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Info ZXR USD -> FZR fork conversion

Discussion in 'Tech Tips' started by ruckusman, Jul 16, 2016.

  1. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    Hi Guys,

    I'm going to be tackling this over the coming fortnight so I'll document the process

    I will be endeavouring to keep the fizzer front wheel and even perhaps the brake calipers as mine are recently enough completely rebuilt.

    First thing however is finding the correct specs for the headstem bearings
    Checking this thread - incomplete bearing dimensions

    http://2fiftycc.com/index.php?threads/my-fzr250-3ln-project.1792/

    http://2fiftycc.com/index.php?threads/my-fzr250-3ln-project.1792/quote=14451

    from this page

    http://www.dotheton.com/forum/index.php?topic=20951.0

    Cites 25 x 48 x 13 as the upper bearing dimension

    Can anyone confirm this?

    peace out

    Glenn

    2018 edit finally getting around to resuscitating the fizzer, ridiculous I know...
    head stem bearings confirmed as 25x48x13
    searched high and low for a local supplier everything on ebay originated in the UK - stumbled upon https://www.mxstore.com.au/ and asked them if they can supply 2 of the bearings I require - the response was a very prompt yes $49.95 so that's a go
     
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    Last edited: May 5, 2018
  2. Moo

    Moo Plodge Racing!!!

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    watching with interest!
     
  3. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    OK guys so a brief update to keep you interested

    research confirmed bearing sizes

    ZXR250 triple clamp will require 25x48x13 both top and bottom to go into FZR250 headstock - will advise of the required bearing seals when I've removed the Fizzer forks and triple.

    ZXR250 C -> onwards has 20mm diameter front wheel axle - wheel bearings are 20x42x12 - 6004
    FZR250 axle is 17mm, bearings are 17x42x13 - this was incorrect, FZR250 front axle is 15mm

    Now the replacement bearings to slide a ZXR axle through the FZR wheel is a 62004 which is 20x42x13 - this doesn't seem to be a common bearing size (not available on the SKF website) - the difference between the two being the extra 1mm width for the original FZR wheel bearings

    HOWEVER as I'm fitting the FZR wheel, I may be able to reuse the ZXR wheel bearings at least for the test fitting, I'll know tomorrow when I check the length of the bearings and spacer inside the wheel(s).
    Also I may not have to make up an extra spacer for the side of the ZXR axle which has the spacer /step.

    With any luck I may also be able to (re)use the ZXR's internal wheel bearing spacer.

    This could all go very smoothly

    Does anyone in Sydney have any spare fizzer front brake calipers hanging around? Just trying to get an idea of the fitup potential for the calipers without dismantling the fizzers brakes just yet
     
    Last edited: May 5, 2018
  4. Joker

    Joker CLUB250 Premium Member Contributing Member

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    ...can I ask why you're doing it? (out of curiousity). Seems like a lot of work... what are the benefits you are hoping to achieve?
     
  5. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    I've already got an R6 rear shock on the fizzer, so basically I needed something decent on the front end.

    Not as much work as is sounds, thus far all I've done is research and measure bearing sizes.

    FWIW it actually ends up being cheaper than getting new heavier springs and gold valves (even the cheap debrix ones) for my existing forks, which as it happens have enough pitting to need either replacement stanchions or new ones.

    Also the front rim that came with the forks has some (really cosmetic only) gouges which would need tidying up and then the rim repainted
     
  6. Damus

    Damus She is a BEAST and riding it is comparable to sex Dirty Wheel Club

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    I second the above and feel the venture is lunacy. After riding a good set up with conventional forks and riding a zxr with good forks I can tell you that performance wise there isnt a scrap of difference and by doing what your doing your more likely to hinder the bike. It would be a bit like changing the swing arm, a whole lot of work for a hard to determine outcome.
    I am sure there would be much higher priority components needing attention.
     
  7. Damus

    Damus She is a BEAST and riding it is comparable to sex Dirty Wheel Club

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    Thats even worse, you dont know the leverage differences of the 2 bikes and guessing suspension and getting it right is simply not going to happen. Do you even know the spring rate or stroke or anything about the original shock you replaced?
     
  8. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    @Damus Have you ridden a standard fizzer with the stock standard front forks and rear shock?
    'Nuf said
     
  9. Damus

    Damus She is a BEAST and riding it is comparable to sex Dirty Wheel Club

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    As much as what I am saying is mocking your hard work I am actually trying to point you in the right direction.
    Suspension isnt just about riding a bike and being like yep that feels wrong or right, there is a realm of other factors e.g. the purpose of the bike and what it will be doing, traction and stability under different circumstances, wheel travel, the load, ride height etc etc etc etc etc etc etc etc.
    Its not like front forks mechanically, there is linkage that changes the geometry and leverage of how effective the shock is.
    Stiffer inst ALWAYS better, you will lose stability and the smallest slip or bump could mean long term traction loss with that kind of change. I'm sorry but your guess work is poor and will lead to a horrid setup, if it was that easy id just force a cbr1000rr rear shock in my bike and put nsf250r front forks on. If your going to advertise mods you do you should at least attempt to give some reasonable logic as to how you came to the conclusions you have because it sounds crazy face.
     
