Fork dampening question

stockie2 · Dec 24, 2011

Merry Christmas to all,

Packed the kid's presents and just have a few minutes to ask a question after rebuilding my forks today.
I have the covenant setup installed and Norbsa's bronze dampened caps. I also machined up some damper pistons in bronze, the original steels were quite loose in the damper tubes.

I spent a bit of machining time making up new fork top bushes out of bronze, I made them 30mm longer than standard, to try and get a hydraulic lock on top out, rather than the damper rod hamering.

I fitted the dampers less the spring to test the compression and rebound characteristic's.

Rebound feels really grunty with 10 weight oil, but and I understand compression should be about half of rebound, but compression feels pretty weak. Do I have to pack the damper pistons to get stiffer compression, or what is the trick to adjust?

Cheers Richard

john robert bould · Dec 24, 2011

Norton fork dampers are not designed for compression resistance, but adding more oil could increase
the pnumatic action ,some maxton conversions use "air space" to give this effect.

Hobot · Dec 24, 2011

Go ask Norbsa for the rest of his fork kit to get the silent top out if you can even hit something to cause that afterwards. Most the rebound dampening in Roadholders is d/t the fluid passing gap in rod and damper cap, with Fuath's kit the damper rod is tighter fit than factory and you can slightly neck down a short section where most the road annoyance texture motion occurs leaving the rest full size for progressive dampening action I like better than high end forks I've ridden on and off road on. The other feature of Greg's kit is the extra spring involved that doesn't come into play till nearing the stops so hardly can hit or jump anything that tests the silent soft indefinite stops reversals. Beware to over fill as air space pumps down and can hydrolock after being fooled for 1/4 mile woowheew poopoo. About 175 ml is about tops. In my Fuath type forks I found power steering fluid was best. Once ya get the sliding action controlled - it may temp ya into more flings on power which then reveals then need of stiffening/raising the fork harmonics by a fork brace.

stockie2 · Dec 24, 2011

Thanks all & Ludwig. So the round washer with the truncated (squares cut off) lets fluid through for compression dampening. I was wondering if the amount of end-float between the squared of washer and the damper piston had a bearing on the given compression dampening result. Maybe I should just try the forks now, after the new dampener caps and new pistons I have never noticed so much rebound before, and there is slight compression there, so maybe with the springs added it will be tolerable?

Cheers richard :roll:

norbsa48503 · Dec 27, 2011

Maybe I should just try the forks now, after the new dampener caps and new pistons I have never noticed so much rebound before, and there is slight compression there, so maybe with the springs added it will be tolerable?

Yes just drive it. You might play with the oil type to tune it in to best for you. Most come back to me saying it is as good as their new bike's front end. The make up springs went up in price again so I will have to adjust the price of the kit again.

Hobot · Dec 27, 2011

In the olden days some put a little spring between the damper washer and a drilled or slotted back up washer so its closed up fluid flow on compression and opened to fluid flow on extension. Greg do ya know anyone that's played with necking down your fatter damper rods and cap fit for low dampening in the couple inches of road texture motion but left the rest a tight fit for progressive dampening in both directions?

I've not felt a modern with as good feel as your simple kit in Roadholders much to my great surprise and secure pleasure. Ford must think there's a growing cult restoring their old tractors.

stockie2 · Dec 27, 2011

Thanks Hobot & Greg,

I will give her a try today if the Sydney weather plays ball, will report back. I also played with some bushing of the front axle, I was somehow 1/4 under natural fork width of 5 1/4" between bottom eyes. I figure I may have been increasing the stiction through bind up. The original complaint was the bike was bobbing, or nodding at the front on smooth surfaces. I have balanced the wheel etc.
I trawled through the net, and found an article on using race tech gold valves, but then a foot note that fitting two will takeaway your compression dampening, and the other option is to fit just one and run the system similar to Landsdowne, one comp damp, one rebound! On a brighter note, I then found that the Mikexs site where we get the breather valves from has the same type of gold valves, that suit XS650's for very reasonable money. They fit early Showa 35's the same as on my other ride a mid 70's HD Shovel. So there's another project, although the old Harley rides pretty good with decent Progressive shocks in rear, the front end was not so bad, but the shim stack tech of soft on fast acting bumps, and stiff on slow should be good to sample one day.
Also there is a story that certain model CBR600 internals will fit, but that's another tangent, If I can keep it simple with what I now have, I will be happy, maybe?

