Clunking forks

Started by The Prophet of Doom, March 07, 2009, 08:48:03 AM

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The Prophet of Doom

Before I strip my forks down again, does anyone have any suggestions?

When I am riding, every time I hit a bump, I get a clunk sound, a bit like the fork inner is not attached, and is jumping off the bottom and then reconnecting.  There is a slight metal on metal feeling through the grips.    When I hit chatter bumps there is a floaty feeling and a distinct rattle.  It gets very disconcerting and doesn't feel at all safe.

When I dive the suspension it clicks - a different sound than while riding, but also not right.  It's hard to pinpoint the exact location of the sound, but sounds lmost like the fork lowers.  I've checked the bottom bolts and they are nice and tight, no seal leakage, triple tree tight, no movement in wheel bearings, or steering head.  Double checked all bolts for tightness.

It never made these sounds before I did extensive work to the front end.  I have replaced steering head bearings, braided brake lines and added a full fairing, new fork seals and oil (249cc, 15wt Yamalube fork oil) 249cc because it's a Euro version 82 with stock progressives and no air.  15wy because I couldn't find 10w30 fork oil.


Night Vision

Euro version 82 with stock progressives  ??

I have progressive aftermarket springs in my US 82.... somethimes they "click" almost clunk
I guess they made them sightly small in diameter.

put the bike on the centerstand and raise the front wheel...... any forward aft / action?
if it ain't worth doing it the hard way....
it ain't worth doing it at all - Man Law
;D


if it ain't broke..... take it apart and find out why


don't give up.... don't ever give up - Jimmy Valvano

Rick G

I installed tapered roller steering head bearings in 2003. In 2004 while riding to Oatman it developed a clunk on bumps , uneven pavement and while stopping. A carefull examination revealed that the steering head rollers had worked loose. I managed to find  a drift and hammer in Oatman and tightened it enough to get home.The point is that  your problem sounds like loose steering head bearings. Do you still have the factory loose ball bearings ? They have a tenancy to pound  and dent the races , which will cause the symptoms you describe.
Rick G
Go soothingly on the grease mud, as there in lurks the skid demon
'82.5 Yamaha XZ550 RJ  Vision,
'90 Suzuki VX800, 1990 Suzuki DR350.
'74  XL350   Honda , 77 XL350 Honda, 78 XL350 Honda, '82 XT 200 Yamaha, '67 Yamaha YG1TK, 80cc trail bike

inanecathode

How's your head bearings dude? I'd get the front end off the ground and jerk it around and see what moves.
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jefferson

There is a good chance that your upper triple clamp is not tight on the stem. For some reason our upper clamps don't bolt tight to the stem like most. The lugs are there, but the machining wasn't done to put the bolt through etc. Loosen your top clamp at the forks and the stem nut, then tighten the stem nut first and then the forks. That may take care of the clunk. If not you might look into some shim material around the stem.

Jeff

jasonm.

I had clunks as well. YES plural..clunks. First my new tapered head bearings I had not tightend enough. SO I tighted more. That clunk...gone. Then the other is inside the forks as Nightvision describes. My stock '83 springs do it and the Progressive brand does it worse.  I measure them. The Progressives are at least 1mm narrower diameter. Thus the progressives sit in a box.  I use 0w30 Mobil1 in the forks. FLipping the forks "upside down" per the manual. With the tighter coils at the bottom helps slightly. They say these are the coils that are softer and compress first.  But my thought is the heavier coils cause the spring to bow...which is natural.
looks aren't important, if she lets you play by your rules

Rick G

Hi Jeff, I tried to email you at JLSracing, but it bounced , do you have a new one?
Rick G
Go soothingly on the grease mud, as there in lurks the skid demon
'82.5 Yamaha XZ550 RJ  Vision,
'90 Suzuki VX800, 1990 Suzuki DR350.
'74  XL350   Honda , 77 XL350 Honda, 78 XL350 Honda, '82 XT 200 Yamaha, '67 Yamaha YG1TK, 80cc trail bike

The Prophet of Doom

I've double checked the fluid levels, triple and all other bolts, including the steering head (tapered bearings).  I even swapped out the caipers in case they were making the noise. Also rotated the springs.
I guess I'll be pulling the forks apart again in the weekend :-( sigh

Night Vision

check to see if the bushings on top of the dampner rod are worn while you're in there
if it ain't worth doing it the hard way....
it ain't worth doing it at all - Man Law
;D


if it ain't broke..... take it apart and find out why


don't give up.... don't ever give up - Jimmy Valvano

motoracer8

  In the early and mid 80's Yamaha had some issues with too much clearence in the fork sliders on some of their machines, I have a service buliton somewhere if I can find it. Ventures, and some Seca's had the probblem, I don't know if Visions were in the group. Not all of the bikes had the probblem. But when you applied the front brake you would feel a click or clunk in the bars, sometimes you could hear it. Or if you went over small bumps like rail road tracks.  The fix was to replace the sliders, as they have no replacement bushings.

   Ken G.
83 Vision and 11 others, Japanese, German and British

The Prophet of Doom

I think this is a new clunk, although it could have been masked by the really bad steering head bearings.  I suspect something has broken, or been assembled wrong by me, rather than a birth defect.

NV  I will check the bushings on the damper rod, what should I look for.?

Night Vision

I would inspect them for signs of obvious unusual wear (oblong or cracked, loose etc.) check to make sure you don't have any noticable slop/back and forth movement...

like M8 said, there are no replacement parts, you can't just get the nylon bushings
if it ain't worth doing it the hard way....
it ain't worth doing it at all - Man Law
;D


if it ain't broke..... take it apart and find out why


don't give up.... don't ever give up - Jimmy Valvano

The Prophet of Doom

Well I pulled them apart, and figured out what was wrong.

Turns out the clunk was the fork getting near to bottoming out  When I screwed them up, the fork inner can't have been all the way down, and so the aluminium bush didn't quite line up.  This is called "spindle taper" in the US 82/83 parts lists, but this is a euro spec bike with factory progressives and it isn't tapered at all.  Every time the forks came within an inch of bottom it went clunk as the inner found its way over the bushing.

What I had forgotten is the forks were setup was designed for (and last ridden as) a nekkid bike.  Now that I have a full factory fairing that's a good number of extra kg sitting right over the forks.  Not to mention that I weigh more than your average Japanese test rider. 

I put in 1 1/2 inch longer spacers.  Static is down from 5.5cm to 2.5cm.  250ml 10W30 oil as per Haynes and all is sweet.  There's still a tick on full compression, but that doesn't happen often, and it should go away as the bushing wears.




YellowJacket!

Hmm...was rolling mine around without a helmet and the engine off and I heard a clunk too.  Will have to investigate.

David


Living the dream - I am now a Physician Assistant!!   :-)