Forks (2007)

scim77 said:

Cash-I was interested in your note about the floating sleeve in the Covenant conversion. Am I correct in thinking that you you recommend loctiting or pinning this bush in an upermost position, rather than letting it fall down to the bottom of the slider leg, which it would otherwise do?
In it's natural bottom position it must be shielding the taper somewhat, thereby giving the harder ride you mentioned. It could also dither about with suspension movement giving varying degrees of damping resistance.

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The Covenant floating sleeve cannot "fall down to the bottom of the slider leg" as it fits above the stanchion bush on the outside of the stanchion (and below the slider bush) and does not come into contact with the damper tube taper, the sleeve acting as the forks extend and not as they compress.

I have the Covenant kit fitted, with the sleeves allowed to float, and don't have any problem with that at all.

LAB,
I'm pleased you don't have a problem, but believe me the last thing you want free floating around in the slider is that bush. If a bush sticks or bounces say half way up it may block off the holes in the stanchion and hydraulically lock the slider at the wrong moment.

There are hydraulic stops built into the Roadholder. The bottoming out stop is provided when the stanchion covers the hole in the damper tube. The topping stop is provided when the holes in the stanchion get covered by the slider bush. Because Norton reduced the front end movement the stanchion holes never get covered by the slider bush.

The Covenant kit improves the bottoming out stop by moving the damper tube hole up a little, and with that " floating"bush fixed below the slider bush provides the topping stop.
The very first Covenant kit (an early one)I fitted that bush had to be gently tapped in to the slider.

Been there got the scars etc.

Cash

cash said:

"floating bush"

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But it isn't really a 'bush' -it is a floating sleeve (unless it is fixed in the slider?).

How far below the upper bush does the sleeve need to be fixed to fully block off the stanchion holes?
If it was fixed immediately below the upper bush I doubt it would fully (or maybe even partially) cover the stanchion holes at full extension? (You will have to pardon me if I still sound a bit sceptical as to the need to fix the sleeve to the slider, but I remain a little unconvinced that this is entirely necessary)

With the early kits I fitted the sleeve was pushed home by the slider bush, ie directly underneath.

Cash

LAB,
Have a read of this its by the inventor of the Covenant Conversion.

http://www.nocnsw.org.au/forks.html
Cash

I've spent the last couple of weeks pondering these front dampers. The sleeve needs to be at least 38mm long, directly below the main bush. Any less than this & the damper rod will be the limit on fork extension. Even at 38mm (old bush with flange machined back) you need to be sure that only about 4 - 5mm of the damper rod is screwed into the top nut (the big chrome one) . (Longer sleeve would help - don,t know how long the covenant part is)

Carefull also not to put the spring top any lower than necessary as the full stroke from 'no load on spring' to 'fully coil-bound' looks to be 130mm, pretty close to the 120mm stroke I measured on my dampers.

I'm still not sure that the holes in the end of the stanchions are small eno ugh. Little evidence of damping end of travel much. If the loctite will ever let me take the dampers apart again :roll: I'd certainly try blocking one of each & see how that feels.

Same goes for the full compressed end stop - to much gap between stanchion and damper body I suspect. It did't look to me that shifing the holes from the taper to the main body would help much, but there's scope for trial & error there.

If the rain ever stops, :cry: & I can find some new tyres, I'll report back on the damper mods made so far

chris

I've got a pair of those Covenant bushes somewhere (didn't find they cured the apparently irresistable urge of Commando forks to clank on full extension). I'll have a look for them.

I've also got a nicely sectioned assembled fork leg. I'll take some photos tomorrow and see if I can find the notes that I made at the time.

cash said:

With the early kits I fitted the sleeve was pushed home by the slider bush, ie directly underneath.

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Which sounds as if the early kit sleeves were actually meant to be fixed in the slider as mentioned in the NOCNSW article?


However...

