Wobbling handlebars - k75s 1993

I read in another thread that a bad wobble could be attributed to steering bearings or the fluid-bloc.

The issue is that when I let go the handlebars (please don't ask why I let go the handlebars), or only one handlebar, for just a few seconds, say to tighten the cruise control screw under the righthand handlebar, I get a wobble that worsens exponentially at the handlebars. The bike has 45,000 miles (76,000km). It did not wobble when I purchased it a few years ago. It was steady as on rails when I let go my handlebars. As a matter of fact, all my BMWs where steady when I let go the handlebars for a few seconds at a time.

I do remember that at one point I removed the front fairing and the support that holds the front fairing. I may have unscrewed the screws hold steady the fluid-bloc. I don't even know what that systems actually does. There is very little information about the mysterious fluid bloc. Is it some kind of steering damper? Because that could explain some wobbling or shaking.

Would adding risers and C-bars on my S be cause for shaking?

Anyways, I know something is fishy there and it is not getting better with time. It definitely needs attention.

Ghyber

The fluid bloc is indeed a damper that was added to the K75 because it has less weight on the front tire than the K100. Essentially, it is a rubber cylinder that surrounds the triple tree stem inside the frame tube. It is coated with a thick silicon grease and secured by 2 grub screws. If you had two pointy allen heads left over, or used flat allen heads, the fluid bloc will rotate with the steering stem and provide no resistance, which could very well could be you problem. On the S, the grub screws also hold the top of the fairing support to the frame tube, they are the ones circled here: (I doubt the risers or C-bars would cause wobble, I've had both with no issues)

My 91 75RT would wobble when the Metzler wore about 50%. It does not wobble with the Bridgestone Spitfire.

There are a bunch of things that can cause the wobble.

Misaligned forks, bad tire, loose steering bearings, bad wheel bearings... Even stuff further back like frame bolts and swing arm bearings can be culprits.

I had a wobble at about 45-55mph for the first year I owned my K75. I've done a lot of work to the bike since then so i don't know what fixed it but it's gone.

It is easy to see if your steering head bearings are bad. Put it on the center stand and have someone put weight on the rear of the bike so the front wheel is off of the ground. Slowly turn the handle bars and try to feel a slight detent when the bars are straight. If you can feel this little bump whenever you go past center. then the bearing are bad. The bars should go from side to side easily by their own weight , but not flop. If they flop. then tighten them up. I hope this solves your problem.

35634 said:

The fluid bloc is indeed a damper that was added to the K75 because it has less weight on the front tire than the K100. Essentially, it is a rubber cylinder that surrounds the triple tree stem inside the frame tube. It is coated with a thick silicon grease and secured by 2 grub screws. If you had two pointy allen heads left over, or used flat allen heads, the fluid bloc will rotate with the steering stem and provide no resistance, which could very well could be you problem. On the S, the grub screws also hold the top of the fairing support to the frame tube, they are the ones circled here: (I doubt the risers or C-bars would cause wobble, I've had both with no issues)

Click to expand...

Thanks for the inputs.

I am aware that there may be many variables, e.g. unbalanced front wheel, badly or poorly worn front tire, worn or loose steering heads, fluid bloc, uneven fork oil, worn fork springs, etc...

However, I can eliminate many of those such as tire, balancing, fork springs and rear schock and after reading "leftturn's" input, the steering bearings as I have replaced many of these parts already.

I think I may have messed-up with the fluid bloc system when I was removing the front fairing and that is where I will concentrate my attention. However, I did read in another thread where a fellow rider and poster, I believe it is "Lee", mentions that the BMW grease for the fluid bloc has not been available from BMW for years. Are there any replacement greases for this part?

Ghyber

a little info on the fluidblock...http://www.ibmwr.org/ktech/fluidbloc.shtml

Corning High Vacuum Silicon Grease 976V, also known as stopcock grease, is an acceptable substitute. Does not take much, this 1oz container would be plenty..
http://compare.ebay.com/like/280617417916?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar

Just a quick check, pull out the hex screws circled in the picture and see if the end is pointed. If it's flat, you got the wrong screw in there and It's not holding the fluidblock.

As noted above, you would benefit from raising the front and testing its 'flop' from side to side. My understanding is that if your bearings are dented, this would likely act as bearings that are too tight and provide a long duration weave as opposed to a short duration wobble. Wobble in the front, as I understand it, would mean a loose steering head bearing, or, as you are thinking, a lack of proper damping of the steering head motion. I am not sure about the fluid block functionality, but most steering dampers are intended to provide high speed stability and are not really functional in the 40-45mph range. This is the test range I was told to use to determine if the steering head bearings on both my '85 and '93 RSs were loose. When I had this issue and eliminated the the tires from the equation, tightening the steering head bearings was my solution.