Versys fork revalve

Discussion in 'Technical' started by Hoghead, Dec 23, 2011.

  1. Hoghead

    Hoghead Ol'Timer

    The Versys fork could do with some re-valving for street riding, as it is prone to hydraulic lock up over bumps and could be better tuned for both ride and performance.

    The stock springs seem fine for my 78 Kg weight (less gear) and I am going to leave them in for now and see how it copes with the re-valving, 10W oil and different oil level. I do note however, that the manual assumes a lighter rider and Racetech tells me that the stock spring is 0.78Kg/mm and I need 0.90. Changing the front springs seems a common local mod with Hyperpro being the most common brand I see. What rate are these springs as there is no data on their website other than marketing fluff about being progressive. Seemingly it is a one size fits all application.

    I think that re-valving the R leg will work, but if not it is a simple matter to buy the stock parts that Kawi saw fit not to include in the L leg and have both legs working. This will allow an even softer shim stack and/or lighter fork oil, giving better compliance over high speed inputs while maintaining control under low-speed conditions. The Versys design with the R leg doing all the work is a bit of a guess on the shim stack, and a conventional 2 cartridge design may be a bit easier.

    Having said all that, I have a pretty good idea of the shim stack that I need, but before I order what I need from the USA to do it myself, does anyone know of a suspension shop that will have both the shims, and the tools to do it right? The guys racing at Bira must have some fork specialist work done all the time.
    I have sent an email to YSS asking this question, but they have never bothered to answer me in the past and I have little hope that they will do so this time.

    Although I would like to find a competent shop with the tools, if I do end up doing it myself, I will have to buy some special tools, and the shims are in packs of 10.
    It would be nice if there are some other Versys owners who would like to give this a go to defray my costs and use up the shims. Let me know if there is any interest and I may just go ahead and get the kit to do it myself and know that it is done right

    I'm tempted to buy this software and take the guesswork and butt evaluation out of the equation. Not sure if it can handle the Versys design with one leg doing all the work
    http://shimrestackor.com/index.htm
     
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  3. Hoghead

    Hoghead Ol'Timer

    "Irish Liam" came to the Chiangmai ToyRide event yesterday and I had a chance to chat with him about the re-valve. He has the tools and experience to do the job so I am going to order the shims from the USA and give it a go. I am confident that this will solve the jolt through the bars on a sharp bump and generally improve the ride for the street.

    Shims are about 15 USD to do one the one active leg, plus Liams labour and new fork oil.
    Anyone else want to do this while I am ordering the parts?
     
  4. TonyBKK

    TonyBKK Ol'Timer

    I find the stock forks perfectly adequate for road and track.

    Most folks I know who have tried to modify them have been disappointed by the results.

    I reckon if guys can do this with STOCK suspension, that the only thing slowing me down are my lack of skill, not the bike ;)


    Best of luck!
     
  5. Ozjourno

    Ozjourno Ol'Timer

    I have to agree that the stock suspension is just about perfect for the bike and its intended use. The people I know who tinker with suspension generally love to get out the tools every weekend and play with their bikes' general set-up. If, like me, you prefer hassle free riding, go with the stock and grab a face full of wind rather than a fist full of oil. Cheers all and have a happy and safe new year.
     
  6. Hoghead

    Hoghead Ol'Timer

    The stock valving is more suited for track use than our roads, in that is is stiff and not very compliant. The response to high speed bumps is poor resulting in hydraulic lock up of the fork and the sharp jolt you feel in the bars.

    If you think about it the stock set up is a compromise. Some riders may weigh 50 Kg and ride naked, while others are 2 up, weight of 150 Kg or more total, and loaded with luggage - this alone requires different valving and springs. Add to the equation, different riding styles and road conditions and you can soon see that one size does not fit all. The Engineers had to make a compromise and that is what you have.

    Why the reluctance to change the valving, when people fit different springs with little thought to how it impacts the rest of the suspension. One needs to look at the entire package as an engineered application, and design to suit. I have the ability to do this and will do so. Others that do not fit the standard design envelope, and are experienced to know the difference should do the same.
    If you care to do a bit of research on this subject, you will find that my approach is not unfounded.