I can only quote from the Covenant fitting instructions I received with the (RGM) kit which says:
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"..........The alloy sleeve sits on the fork stanchion below the top bush. Basically being free to float. When the fork stanchion is at the position of maximum extension the oil bleed holes are covered by the sleeve this effects a type of hydraulic lock and prevents the "topping out" over rough ground which these forks are prone to. Equally it controls the front end better under racing conditions when patter can upset the steering......"

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Therefore this particular Covenant type sleeve would appear to have been designed to float?

And from the experience I've had using the kit fitted in accordance with the RGM instructions I can see no reason to change anything.

The later kit, and I assume it is, came fitted to my Commando and it gave me no end of trouble. The damping would go from soft to hard on either leg without warning, very very unpleasant. With my experience of the original concept I made a new pair of sleeves that I could fix in place. Problem solved, however I had to go from ATF to 30 oil. Is this why some systems prefer ATF?

The fitting instructions seem to contradict, "free to float" then "prevents topping out" to prevent topping the sleeves have to be just below the slider bush and if they float surely gravity would pull them down on top of the stanchion bush out of the way.

All I can say is when it went wrong for me ( usually on our poorly kept Lakeland roads ) the consequences could have been disastrous. It would be foolish not to bring it to your attention.

Cash.

cash said:

however I had to go from ATF to 30 oil. Is this why some systems prefer ATF?

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I'm not quite sure why some owners use ATF as I believe it has a somewhat lower viscosity than the recommended SAE20 oil?

I think many Roadholder fork problems experienced by owners could be cured if the specified SAE20 (or near) viscosity oil was actually used?

cash said:

The fitting instructions seem to contradict, "free to float" then "prevents topping out" to prevent topping the sleeves have to be just below the slider bush and if they float surely gravity would pull them down on top of the stanchion bush out of the way.

Click to expand...

Sorry but I disagree.

The sleeve does not have to be set just below the slider top bush to prevent topping out. For the sleeve to restrict the oil flow (on fork extension) it has to be positioned over the stanchion holes, and the stanchion holes move as the stanchion moves (obviously), which also answers your second question as the sleeves don't fall "out of the way" because if they fall to a position immediately above the stanchion bush they would then be covering the stanchion holes -adding to the rebound damping (see fastback's photo on p2).
Every fork compression stroke pressurises the oil below the sleeve and so appears to force them upwards i.e. -floating.

cash said:

It would be foolish not to bring it to your attention.

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I certainly applaud the fact that you have done so, as it has been a useful discussion and I consider that I have gained some insight regarding your experience with the Covenant kit that I have not had.

I share Cash's reservations about a "floating" bush being carried down with the stanchion. It would probably be incorrect to assume that the components remain in line in use.

My loose Covenant bushes didn't seem to help the topping out unless I used oil so thick that my 10 1/2 stone couldn't compress the forks. I also had the impression that the front end sometimes went hard and pattery (is that a word ? :? ) I have removed them.

This picture shows a sectioned fork leg at full extension (no spring, oil seal or paper washer for the purists).



Loosely placed vernier showing distance from underside of bush to bottom of bleed hole.



Image showing distance from bottom of bush to stanchion bush.




It would seem to me that the best practice would be a lengthened top bush.

79x100 said:

My loose Covenant bushes didn't seem to help the topping out

Click to expand...

But that would suggest there was a damper cap/rod wear problem (as they would be the first things to attend to if there was any topping out)? But you haven't mentioned them?

I've found that with 20 wt fork oil and good caps/rods they don't top out. YMMV.

I have one of the Covenant kits on the bench. I don't think I'll install those floating bushes. I don't see how those could work being free to float like that.

Debby

It's been an enlightening discussion so far. Photos posted by 79x100 are very helpful.

Was reading up again on some of the Covenant Conversion pros and cons, and came across this:

http://atlanticgreen.com/forks.htm

He includes a link to pictures of three different versions of the damper bodies, which I found of interest.

