To recap, the forks on my 1956 Dommi 99, at full extension, leave a gap of about an inch and a half from the bottom of the lower fork shroud to the top of the chrome seal retainer. I determined the stanchions were wrong ("long" Roadholder rather than "short.) Found a set of proper length stanchions, but they didn't fix the problem. Reason: a previous owner (probably looking for more suspension travel) fitted both longer stanchions *and* longer damper tubes in the lower fork legs (9-1/8 inch Commando style rather than 7-34-inch Dominator style.) The damper tubes come dear; Norvil currently lists them at £48 each, plus shipping (I'm in the U.S.A.). Anybody know of any other sources?
Also, the previous owner went hole hog and fitted later damper rods. Is there any difference between them other than the top threads? Dominators use cycle thread; Commandos use UNF. If there's no other difference (length, valve size), could I get away with using the existing rods with the correct damper tubes when I find some? Or is that penny-wise and pound foolish? (Norton only want £9.60 per rod, but I'd have to add top nuts of correct thread, £8.60 each)
I have handled this proble…
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Availing myself of the ser…
Availing myself of the services of a machine shop did occur to me. Any idea of the thread pitch? I've seen info that says the Commando damper tube top thread is 28tpi ... ?
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Possibly an outrageous che…
Possibly an outrageous cheap fix.
Would it be possible to fit some form of spacer inside the top of the damper between the damper piston and the top cap. If is was around4 cm long it would push the slider up by roughly this amount and solve the gap problem. Some thick-walled Aluminium tubing perhaps. Or how about a heavy duty spring? This would help to stop the clang when the forks extend after riding over a large bump.
The only down side to this would be the preloading of the mainfork springs.
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Previously jim_algar wrote…
Previously jim_algar wrote:
Availing myself of the services of a machine shop did occur to me. Any idea of the thread pitch? I've seen info that says the Commando damper tube top thread is 28tpi ... ?
Hi Jim,
I know that this is perhaps an old chesnut but I have the same problem as you experienced - over extending forks when on the centre stand.
As yout forks were OK before you restored, the stansions and internal were all OK before so did you ever find the source of the problem - tried following the forum but could not find the conclusion - and did it all turn out OK?
Best regards
David
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I have handled this problem before when only commando parts were available. Disassemble the damper tubes, shorten them by the appropriate amount, rethread and reassemble them. This requires someone with a lathe and some minor ability. The damper rods should be the same length and need no change. Also, if you want hardchromed fork tubes, the Commando tubes can be shortened the same way, but do it at the bottom. It is easier to remachine the bottom of the tubes as there is no threading or taper required. The lathe will be needed here as well.