    The Versys is a great bike, however Kawi had to make some accounting driven design decisions and the one leg fork damping is one of them. The parts missing in the L leg are cheap and one can easily change to a proper 2 working leg design. This will allow an even softer shim stack and/or lighter fork oil, giving better compliance over high speed inputs while maintaining control under low-speed conditions. This is a fine point that may not be appreciated, specially if you are happy with what you now have.

    Simply doing the R leg is cheap, easy, and one can tailor the suspension to suit you. If you have never known a proper custom designed suspension, then it probably does not matter.
     
  7. TonyBKK

    TonyBKK Ol'Timer

    I never said I'm reluctant to change the valving, I just said, that in my personal opinion, it's really not necessary.

    I've ripped on some very bumpy roads with the Versys and have never experienced this "hydraulic lock-up" of which you complain.

    It does bug me that Kawasaki only allows adjustment of the right fork. I've never owned a bike with such a set-up and in my gut would feel more comfortable with matching forks sharing the load equally.

    Without seeing your suspension set up I would guess that any problems you've experienced are more likely due to improper suspension / tire pressure settings. Proper setting of pre-load, damping and tire pressure to suit your weight and the roads you typically ride should sort out your problem.

    But if you feel the need to re-valve your forks that's certainly your prerogative and I hope that it will resolve the issues you're having. Let us know how it goes. If it's not too much of a PITA I might upgrade the left fork to match the right somewhere down the road.

    Happy Trails!

    Tony
     
  8. Hoghead

    Hoghead Ol'Timer

    Changing to a more normal dual working leg fork is easy, however I am not convinced that simply duplicating the same shim stack as in the R leg, will yield the desired result. I think that if you do this then you must re-valve, but by all means try it

    You should definitely use a lighter oil with two cartridges, but how light? I doubt there is a linear relationship between viscosity and damping rate. It does appear that the difference in damping rate between a lighter oil and a heavier oil increases as suspension velocity increases---which is what we want, more digressive behavior. You might get the results you want by simply installing a 2nd cartridge and cutting your oil viscosity. Maybe something around 15.6 - 18 cSt at 40C, with a high viscosity index is not far off.
     
  9. Hoghead

    Hoghead Ol'Timer

    The re-valve is done and at the same time I changed the L leg from a pogo stick to a proper working suspension component. Cost for the parts that Kawi saw fit not to include was 2800 B retail. On a production basis it would have cost them a pittance and makes me wonder why the accountants are in charge of engineering.

    I left the springs stock for now and may change this depending on the test riding

    I used shimstacker to design a digressive compression shim stack and pretty confident that this will work fine. There is no rebound shim stack, so I am relying on the oil for rebound dampening. With 2 working legs I decided on a viscosity of 16.9 cSt as a starting point

    Preload is 25% of total range

    Foolishly I changed the rear shock at the same time so now lots of possible combinations to wade through and now the butt dyno fun begins
     
  10. jonadda

    jonadda Ol'Timer

    Im interested in revalving my forks where did you get your shims and what progression did you use?
     
  11. Joelthailand

    Joelthailand Ol'Timer

  12. Hoghead

    Hoghead Ol'Timer

    John - did not see this until now and in Mexico so do not have my notes on what shims I used

    You are about my weight so my shim stack should be a good starting point. The problem is that I am in Mexico and not home until Sept so no notes on what shim stack I used.
    If you can hang on until I get home then give me a ring
    if not shimstacker is your friend but it takes a bit of thinking to get it done

    Shims did not cost more than 15 USD and this is a universal part so you may be able to get them there. I could not be bothered with the mai mee and had them posted from the USA

    I did not see the point in using a Racetech valve when i could design a shim stack for the existing cartridge fork at a fraction of the cost
     
  13. Hoghead

    Hoghead Ol'Timer

    Back home now and speaking to David last night on valving his missing leg prompted my memory on the shim stack. David intended to simply have Nat replace the missing parts in the L leg, but as noted above this will not yield the ideal valving. If you are going to have it all apart, you may as well valve it to suit your weight

    I set mine up for a 75 - 78 Kg solo rider:
    17mm x .15mm
    16 x .15
    15 x .1
    14 x .1
    13 x .1
    12 x .1
    11 x .1
    10 x .1
    9 x .15
    8 x .3
    11 x .3
    11 x .3
    dampener rod polished, piston faces lapped and polished, back of piston radiused

    This ends up at .25mm thicker than the stock shim stack, but fits fine
     

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