Dear All, Can some tell me or point to where I might find the length of the stanchion, damper rod, damper tube and slider of the various Roadholder forks? The roadholders on my Norvin seem to have very little stroke and it may be that I have mixed components. Thanks.
You can read tons of articles and they all say different things about Norton/AMC forks in general. Some articles talk about the length of the damper tubes and others about length of the damper rods, or 2" extensions to the damper rods. For example I have two sets of damper tubes here (definitely 1960's AMC) and neither damper tube set matches any of the spec lengths in any articles I have seen on the web, and I have looked at plenty. My hunch is that with so many variants like the Manx, P11, ES2, G15 Matchless, AJS, Norton Atlas and Commando, N15 etc etc etc it's kind of a grab bag as to what has been fitted over the years. So it would be nice but perhaps a Herculean task for someone who really knows these front ends to come up with a correct matrix to show stanchion length, damper rod length, and damper tube length by model.
The problem with the RT valves being used as rebound seems to be specific to the Norton application. I have them in Triumph forks as rebound dampers and the oil does aerate and I have been looking for the problem. There are differences in the design when applied to Triumph shuttle valve forks compared to Norton but which of them individually or collectively cure the aeration I cannot say.
1. Triumph forks seals are double lipped instead of Norton single lipped. On the bench you can feel the air compress inside the forks and the excess air slowly leaks from the threads of the fork top nut over a few minutes. On extension with no springs in play the forks try to pull back due to the reduced internal pressure until the air leaks back in through the top fork nut. Not tried this on the Norton forks but the single lipped seal maybe where the air is coming from.
2. The Triumph forks have external springs and no damper bodies so the valve is held fixed in the stanchion near the bottom and the external RT body seal is a static seal ie not sliding.
3. As the forks compress the RT valve moves downwards relative to the Fork bottom instead of being static on top of the damper body and using a sliding seal on the stanchion.
4. The RT body is custom made to provide a groove in the body for a X ring seal and the OD is a sliding fit inside the stanchion.