Front end clunk

[barney]

I`m the happy new owner of a 1985 K100RS.I appologize if this has been discussed here before but my search came up empty.When riding slowly on rough ground I hear a clunking noise from the front end.I`m able to duplicate this noise somewhat by rocking back and forth on the centerstand and their is no play that I can find in the steering head.The noise appears to be coming from the forks so I changed the fork oil but still hear the clunk.Any help is much appreciated.

[Bruce_C]

Barney
The steering head bearings are loose and also need to be lubed.
Bruce C

[deilenberger]

I`m the happy new owner of a 1985 K100RS.I appologize if this has been discussed here before but my search came up empty.When riding slowly on rough ground I hear a clunking noise from the front end.I`m able to duplicate this noise somewhat by rocking back and forth on the centerstand and their is no play that I can find in the steering head.The noise appears to be coming from the forks so I changed the fork oil but still hear the clunk.Any help is much appreciated.
It's certainly worth checking the steering head bearings - to do this the front end has to be in the air (a floor jack under the engine works). Turn the bars from side to side. If you feel any roughness the bearings are KAPUT (tech-term for DEAD..) and have to be replaced. If the bars turn with no resistance at all - the bearings made need adjusting (which you many want a dealer to do if you're not comfortable playing with a critical component on your bike.

The other possibility - the early forks DID sometimes have a clunk in them. This was due to slightly greater than desired clearances. BMW has shims that can be used to get rid of the clunk. Installing these requires disassembly of the forks - again - if you're not comfortable..

[jibimy]

Check the cam drive chain.

[barney]

Thanks everyone for the replies.With the front end elevated,the bearings turn smooth and I detect no movement or noise when I push/pull on the stancions.The noise is coming from the fork legs and I can duplicate by extending/compressing the forks near the travel full extension.I`m comfortable servicing the forks so if someone can elaborate on the shim procedure I`ll give it a try.Also will heavier oil reduce the tendency to dive under braking and possibly mask the clunk?Currently have 5w Honda suspension oil in the forks.

Btw,
I put 344 miles on the bike yesterday and had a blast!!!This bike loves to cruise along at 80.I think I will adapt to the buzz.

[deilenberger]

Thanks everyone for the replies.With the front end elevated,the bearings turn smooth and I detect no movement or noise when I push/pull on the stancions.The noise is coming from the fork legs and I can duplicate by extending/compressing the forks near the travel full extension.I`m comfortable servicing the forks so if someone can elaborate on the shim procedure I`ll give it a try.
What service manuals do you have? If none - I'd suggest getting at least one.

Also will heavier oil reduce the tendency to dive under braking and possibly mask the clunk?Currently have 5w Honda suspension oil in the forks.
YES and no. It will slow down the dive under braking, but with enough time/force on the brakes you will dive the same amount. It may initially appear to have reduced the dive - but it really didn't.

Damping (what the oil does) only "damps" the movement - it doesn't control the range of the movement.

The '85 K had a very long travel front suspension. This was good for comfort - but not so good for handling. Starting in '86 the K75S introduced the "Sport" forks, which eventually made their way over to the K100 series (I believe first on the '88 K100RS.) These forks have less travel, and less dive. They used a two-part spring (with two compression rates), slightly different damping settings and a fork-bridge between the two legs (helps to resist twisting of the legs.)

To reduce dive in your K100 - the best route is a set of aftermarket springs. I'd suggest Works Performance springs - good value for the $$$ and fairly easy to tune.

Putting a heavier oil in your forks will result in higher compression damping, which will also result in a harsher ride.


Btw,
I put 344 miles on the bike yesterday and had a blast!!!This bike loves to cruise along at 80.I think I will adapt to the buzz.
Luckily - 80 indicated is usually only about 73-75 real MPH (GPS measured) helping to keep your license intact. The sweet spot is at 80MPH/5,000 RPM for the '85 RT. The buzz can be helped a bit with foam grips and gel-palm gloves, but after a while - it always started causing me pain in my hands and eventual numbness. I cured this by buying a K75S.

Best,

[Bruce_C]

Thanks everyone for the replies.With the front end elevated,the bearings turn smooth and I detect no movement or noise when I push/pull on the stancions.The noise is coming from the fork legs and I can duplicate by extending/compressing the forks near the travel full extension.I`m comfortable servicing the forks so if someone can elaborate on the shim procedure I`ll give it a try.Also will heavier oil reduce the tendency to dive under braking and possibly mask the clunk?Currently have 5w Honda suspension oil in the forks.

Btw,
I put 344 miles on the bike yesterday and had a blast!!!This bike loves to cruise along at 80.I think I will adapt to the buzz.


Barney
I like a firm ride on my '85 K100RT. I use 370cc.of 15wt. fork oil per leg. That's 10cc. over spec., but still allowable according to my Haynes manual.
Bruce C

[deilenberger]

Barney
I like a firm ride on my '85 K100RT. I use 370cc.of 15wt. fork oil per leg. That's 10cc. over spec., but still allowable according to my Haynes manual.
Bruce CMore oil results in a stiffer "air-spring" (the air above the oil in the forks works just like a spring, and neat thing is - it's a progressive spring.) More oil will make things "firmer" and may reduce dive at the same time, but it's not possible to have two different response curves with a cross-over point just using air.

The reason I like the Works springs (which I'm using on the S - about the 3rd set I've had on various bikes..) is - their adjustment allows you to determine how much soft-dive there is before the forks transition to the stiffer spring. Tuning the forks this way you can adjust them for good compliance over sharp/small bumps with good control over longer bigger bumps.

Best,

[barney]

Plush on the small stuff and good bottoming resistance,just the way I like it on my dirt bike.At $109 I may try a set of Works springs.

[barney]

Well I finally got around to replacing the fork springs with a set from Works Performance.BIG difference and much happier!Thanks for the advice.