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Progressive fork springs

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Al
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#46 PostAuthor: Al » Wed Aug 10, 2016 11:09 am

A year on, thought it was time for an update.
Been at Odiham, Oulton Park, Spa and Cadwell and there have been some changes albeit slight but due to some incidents, unforseen circumstances and natural developments, some adjustments have had to be made.

Bearing in mind that these settings are for track use i am posting to highlight the subtleties in changes, to give an indication of how much difference, small adjustments make with this set-up.

The original set-up, once it was initially in a place that was suitable.

Rear rider (full) sag 12.5 mm
Front rider (full) sag 37.5 mm
Fork main spring pre-load 5mm (equal to the minimum recommended)
Emulator valve springs Yellow (64 Lbs / inch)
Emulator valve spring pre-load 3.5 turns.
Fork oil 20W (True S.A.E.)
Oil level is 135mm bottomed with springs out and emulators in.
16 mm of fork top leg protruding through the top yolk.
Front tyre pressure 29 PSI
Rear tyre pressure 35 P.S.I.
Tyres Conti Attack CR2
Weight at front wheel 105 KG
Weight at rear wheel 106 KG.

Settings now. Changes highlighted in red.

Rear rider (full) sag 12.5 mm
Main linear springs Bike sag is 26mm Front
Rider sag (full) for both bike and rider) 37.5mm
Fork main spring pre-load = 11mm, achieved with several plain washers above the plastic tubes.
Emulator valve spring pre-load (Yellow 64 Lbs) 4 turns from just open.
Oil weight 15W (true SAE) I'm likely about to change back to 20W
Oil level 120mm from top of tube, compressed fully, springs out, emulators in.
20mm of fork leg sticking out above top yolk.
Air pressure = zero when bike on wheels.
Front fork full travel under full brake was 3 1/4 inches


Everything else not highlighted in red stays the same. You could say that those items which are highlighted are the ones that make the most difference or that they are the ones that will never be right to satisfy different criteria. Eg. different tracks or differing conditions.

Dont think i posted the part numbers for the bits i have fitted either;

Valves; FEGV S 3501
Linear springs; FRSP S 2938 (0.95 Kg/mm)

These are in standard J forks / standard J yolks.
Emulators would likely be the same number but spring rate would differ depending on various things like bike and rider weight / intended use etc. etc.
I could see a possible problem with 1100 B forks / yolks / bars in that i think the bars hold the upper legs to a given fixed height. I think that may end up with the front end riding too high but not sure if that can be got round somehow with maybe a tubular spacer outside the stauntion.

Anyone been playing with these on a road set-up??

AL
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#47 PostAuthor: Fred the Zed » Wed Aug 10, 2016 7:53 pm

Great info Al.

Mods and changes mapped out brilliantly. Will the same part nos fit other Zeds... Z1R for example? I need to sort the seals on my 78 Z1R so I might as well change the springs and oil and try the emulators out.

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#48 PostAuthor: Al » Wed Aug 10, 2016 8:57 pm

How ya doing Fred?
No not those numbers for the Z1R. They divide the series down into sets and yours would be included in the Street, Kawasaki, KZ1000, 1977 to 1980 collection.
Not being patronising but those are the selections you need to make from this page

http://www.racetech.com/VehicleSearch

http://www.racetech.com/VehicleSearch#g ... ar=1977-80

Think it said 36mm forks for the 1R, where the J ones are 38mm.
It looks as if the Shed may need some "Fork Emulator Adaptors" AD 3003 P.
But i would really speak to them to confirm this first.

If youre sure about what you want then fine but they list spring rates for about six or seven different needs!

Mine are 50% stiffer than standard from 0.65 Kg/mm to 0.95 Kg / mm.

Shout out if i can help. When i opened the spring box the last thing i expected to see was a bit of thick walled plastic tube!!!!!!!!!!!!!!:shock:

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#49 PostAuthor: Fred the Zed » Sat Aug 13, 2016 1:18 pm

Cheers Al!
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#50 PostAuthor: Fred the Zed » Mon Oct 31, 2016 10:56 am

Time for an update on Zorded's great thread...

I've eventually got around to ordering the bits and pieces from PDQ for my 78 Z1R..

As I'm a hefty bear at 16st odd:

0.85kg Springs: FRSPS 2341085

Adaptors for Z1R: FEV AD3003P

Emulators: FEGV S3001

All in, including postage was a total of £296.05. (But prices about to go up)

3 week wait for the parts from the US. :roll:

Race Tech reckon 15w oil.

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#51 PostAuthor: Z1parR » Mon Oct 31, 2016 10:51 pm

Nice one Rich :up
Thanks for sharing your findings and experience .
0172 . Geoff Parr

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#52 PostAuthor: Fred the Zed » Tue Nov 01, 2016 9:50 am

Z1parR wrote:Nice one Rich :up
Thanks for sharing your findings and experience .


Its what makes the Z1OC world go around. :D
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Re: Progressive fork springs

#53 PostAuthor: Coose » Fri Jun 09, 2017 6:56 pm

Following up from All's post above, we've been in conversation over the last few weeks (months maybe?) about forks and stuff, where I assumed mine were stock and ok with a little air, but air in forks is not right as it's too inconsistent.

So, last week I ordered some 0.9kg/mm Racetech springs, and found out that YSS make a direct copy of the Racetech emulators but for £67 from Wemoto! You can find them slightly cheaper elsewhere, but Wemoto keep them in stock and were kind enough to quickly confirm the dimensions.

So today I threw it all together, using Al's settings as a benchmark: -

Preload: 15mm (I can shorten the tube if necessary).
Oil: 15w Silkolene, 120mm gap (emulators in).
Emulator setting: 4 turns out of 7. There is only one spring with the YSS valves and I'm unsure of the rate.
Damper rod: 6no. 8.5mm holes drilled.
Fork springs: 0.9kg/mm.

I tried to measure the sag but it was a little hit-and-miss due to new bushes, but it seems to be around 30mm static and about 45mm laden. So, a bit more than Al's as expected, but more on this later in the test-run report...
I'll get a few more miles on it and will measure again.

Now the important bit. I started riding through town towards one of my usual test routes and immediately noticed the difference. The roads around here are shocking, but now I have high-speed damping control and barely noticed the bumps!

Riding out of town I overtook a car and it properly shook its head as I crossed the crown in the road. So, I wound up the steering damper, which masked the problem beautifully.
So, down one of my favourite wiggly bits and it felt great, though still nervous. I stopped and let a little air out of the front tyre to make it less pointy and straight away I could back off the steering damper a little, though it was still lively.

I then headed for my local test track, which is awesome but the surface is terrible - it looks like a farmer had dragged a plough over it!
What I did find was that I could just pin it and I didn't notice the horrible surface, so a massive improvement! I stopped to contemplate, dropped a bit more air out of the front, which solved the problem and I could then back the steering damper to where it was.

I got home, let the tyres cool and found I still had 34psi in the front! I then dropped this to 32 and I'll see how it goes. I'm not sure how much was originally in there, but I must have been drunk when I pumped it up... :wink:
Though, on standard forks it felt better with a higher front tyre pressure.

So, a massive improvement for not a great deal of money. It's always going to be a compromise, it doesn't handle like an R1 but it never will and I don't want it to! :)


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