The short Roadholder forks on my '55 Model 88 are very stiff. They feel as though the damping is way too hard on compression. I am using 20W fork oil, and from memory I measured 190ml.
The forks are re-bushed and almost standard - the damper tubes are alloy (I have read that this was only fitted to Manx), and the top caps on the damper tubes was bushed a while back. They were well worn, and a local machinist decided to bush them rather than fabricate the item from scratch (not available in NZ at the time). They are a fairly close running clearance.
What should the clearance between damper tube top cap be? I realise that this will affect the damping rate in the forks.
On a parallel tack, there is a fork bush and damper tube modification developed in the USA, but I can't remember what it's called. Someone please remind me, and comments about its benefits appreciated.
Paul
It is impossible to know…
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It is impossible to know from you post whether it is damping or stiffness, I don't know if this is something that just started with a fork rebuild or what, but FWIW I have never rebushed a set of Norton forks where the stanchions were new that I didn't need to take 2 or 3 thou off the inside of the upper bush before they were a running fit.
What I would suggest:-
With the bike on centre-stand, slacken the top nuts until the springs pop out, then pull the wheel up manually, it should come fairly easily, but if still tight, drain the oil and repeat, then if still tight slacken the wheel spindle and pinch-bolts and repeat, this should tell you if it is too heavy (e.g. sidecar ) fork springs, tight bushes, excessive compression damping or misalignment.
Good luck!