I've just dismantled my forks on my 1972 Commando as they were ratting a bit.
1. The collar seems different from what I see available - my one has a rubber seal and o-ring inserted into it. The o-ring came out but I couldn't get the seal out. Is this seal redundant given the one below it? See pictures.
2. There were bits of a previous rubber seal at the foot of each fork slider and a different size washer inside each - one had a large fibre washer, the other a smaller metal washer. It looks like there was a rubber seal under or over the washers. See photo. According to the drawings there should only be a fibre seal.
3. How bad does the scoring on the stanchions have to be before I should consider new ones? See photo
Thanks for any advice
Looks like someone has made…
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What about the collar?
Yes, just ordered new stanchions.
Can anyone comment on the collar with the built-in seal and o-ring? I don't see any such item available now. Should I just reuse them?
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There's a strong "emergency…
There's a strong "emergency engineering" vibe about these pix.
You might take a look at the Mick Hemmings (r.i.p.) fork overhaul video, available from the NOC shop (also covers brakes and wheels) for general insight.
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Was not aware of that video…
Was not aware of that video. Duly purchased and awaiting delivery now. Thanks
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I've never seen the…
I've never seen the retaining collar modified to accept a seal. My guess would be that someone had a lathe and an idea. The collars will still do the originally intended job and be a bit lighter too. I wouldn't run the additional seals in the collar as well as the standard seal because it will introduce more stiction.
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Fixing the full extension clunk
So I got my new stanchions, bushes, Mick Hemmings video, etc. and rebuilt the forks. I thought this would stop the metallic clunk when the forks extend fully, but no. I checked the oil - I had put in 150cl of 5W-20 but changed that to 180cl of SAE 20W. Didn't make any difference.
I've since read a lot about this clunk being a design fault, and various solutions. The simplest seems to be using an extended upper bush but that begs the question: doesn't that just mean I get a clunk from the lower steel bush hitting the upper bronze bush before the damping tube tops out?
I don't feel capable of other solutions like blanking off holes and drilling new holes in the damper tubes.
Or do I just live with clunk? I won't be going off-road..
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I did both the Covenant…
I did both the Covenant conversion and the longer bushes. No clunk at either end of travel.
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Me Too
I did the Covenant mod and the longer bushes.
Worked very well, which makes me wonder.
If it was such a simple fix, why didn't the factory do it?
They had teams of blokes in the drawing office, what were they doing most of the time? Drinking tea?
Don Anson
Melbourne Australia
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Mick Hemmings shows a damper…
Mick Hemmings shows a damper rod extension a few cm long in the video but I can't see that anywhere for sale. Seems that will that simply compress the spring more? With what result?
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I'd put up with the clunk -…
I'd put up with the clunk - it's only noticeable when you put the bike on the centre stand. Just use the side-stand when someone's watching :)
The idea of the longer top bushes is that there's a hydraulic lock before the lower bush hits. The one's from RGM do more or less get rid of it.
Roadholder forks have bigger problems than that clunk when compared to a more modern design. I recommend speaking to Maxton ( https://www.maxtonsuspension.co.uk ) who can update them.
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After the modifications my…
After the modifications my clunk free forks do feel less responsive to the bumps and i suspect that some experimentation with oil grades and quantity may be needed to improve matters.
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Damper cap/bush
The damper aluminium top bushes are often forgotten about, usually wear out quickly and can be a cause of poor damping and extension clonk. RGM have a cast iron version that lasts for ever. I fitted a pair near on 50000 miles ago and still no clonk. They took a little time to bed in but well worth it.
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Those interested in…
Those interested in experimenting with fork oil grades will want to study this site:
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Looks like someone has made some 'improvements'. I've never felt the need to move away from the standard setup with regard to sealing performance.
Those stanchions are knackered. Maybe the mod was to move the oil seal away from the worn area.