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Thread: Need help showa forks bottom out k-tech

  1. #1
    Evil Twin mad biff's Avatar
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    Need help showa forks bottom out k-tech

    hi guys im having trouble with my mille front forks ,very easy to get them to bottom out
    can even get them to give heavy knock if i forget ,the forks have been done by k-tech i dont know when as i just got the bike 8 months ago .i never
    noticed it at first but not long after when i got to know the bike and started having real fun it started doing this ,there are no leaks from them all looks very good ,and i have set to standard settings was bit better .the bike has stood for 2 years before i got it there is a zip tie on the fork for a marker its allways on the bottom i have never done fork repairs before so i aint got a clue ,cant understand why its like this as the bike handles very good ie:muirkirk road on race mode its perfect .
    can anyone help with info or is there someone who knows what there doing and can come sort it for me for a fee i dont like bike shops as they tell you anything just to rip you off i just need it sorted its driving me mad.. cheers guys

  2. #2
    Baby Twin
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    If the forks have been worked on by K-tech, I think there could be 3 options as to what they did, a revalve, a 20mm cartrige kit or a 25mm cartridge kit. The last two are less likely as they are 400 upwards and are in reality track only. The forks will be sprung to a given rider weight and they provide a data sheet showing spring rate, oil type and grade, air gap and suggested settings.

    The likelihood is that you'll need fresh oil as a minimum and new springs depending on the weight they were built for.

    If you know the name of whoever had the work carried out you might be able to get the necessary info from K-tech to do this work independently. If you don't, by far the best solution is to send them back to K-tech, they will know what's been done when they look inside and they can sort them out to your requirements (probably cost 120-150, but check that).

    I've had 5 sets of race bike forks modified and the 2 sets that K-tech did were better than anybody else's efforts (inc Maxton). It's a bit of a shame you are so far from Leicester where K-tech are based, although they may well have a reliable Scottish agent.

    The cheap, but risky option is to add 20mm of fairly heavy oil to each fork and wind up the compression damping a bit to see what happens.

  3. #3
    Retired
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    As said your forks probably need more oil. The damping curve in the last third is greatly affected by the air gap in the forks. (you can compress springs and air but not fluid). if the previous owner was a light rider he would have needed less oil otherwise his weight transfer would never overcome the rising rate of the fork compression to get proper travel. if your heavier you are breezing through the travel before the compression rate ramps up enough to stop you. Setting the sag will tell you if the spring rate is wrong. if you can't get less than about 40mm of sag with you on in gear without loads and loads of preload then the spring is too soft. My money would be on the oil though.

  4. #4
    Evil Twin mad biff's Avatar
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    hi and thanks for rep/ ive not tried adding oil but have messed with all settings which made allmost no change bit better on the standard ones
    but after looking at some posts i guess it must be needing a flush and new oil .i do have a read-out from k-tech .
    make =showa
    reads spring =rate 9:-0 n
    compression =1 turn out
    rebound = 1 3/4 turns out
    sag without rider =25/30 mm
    top yolk = standard
    oil level air gap =100 mm
    oil viscosity = 5 wt .

    20-piston-reb
    20-piston-comp
    20-valve-spring loadsof shimms and sh%t 203 + vat

    lol just seen date when done 3/2/04 omg 7 years ago i did say the bike stood for a while .bike was mint like new could have been track bike ? i dont know ..i have all the old parts from forks also i might rebuild with them im 12 stone so standard springs should be fine but i will try new oil first see how it goes ..thanks graveltrap and spoonz
    Last edited by mad biff; April 19th, 2011 at 01:42 PM.

  5. #5
    AMA Pit Boss redratbike's Avatar
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    I'd email K-tech and ask their advice first

  6. #6
    One Liter Duc Eater apriliamoto's Avatar
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    Mad Biff, this bike sounds familiar, what year is it mate?

    EDIT: Ignore what I said mate, Ive just seen the pics in ya profile
    Last edited by apriliamoto; April 20th, 2011 at 12:02 AM.

  7. #7
    Baby Twin
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    I'd email K-tech and ask their advice first
    This is a good plan, they will probably have made a set up for something like Motul 5 weight oil, so it will be bloody rubbish if you fill it with Silkoline 10 weight.

    Also the Showa forks get very fussy once the air gap drops much below 100mm. The only K-tech data sheet I can find for similar forlks is for my RS250 proddy racer (very similar forks), but K-tech use a 100mm air gap in those, so that's probably a starting point.

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