knock in forks

[williamemack]

I'm finally getting some of the issues with my "new" R65 sorted out, but one last item is hiding in the front forks. It's a knock really, most noticeable at low speeds and, at one time, I thought it occurred on rebound rather on compression. I pretty well have determined that it is not coming from elsewhere as I have taken the instrument cluster apart, emptied the tool tray, held onto the gas tank during a knock (couldn't feel it in the tank), checked brake disc and caliper, fender mounts, etc. I do not feel this knock in the handlebars, but it is definately coming from the fcront end.Anybody got any ideas as to what could be causing this? Two dealers have suggested a fork rebuild, but the odo on this bike only shows 19,000 some miles. No, I haven't checked oil viscosity or level yet.

Thanks for any ideas you might offer.

[nhmaf]

I'd just make plans on the weekend to at least take the tops of the forks tubes off and pull the springs out, drain the oil, and depending on how it looks,
 decide whether or not to continue disassembly of removing the wheel and sliders.  They could be low on oil, the spring might be damaged, there is (or should be) some dark plastic or rubber bumper that resides down low in the fork assembly that often disintegrates, which could cause the spring to be extending farther than normal.  OR, someone might have put in new springs and not enough oil.  Or, I know that the progressive springs, which are a popular aftermarket change, come with a PVC "spacer" to provide the proper amount of preload in the R65 forks.   IF the PO put the spacer on the top of the spring (top of the fork) this can end up causing more noise in the fork tube than if the spacer was placed at the bottom of the spring/tube.

Have you checked the front wheel (axle nut and pinch bolts) for proper tightness and to see if there is any wheel bearing play ?   I guess I'd do this first, as well as checking for play in steering head bearings before fork disassembly... "Check the easy stuff first!" is my credo these days...

[montmil]

A short time ago, I also thought my front forks were needing attention, even though I had just completed a seal and wiper replacement, interior cleaning and "correct" BMW-branded fork oil (7.5 Wt) re-fill.

Still heard/felt a "knock" on occasion so considered trying different fork oil weights. Rebound and compression were common knock-knocks.

Well, she don't knock no mo'. This may not be anywhere close to your issue but I found one of my centerstand retraction springs had gone missing. Replaced the spring so that we now have the proper two springs and... the knock/clunk went away as the centerstand stays snugged up and no longer knocks against the frame. Go figure.

That's my story and I'm stickin' to it.

Monte

[williamemack]

Thanks, Monte. My center stand springs are fine, but I'm unsure about whether they seat against a proper, non metallic stop. I'll slip a piece of rubber in there tomorrow and see if the knock goes away.

[williamemack]

I corresponded with another forum member, Barry, who said 79/80 R65s tended to have a clonk due to a lack of a shim to eliminate end float in the valve body, OR decomposition of the rubber bump stops at full extension. Has anyone found a fix for this or has tried to use a R80 valve body set up?

[Barry]

Will

Sorry I didn't explain properly about the topping out bushes.  They didn't break down just went very hard with nothing like enough resilience to bring the forks to gentle halt at full extension.  The replacements from Motobins were softer but still not soft enough which is why I think I should have replaced them with the short springs fitted to the R80ST.  This mod should work as the 80ST forks are the same as ours except for a different top nut arrangement and a spring instead of a bush to control topping out.  My forks are not too bad now so I won't do this until I next need to change the fork oil.

The original design of the 79/80 forks is so poor I do have a hard time believing that everyone has silent forks except you and me. Anyone else tackled this problem?

Barry

[williamemack]

Thanks, Barry. Frankly I feel a lot happier with my forks knowing that my clank is par for the course.  I may just cool it for a year as I feel most repair shops are not going to want to bother with sorting this problem out.You have my email address. If you ever try the springs from the R80, let me know how it works out.

Cheers,

Will

[Semper Gumby]

Mine clank as well whenthe going gets rough.  I am just used to it.  Now if I could find a decent R100GS front end for the bike I would jump on it.....

[DgM]

I get the fork clunk when putting bike on or off centerstand, no clunk while riding.  Mostly forks spend their time diving during braking.

[williamemack]

OK, took the bike in to Duncan's Beemers today and they stripped the forks, added spacers, replaced the rubber top out bumpers, replaced seals and put it all back together. On the short trip home..no clank. I'll keep my fingers crossed.

Will

[nhmaf]

Good to hear !

How is Duncan's for doing business with ?   I live up in NH and have sometimes seen among his used bikes for sale an airhead or two that caught my eye.

[williamemack]

Update....sorry to report the knock is still there. There's gotta be someone out there in R65 land who has found out how to six this knock.

Merry Christmas all.

Will

[Ed Miller]

I don't suppose it could be a brake line or something whacking against your fender?  Mine doesn't do it.

[williamemack]

THanks for the reply Ed. One day, I took a rubber mallet and wacked mthe front end in various places in an attempt to reproduce the klonk, but with no luck. I also checked cengter stand, in and around the headlight and tightened all fasteners. Still at it!

Will

[montmil]

...Still at it! Will

Have you tried a heavier weight fork oil?

Monte