Cheers Richard :roll:

john robert bould · Dec 27, 2011

stockie2 said:
Thanks Hobot & Greg,

I will give her a try today if the Sydney weather plays ball, will report back. I also played with some bushing of the front axle, I was somehow 1/4 under natural fork width of 5 1/4" between bottom eyes. I figure I may have been increasing the stiction through bind up. The original complaint was the bike was bobbing, or nodding at the front on smooth surfaces. I have balanced the wheel etc.
I trawled through the net, and found an article on using race tech gold valves, but then a foot note that fitting two will takeaway your compression dampening, and the other option is to fit just one and run the system similar to Landsdowne, one comp damp, one rebound! On a brighter note, I then found that the Mikexs site where we get the breather valves from has the same type of gold valves, that suit XS650's for very reasonable money. They fit early Showa 35's the same as on my other ride a mid 70's HD Shovel. So there's another project, although the old Harley rides pretty good with decent Progressive shocks in rear, the front end was not so bad, but the shim stack tech of soft on fast acting bumps, and stiff on slow should be good to sample one day.
Also there is a story that certain model CBR600 internals will fit, but that's another tangent, If I can keep it simple with what I now have, I will be happy, maybe?

Cheers Richard :roll:

I have had a bit of a run on Aussie damper orders this year, last ten sets heading down-under. You may meet up with someone sporting a set :!:

www.lansdowne-engineering.com

ashman · Dec 27, 2011

Hi

I brought a set of John dampers, they have only been on the bike for just over a week now, man what a big improvement from the orginal dampers, my 850 is in a Wideline Featherbed frame, I put new seals in and the new dampers,a new front Avon tyre, I throught the Featherbed handle very good but now its even better, I'm going through corners a lot harder and the frontend is so much smoother, I got the dampers adjusted about 3/4 of turn out from fully closed and I think it's just right for my Norton, just got to adjust my rear Koni shocks now to to work with the front end, I have been running my Koni's on the meduim spring setting so will adjust them to the soft setting but my Koni dampers are set on 5 as I push my bike hard in corners.

So spend some money and get a set of Lansdownes dampers, I'm glad I did, thanks John.

Ashley

stockie2 · Dec 27, 2011

John/Ashley,

Yes I would like a set of LD's but Christmas severley limits bike funds, I am just mucking around in the shed with the lathe for now, so cost are negligable so far.

Cheers Richard

john robert bould · Dec 28, 2011

ashman said:
Hi

I brought a set of John dampers, they have only been on the bike for just over a week now, man what a big improvement from the orginal dampers, my 850 is in a Wideline Featherbed frame, I put new seals in and the new dampers,a new front Avon tyre, I throught the Featherbed handle very good but now its even better, I'm going through corners a lot harder and the frontend is so much smoother, I got the dampers adjusted about 3/4 of turn out from fully closed and I think it's just right for my Norton, just got to adjust my rear Koni shocks now to to work with the front end, I have been running my Koni's on the meduim spring setting so will adjust them to the soft setting but my Koni dampers are set on 5 as I push my bike hard in corners.

So spend some money and get a set of Lansdownes dampers, I'm glad I did, thanks John.

Ashley

Ash,
Thanks for the feed back, Happy New year.

Brooking 850 · Dec 28, 2011

John did you end up sending my set to New Zealnd??
I am home on the 5th Jan hopefully the elves have delivered and maybe installed them???
Regards Mike

Fork dampening question

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