I'm probably going to merely stick with the "traditional" fork rebuild here and go with the 20 weight fork oil.... at least initially. Once I get the bike back on the road I'll be able to ascertain how it all works. For now, I've only to polish the other fork damper tube and it's all ready to go back together. All the parts are in and awaiting reassembly.

Was wondering, though.... anything I need to be particularly concerned about on refitting them to the bike? Are there alignment issues, for example?

wrench

L.A.B. said:

79x100 said:

My loose Covenant bushes didn't seem to help the topping out

Click to expand...

But that would suggest there was a damper cap/rod wear problem (as they would be the first things to attend to if there was any topping out)? But you haven't mentioned them?

Click to expand...

I didn't mention wear in components because I regarded it as self evident that everything be in good order before proceeding further. The newness has worn off the sectioned leg in the picture but that's because it was one that came on the bike. I subsequently built legs with all new components and fitted the Covenant kit.

I appreciate that variable tolerances in Commando fork parts can and do arise although the problem is usually one of stiction caused by tightness rather than excessive clearance. I subsequently had the chance to rebuild with all new parts again after surviving an attempt by a Peugeot driver to put me in a low-level orbit which left the pinch bolt slider embedded in the timing chest.

As I mentioned in an earlier post, I am a bit of a lightweight and thick oil causes a distinct lack of compliance at the front end. It also means that with standard parts, the forks are looking for an excuse to top out. Thick oil (which for me means 20 or above) provides too much compression damping.

The topping out problem does not occur on well surfaced roads but if the front lifts over ridges or when riding off road, It can give quite a clatter.

I had hoped that the use of the Covenant kit would enable me to use a thinner oil which would give a more compliant fork action. I have tried almost all grades of fork oil between 5 and 30. Were it not for the topping out problem, 15 would be my preference. I stand by my findings that on my bike the Covenant kit with loose bushes appeared to contribute to an inconsistent fork action.

It would seem to me to be better engineering if the conversion consisted of lengthened top bushes rather than assuming the use of original dimensions.

79x100,
Great photos and sections, they brought back a memory from the late 60s. If my memory serves me correctly I'm sure I read an article in MCN or MCW ( British weekly m/cycle papers of the time) of a couple of Roadholder breakages. The breaks were just below the slider bush with all the internals exposed.
Was this the reason for Norton fitting the short damper rod to give the sliders more support?

Cash

I haven't heard of Roadholder breakages but I was just a bit too young to be buying MCN or Motor Cycle in the late '60s (sneaking out of school on Wednesday lunchtime started a bit later !). The sliders are not as thin walled as the double cut on my sectioned leg would seem to suggest but there would be a chronic lack of overlap at full extension if the rods were any longer.

I suppose that for historical reasons we have been left with very short sliders and that a longer version would provide better support with no disadvantages that I can think of.

At least we don't suffer the breakages of AJS / Matchless forks close to the brake torque arm fixings.

79x100 said:

but there would be a chronic lack of overlap at full extension if the rods were any longer.

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It surprised me when I saw those photos just how close those bushes actually get!!

So I ripped out the fork legs yesterday which was pretty easy.

My question now is how do I get the yokes off the bike? The sliders and stanchion assembly came right out really easily but I don't want to damage anything so I'm asking here how to go about getting everything else apart.

Coco said:

My question now is how do I get the yokes off the bike?

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You should find a large thin nut on the underside of the lower yoke held with a lock washer bent down against one of the nut flats to lock it (and also bent up between two webs on the underside of the lower yoke)?

The steering stem on later Commandos is attached to the top yoke unlike earlier and many other bikes where it is normal to have the nut at the top with the stem attached to the lower yoke.

Bend the washer away from the nut, loosen and remove the nut, then tap the stem upwards with a mallet or hammer and wood block, the yokes should then come off fairly easily.

The head bearings are a sealed *ball* bearing type, these bearings cannot be adjusted, the tightness of the lower stem nut does not affect bearing adjustment.