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650ss Roadholder

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650ss Roadholder oil damper

Posted by stefan_koop at July 11. 2018

Good evening,

i found these oil damper tubes with 4 holes under the cone in my 1967 650ss roadholder forks.

New oil dampers (from norton motors) have on hole in the middle of the cone.

I saw a modification with one hole above the cone.

 

What is the result respectively the difference comparing these type of tubes ?

 

Stefan

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Re: 650ss Roadholder

Posted by paul_standeven at July 12. 2018

New damper tubes have the oil holes immediately above the tapered section.  This gives a better performance by achieving a progressive hydraulic lock at full compression of the fork.  You can read about the Covenant damper conversion here:

https://www.rgmnorton.co.uk/csi/1245184/f/pdf/050007_covenant_fork_damper_improvement_kit.pdf

The kit includes a top bush extension piece to give a progressive hydraulic lock at full extension as well.  It's available from RGM for £12

If you want to improve your fork performance, it's best to start with making sure your fork has good stanchions, bushes etc.  The top bush on the damper tubes wears with time, so make sure this is a close running fit.  The Commando got a compression damper plate (it's at the very end of the damper rod, immediately under the nut at the end) with shallow flats, instead of the milled slot as on the earlier forks.  This gives much more compression damping.  It's a useful improvement and costs £5 each, Andover Norton part-no: 03.0584

Re: 650ss Roadholder

Posted by stefan_koop at July 12. 2018

Paul,

thank you for your comprehesive comment.

do this dampers come with the bush extension? https://www.rgmnorton.co.uk/buy/alloy-fork-damper-body-cap-with-bolts-improved-damping-short-r-holder_2281.htm

And it seems that the oil hole is on th eright place (above the tapered section) ?

 

 

 

Stefan

 

 

 

Re: 650ss Roadholder

Posted by paul_standeven at July 12. 2018

Current RGM damper tubes have the holes drilled in the right place.  I have two sets of unused nos RGM damper tubes of the old type, bought for a project bike.... on of them an alloy Norvil set.  The bush extension is part of this set of parts:

https://www.rgmnorton.co.uk/buy/covenant-fork-damper-conversion-kit-improves-damping_2294.htm

If you have new damper tubes, you will not need the alloy dowels which are supplied to block the cross-drillings in the original=spec damper tubes.  The bush extensions are 1.5" long, to give the progressive hydraulic lock at full extension.  If you have a set of well-worn bronze upper bushes, they may be cut to 1.5" and fitted to do this job at no expense

As a further aside, an engineer friend of mine says that the upper bushes on Norton forks are too short, and advises making longer ones, ideally of teflon.  So if one were to make a set of teflon bushes, as standard but 1.5" longer......

Paul

Re: 650ss Roadholder

Posted by Bob Matthews at July 12. 2018

Previously paul_standeven wrote:

As a further aside, an engineer friend of mine says that the upper bushes on Norton forks are too short, and advises making longer ones, ideally of teflon.  So if one were to make a set of teflon bushes, as standard but 1.5" longer......

Paul

Like these from RGM - except theirs are in brass or bronze.

I wonder though with the longer top bushes, does it increase the stiction of the fork action?

Re: 650ss Roadholder

Posted by paul_standeven at Saturday 00:31

Yes, this RGM bronze bush is the length of a standard bush plus 1.5", so gives the same result as the Covenant conversion but with lower loading on the bush because it is long.  Various people prefer teflon or turcite, a relative of Delrin.

Paul

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