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Old 08-30-2008, 07:22 PM   #1
bikerlt OP
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My '83 R65 Front 'clunk' over potholes. Driving me CRAZY

If someone can help me solve this mystery you'll be a real hero.

The guy I bought the bike from was so irritated with high speed wobblies that he had the steering head bearings replaced, and put a fork brace on, and put progressive springs in within the first couple of thousand miles. He said it didn't help much. I noticed it when new to the bike, but have adapted to it so well, apparently, as a rider that I actually haven't experienced it in years.

What DOES drive me insane is a 'clunk' in the front end every time I hit rail crossings, pot holes, or go off of low curbs. I've tightened the steering head bearings down to excess for a short test drive, and it's unaffected. I've ridden without the brake caliper installed (for a very short ride) and the noise/clunk was still there. I've rebuilt the forks twice from bottom to top just to make ABSOLUTELY certain that all parts were there and assembled correctly. Still the same clunk. Rode without the gastank... still clunk.

I've read every post in advrider with the work 'clunk' or 'clunking' in it. No stone left unturned.

I wonder perhaps after all this, if those aftermarket progressive springs may be too stiff?
I weigh 155 lbs, and this just may be the sound of the forks bottoming when the bike gets 'unsprung' while riding. If I'm not compressing them enough with my weight, perhaps they're bottoming more easily/frequently than they should? Even so, they shouldn't make a metallic 'clunk' when bottoming should they? Shouldn't the fluid and valve keep them from rebounding so fast? Is there some sort of cushion I could install that is not pictured in any of the exploded views I've referred to in the manuals?

I've had this bike for almost twenty years and it's like part of the family. This has been the only constant irritation and that's a damn shame. The BMW mechanics I've brought it too have been unhelpful.

Anyone else ever suffered this malady?

bikerlt screwed with this post 08-30-2008 at 07:36 PM
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Old 08-30-2008, 08:41 PM   #2
bpeckm
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Not sure of the R65 fork, but the /6 forks have a nylon or plastic donut that helps when the forks top out. The parts schematic was quite un-specific about where it was to be placed, so I had a hard time with mine until I sought "professional help">

There are two nylon donuts: one is at the very bottom of the slider, and its purpose is to absorb any bottoming out. The other one is actually at the bottom of the tube, so that the slider will hit it as it goes down, "topping out".

You say you have rebuilt... are you sure that those two pieces are at the correct place....?
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Old 08-31-2008, 06:30 PM   #3
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Welcome to the club. This is a most common complaint about airhead front ends (my R80 ST does it too). Lots of folks seem to have traced it to one thing or another, but most have not.

Run some searches in this forum using keywords like airhead clunk, clank, front suspension noise, and so on to find the relevant threads.

So far, my best guess on my bike comes down to the upper triple clamp (that stamped steel abomination) having slop around the steering stem or the fork tubes, or the entire instrument bracket bouncing on the bumps.

Other popular theories include the springs hittng the insode of the forks and bump stops at the ends of springs disintegrating with age.
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Old 08-31-2008, 06:44 PM   #4
BillsR100
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Quote:
Originally Posted by mark1305
......So far, my best guess on my bike comes down to the upper triple clamp (that stamped steel abomination) having slop around the steering stem......
+1 That what it is on my R100.
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Old 08-31-2008, 06:56 PM   #5
Uncle Ernie
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Mine did it too. I just forgot about it.
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Old 08-31-2008, 09:25 PM   #6
bikerlt OP
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I've got wonderfully beefy cast aluminum triple clamps ('83 model year). I've tightened everything conceiveable. I wouldn't have admitted to anything so extreme/stupid, but the spring slapping suggestion compels me.... I even wrapped the springs in innertube the first time I rebuilt the forks. It did nothing except absorb fork oil and expand, pretty much jamming up the works. But it did not do anything to fix the clunk.

I'm fairly convinced by now that it is a problem with the valving and cushions (or lack of cushions) inside the fork assembly. I just have to figure out how to put some sort of cushion in it.
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Old 08-31-2008, 09:37 PM   #7
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My R100 clunked for over ten years like that. I never did figure it out...
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Old 09-01-2008, 07:36 PM   #8
bikerlt OP
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Unfortunately I just can't seem able to tune it out of my head. Everytime it clunks it raises my blood pressure. I'm not generally neurotic, but this thing has just defeated me.

I'll rebuild the forks (a third time) and see about putting some cushioning inside so that it doesn't do the mechanical slap on rebound.

I'll let y'all know how it turns out.
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Old 09-01-2008, 10:01 PM   #9
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Without looking at diagrams I believe there's no cushion when they're at full extension. You said compression - but fully bottomed out isn't the problem - it's when they're fully extended. Right?

There were things called 'bottoming springs' but I'm not at all sure they were for the newer style forks, or just the earlier ones with the Ate brakes.

If you've got stiffer springs in there, you'll need to run stiffer oil as well to dampen the greater rebound forces.

As for the wobbles, Duane Ausherman has a bit to say on that. He says it all has to do with fork tubes being absolutely parallel - and gives data on how to check and how to fix. Check out his site - a lot of great data there.
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Old 09-02-2008, 02:02 PM   #10
Airhead Wrangler
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Like Mark said, welcome to the club. I haven't sorted mine out yet, but my money's on those plastic bumpers. I have it on good authority from a local airhead guru that those things get eaten away by fork oil and disintegrate completely. Anyway, here's a thread I started about this back in may. Not a whole lot of definitive answers, but plenty of starting points. Enjoy:

http://www.advrider.com/forums/showthread.php?t=341433
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Old 09-02-2008, 02:44 PM   #11
bpeckm
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Quote:
Originally Posted by Airhead Wrangler
Like Mark said, welcome to the club. I haven't sorted mine out yet, but my money's on those plastic bumpers. I have it on good authority from a local airhead guru that those things get eaten away by fork oil and disintegrate completely. Anyway, here's a thread I started about this back in may. Not a whole lot of definitive answers, but plenty of starting points. Enjoy:

http://www.advrider.com/forums/showthread.php?t=341433
I can vouch for that: when I took my forks apart, there was sludge in the bottom of the sliders, and no bumpers to be found anywhere.... took me a while to figure out just where the bumpers were supposed to go, upon rebuild!
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Old 09-02-2008, 04:05 PM   #12
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Lose that clunking!

There is a BMW update that will fix the clunking. I have done this on my 81 R100CS and have had great results. I am not sure if will work on an R65 though (though it certainly looks like it will!). This is basically a factory anti-dive kit upgrade.

You remove spacer BMW PN#31422301016, and replace it with BMW PN#'s 31422301885, 31421241665, and 31422301886. This job can be a PITA to do if you don't have the official tool, but I made something that made it much easier.

Go to MAX BMW and check it out on the fiche!

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Old 09-02-2008, 04:28 PM   #13
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Translation...

Put in #'s 11, 20 and 21 to make your forks looks like the very right side, and not the next column to the left (I think...)


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Old 09-02-2008, 08:13 PM   #14
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Solo Lobo,

Great pic! Thanks, I would have done that myself, but I was at work.

Close, take out #14 and replace it with #11, #19, and #20. ALso this is only for the 1981 - 1984 forks.

Phack


Quote:
Originally Posted by SOLO LOBO
Translation...

Put in #'s 11, 20 and 21 to make your forks looks like the very right side, and not the next column to the left (I think...)


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Old 09-02-2008, 10:58 PM   #15
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I too have the clunk-monster. Hitting a bump while braking, really brings it to life! I think I will try that kit described above.
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