  10. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

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    @Damus ....... maybe you should look back on a few of your 'crazy face' adventures into changing the course of motorcycle engineering ...... I dont put you into the catergory of 'expert' ..... in fact theres lucky to be 2 or 3 members on this forum that I would consider having the long term experience and knowledge to give out hard core advice.

    We are talking OLD bikes with 25 yr old design and engineering ...... theres areas that can be improved or an attempt at improvement at least

    FZR250s have junk suspension ..... its made at the very least for Japanese jockeys as its a JDM only bike and was never meant to be ridden by 100kg westerners.

    The R6R rear shock mod is common and anything is worth a shot with the front end.
     
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  11. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    @Damus you seriously need to do some research, I am following a really well trodden path, R6 rear shock onto FZR250's and FZR400's is well known proven effective same goes for ZXR forks onto the Fizzer as well as CBR's. I would have grafted standard R6 front forks with lighter springs to suit the bike weight had some come available easily and been suitable at a good cost. This isn't about USD versus convential forks.

    For the R6 rear shock, the weight difference isn't huge and the fizzer very often had two on the bike

    Till you can say to me definitively that you've ridden a standard Fizzer - forks and shock wise - you won't have a true understanding of it's handling issues - it really is sub par!

    Actually suspension is about something feeling right for each individual, within sensible limits of course, because everyones riding style and technique differs
     
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  12. Moo

    Moo Plodge Racing!!!

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    My old fizzer ran an R6 rear shock and different springs up front. the front end was still muck but i think that could have been changed with a revalve and maybe emulators or again a heavier spring, but it was a million times better than stock.

    @ruckusman you may have already done so, but just a suggestion with the rear shock would be to have it serviced and have the bushings replaced and then if you are looking at track time, have it set up correctly, be a suspension technician, the difference will be night and day! (im still trying to find the best and most cost effective rear shock for the ninja.

    Again looking forward in seen what the front end comes out like. best of luck.
     
  13. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    Just a correction on something

    ZXR250 C -> onwards has 20mm diameter front wheel axle - wheel bearings are 20x42x12 - 6004
    FZR250 axle is 17mm, bearings are 17x42x13 this is incorrect

    FZR250 axle is 15mm, bearings are 15x42x13 - this is correct

    I'm yet to extract the FZR wheel bearings, the ZXR wheel bearings were easily removed - remove brake discs, 65mm long x 20mm diameter Dynabolt into bearing, tighten appropriately, heat the central wheel hub for a few minutes with the heat gun, and a few hits with a hammer onto a metal bar through the axle tube and out she pops, rinse and repeat for the other side

    The FZR 15mm bearing will require a different approach as there are no 15mm dynabolts

    The FZR wheel width between bearings is longer, therefore I won't be able to reuse the ZXR bearing spacer.

    I will be able to use the ZXR axle but haven't yet calculated the amount of material to be removed off of the collar portion which goes to the RHS wheel bearing.

    A new internal bearing spacer will be easily made once I've assessed reaming the wheel centre to accommodate larger diameter tube
     
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    Last edited: May 5, 2018
  14. Damus

    Damus She is a BEAST and riding it is comparable to sex Dirty Wheel Club

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    Grey it would be nice if you could one day appreciate how far I have come in just 1 year since joining, I contribute quite allot to the forum and playing the blame game or pointing the finger without actually providing answers helps nobody.

    Ruckusman, I did do the research and am actually very knowledgeable regarding suspension regardless of bias judgement.
    To further that I know that if you used the stock R6 from a 08 model and most other years its got a spring rate of 9.8kg/mm, the fzr250 and fzr400 depending on year appear to share the same shock & linkage, I can say based on a file penske released in 08 that the racing spring rate for the fzr400 is 14.2kg/mm which is a whopping 4.4 different to yours (this is all assuming your an average weight somewhere between 70-80kg with gear on). To further that the stroke is about 10mm shorter on the r6 shock vs the original fzr shock. So without actually getting out the tape measure and doing it properly (which I highly advise) I'm willing to bet you will find that your spring is way to soft and that your going to jack up the preload to compensate for that which will in tern increase your ride height and then during heavy braking the shock will bottom out and be completely ineffective during a high speed corner.

