kept busy . . . for all sorts of reasons. 

I found what I was looking for on the tech page.