Fork damper upgrades by JSM

Believe it or not you can make a few small "do it yourself" modifications to your stock Norton forks and get modern style compression damping and improved rebound damping.

The 1st thing to do is check for wear in the aluminum caps. New caps measure .380" ID. Get new ones or drill to 13/32" and loctite (red) in a sleeve of .375" ID .015" wall K&S brass tubing (available at hobby shops). You can get new brass caps at Decentcycles.com. Clearance must be tight or you won't have enough rebound damping.




REBOUND DAMPING:
To improve rebound damping. Place the damping cup on a socket. Tap carefully with a hammer and a tapered carpenter plumb bob to swell the open end to approx .677" (anywhere between .675" to .680").


COMPRESSION DAMPING:
If you have these type of damp tubes then its easy to cover the holes below the conical section with JS alum sleeves (or make your own) and drill only one 1/16" diameter hole in the middle of the conical section (not shown). This will give you some compression damping. The stock setup offers no compression damping whatsoever. You don't want too much or you will get a harsh ride. One 1/16" hole in each tube works out just right.



If you have damper tubes with holes in the conical section. Silver solder a couple brass plugs into the holes. Be careful not to insert the plugs so deep that they interfere with the damper rods (you should not be able to see them on the inside). Smooth them off and drill one of the plugs with a 1/16" drill bit. There must be no other exposed holes.


Use 15 to 20 wt oil.

For more info and how to eliminate fork oil leaks go to:

http://www.jsmotorsport.com/technical_Fork_upgrades.asp

Re: Fork dampner upgrades by JSM

Hi Jim

Thats a pretty easy fix to a stock set up, very interesting in fact, I have rebuilt my forks on my project bike and its been sitting for some time now till I get the time to start back on track again so I might pull them down again and do that to them, no harm in giving it a go to see how they work without spending huge mounts of money that I don't have these days, its usualy the simple things that make things work better.

Ashley

Re: Fork dampner upgrades by JSM

Isn't that the "Covenant" fix?

Re: Fork dampner upgrades by JSM

Hi Jim, these upgrades you've written up today, are meant to work in addition to your previous turkite bushing installation and damper sleeve installation instructions and parts that I followed and installed a year ago - correct? Thank you.

Re: Fork dampner upgrades by JSM

pantah_good said:

Hi Jim, these upgrades you've written up today, are meant to work in addition to your previous turkite bushing installation and damper sleeve installation instructions and parts that I followed and installed a year ago - correct? Thank you.

Click to expand...

The damper mods will work with stock bushings as well but its probably more important to get the slippery Turcite bushings in to reduce the sticktion. I worked out the rebound damping many years ago (in the race manual) before the excellent Landsdown kits became available. But only recently figured out the compression damping. The Norton factory was close but they missed it.

Someone asked me to fix the photos since photobucket has screwed me. So here is the link to a site with the photos and descriptions.

http://jsmotorsport.com/js-motorsport-technicalmore-norton-fork-upgrades/


All my tech links can be found here:
http://jsmotorsport.com/js-motorsport-technical-link-list/

Aw shucks about any thing, JBW cold weld to standard vintage alu plugs hammered in can seal damper tube less than useless lower tapper holes. In hobot case I made two rather smaller holes slightly above a lowest bigger size hole for more progressive bottom out dampening that never ever seems to hit bottom just soft indefinite stop and reversal not sensed anymore, so hunting pot hole edges and stones/curbs becomes addictive quirk trying to find Roadholder limits. Now I think about it better to put the bigger hole above two smaller staggered holes. After getting some decent sealing in the damper 'valve' expansion there more fine tuning delicousness in slightly sand paper waisting damper rod in an inch or so length at sag height with pilot on. Btw 10 mm alu rods are just enough bigger than factory steel rods to almost seal the common Alu damper cap holes so lose some mass as well as oportunity to diddle dampening to suit fork oil grade. After above mods I found all off the shelf fork fluids too harsh so explored ATF to brake fluid, compressor and hydraulic jack oil to settle on brake fluid but its moisture attraction allows spring to rust so compromised with ATF and compressor oil. I'm being snubbish on purpose in case my reports sinks in, thinner oil means faster compliance to surface imperfections w/o upseting suspension or tire grip let alone pilot comfort. Still Shame on those riding so illegally wreckless, factory Roadholders become upsetting to seek more, like me or Jimmy.

Btw Jimmy's brutal valve mode is shade tree crude compared to what Ed the tomato man has come up with using factory parts but kind of over my head at this point and he's too shy to reveal in public forums so ultimate Roadholders are yet to come for one and all. Put in ~2" longer damper rod to get full factory designed top out hydro dampening but then what ya gonna put in as spring spacer, a solid tube that nullify the extra travel and hydro stop or a weaker spring to retain stock sag or a valve spring to get more lean clearance and road shock tolerance.