    This can be worked out more accurately if you want to go down that road but its up to you, regarding the front forks all I am saying is it would have been allot easier to just throw the correct springs in, usd is more work then its worth.
     
  15. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    not sure of the veracity of your figures you've got, I suspect a typo(s) somewhere that's remained uncorrected

    I can't speak as to the FZR400 spring rate or suspension geometry, I don't have one to measure.
    The 400 rear shock is quite different from the 250 according to your numbers.

    However the FZR250, on the 250 original spring rate is 8.25kg/mm, therefore I've gone up by ~20% in the right direction by using the R6 shock.
    Shock travel from the specs for the 250 is 50mm, stated shock travel on the R6 shock is 62.5mm

    Are you confusing stated suspension travel at the rear wheel?

    I can tell you the R6 shock isn't softer, doesn't wallow and I haven't bottomed out, I haven't had to jack up the preload, but I did make shorter dogbones to change the steering to my liking.
    Previous tyre had scrubbed badly both sides of centre and made for ugly steering which tracked lane lines and road grooves.

    Previously it would drop into corners at slower speeds, it did 20,000Kms daily driver in traffic, all weather 7 days a week, the last 5000 Kms with the R6 shock. Changing the geometry a little steeper, to my liking ;) it has completely neutral steering and wore the front tyre evenly, I could steer the thing with just my thighs

    The two shocks differ in length by 10mm measured eyelet to eyelet
    315mm - FZR250
    305mm - R6
    That length difference is accounted for ride height wise, |FROM MEMORY| by shortening the dog bones by 8mm from 130mm centre to centre to 122mm centre to centre


    You do realise that the original FZR250 forks are really crude damper rod forks, virtually non existant rebound damping anyway, with no available adjustments of any kind, no spring preload, no compression or rebound damping adjustment and that I would have spent towards -> 1K in springs, rechromed or replaced stanchions plus gold valve cartridge emulators.
     
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  16. Damus

    Damus She is a BEAST and riding it is comparable to sex Dirty Wheel Club

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    Again that was just quickly looking and don't consider anything the internet says facts unless its measured and tested first hand.
    Ride height does not compensate for shock stroke and when I say stroke I refer to
    download.jpg
    If the R6 stroke is 60mm you shouldnt just throw that in a bike with a stroke of 50mm or 70mm just because the length compensates for the ride height/wheel travel or I wouldn't because that would mean the spring pre load would change to get it in the correct working range and the damper and rebound wouldn't be in sync with the spring as a result.
    But look again all I am saying is at least give an explanation as to how you came to the results you have, saying "others say its okay" is hear say.
    All i keep hearing is "something is better than nothing" how about "getting it right is better than something".
     
  17. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    The extra 12mm stroke is hardly a deal breaker. The issue of too much travel and rear wheel hitting something could be solved by using a thicker bump rubber and the stroke position is a minor issue. If the standard R6 spring is in the correct range, as ruckusman has suggested, then the damping, which is also adjustable, is also appropriate. Added to this the R6 shock does have adjustable damping. Unlike many owners, ruckusman has made the changes necessary to maintain the standard steering geometry.

    Ruckusman did extensive and meticulous work on the float levels of the FZR250 and reported his work on this forum. I refer to that work on one of my guides http://www.litetek.co/Guide_Mikuni_BDST_Fuel_Level.html I expect that this project will be just as thorough. It behooves us to treat others on the forum as though we were face to face as keyboard communication can easily lead to misunderstandings and bad blood. Something that is not wanted on this forum.

    Cheers
    Blair
     
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  18. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    Blair - thank you, my patience was dwindling...
     
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  19. Phil

    Phil Senior Member Premium Member Contributing Member

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    Rest assured....you weren't alone.
     
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  20. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    Just to resurrect this thread - I have actually made some progress which I'll document with pics and procedures and actual numbers in coming days.
    Digging the fizzer out of the back of the garage was a groundbreaking moment.

    Wheel conversion FZR250 -> ZXR250 axle + forks is done.
    Brake adapter plate FZR250 brakes -> to ZXR250 forks in the works - ended up being quite straight forward once I sat down with it and dealt with the issues.
    This may enable the use of other calipers - I like the look of the both the blue and gold spot R6/R1 calipers, though I have not made any measurements with them.

    One thing to mention is that I got gouged purchasing All Balls steering bearing - I won't mention the retailer, who was very good, as the issue is with the importer/distributor pricing. $50 for one bearing, when most kits of two bearings go for the same price - not impressed.

    I will say for the order time from importer -> retailer -> you - it's far better off either ordering the pair of bearings from the UK on ebay,
    or
    I am going to also ask the guy down at the local bearing store, although 25x48x13 is not a size I find amongst common tapered wheel bearings anywhere on the net.
     

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