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the dirt . . . on lowering forks. . . .

Discussion in 'BMX & Dirt Jumping' started by cmc, Jan 24, 2008.

  1. cmc

    cmc Turbo Monkey

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    i know that NemPro/brad/evil4bc has been doing this for a while and selling them, and that other people have done their own.

    it would be rad to see some close up pictures of the internals and what has to be modded.

    the distributor BTI, ww.bti-usa.com, sells fork tuning kits, but i don't see any of them designed to drop a dirt jumper fork from 100mm down to 80mm or 60mm. what do yall do, buy one of these kits, then cut the springs shorter. or just use the interals that are already in the fork ?
     

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  2. j.les

    j.les Monkey

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    I cut the parts to lower my Marz. DJ fork from 5" down to 3". I cut the springs down 2". Then I made 2 spacers, which were cut from an xc flat handlebar. The spacers are 2" long, to compensate for the shortened springs. I was about to put it all together when I noticed a crack in the dropouts. The fork is a 2005 I believe. I honestly don't know if this will work properly, if I get my hands on new lowers I'll find out.
     
  3. BikeSATORI

    BikeSATORI Monkey

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    ...that's pretty much all I did with mine. Got the longer negative springs/Nempro spacers, and cut a little off of the stock yellow spring with an angle grinder, then readjusted oil levels, put in some air, and was good to go.
    DJ series is simple to slam.
    I'm at 55mm with an '06 DJ2 by the way, but easily readjusted to 75 or so.

    Brad goes into his a little further than just kitting them... with polishing internals and whatnot...


    hardest part I ran into was finding a socket thin enough to grab the bolt on the bottom of the leg that holds in the cart. reg. ones won't fit it.

    sorry, no pics today, I'm surfin' on the phone lines.
     
  4. Evil4bc

    Evil4bc Turbo Monkey

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    Here's the dirt on how to home tune your older 04-06 Z-1's the Nem-Pro way.
    As BikeSatori commented you will be best off ordering the extended negative springs from us these help the most in overall ride feel and tune-ability of the fork .

    Pictured below is a 05" Z-1 cart , in this photo you can see the Titanium travel reduction shim , Extended negative spring .
    The small silver spacer in-between is the spring seat coupler , this adapt I.D. of the fork pumping rod to the O.D. of the Titanium spacer.


    Here's the basic how too on tuning and slamming you Z-1
    Tools needed
    12-mm socket ( machined/ground down so the O,D, fit's over the Marzocchi end nut)
    32-mm socket for the top caps
    Plastic mallet
    C-clip pliers
    Oil cup
    Small Philips head screwdriver
    2-mm and 3-mm Allen's
    Dermel W/ cutting disk or Die grinder with cutting disk
    EYE PROTECTION

    Steel Wool
    220 grit sand paper

    3-5 clean shop towels

    SHOK OIL Needed: 15wt or 20wt BEL-RAY or TORCO anti foaming shok fluid ( DO NOT GET 125/25cc MIX !! )

    Easy steps to fork tuning

    1. Remove the 3-mm allen bolt from the rebound adjuster if you fork has on and put the adjusting knob aside

    2.With the 12-mm socket and remove the fork end nut's
    at the same time remove the top caps with the 32-mm socket and take the upper spring out and put them aside for later , remove the upper plastic spacer and toss this away!

    3.Drain old oil into oil cup ( to be recycled properly later )

    4. Slid the lower legs off the and set these aside for later

    5. Wipe the inner stanchion tubes clean with a clean shop towel

    6. With the C-clip pliers remove the lower c-clips holding the cartridges in the fork ( I suggest doing these one at a time to avoid loosing parts , and messing up the order of assembly )

    7. After removing the cartridges you will need to unthread the small aluminum nut at the end of the cartridge assembly , if it sticks a bit clean the lower threads out there usually some excess metal shaving in there.

    8. Slide the cartridge assembly apart , making sure to lay everything out on a clean shop towel in the same order you take them apart , use the photo above for reference.

    (NOTE: it's at this point you can choose to very lightly sand the outer finish of the piston rod to remove and machine nicks that the CNC creates , then polish with the steel wool so it moves without stiction in the bottom out bumper , Go easy sanding this part is VERY THIN )

    9. After removing the original stock negative spring , you are going to RE-assemble your cartridge in the order shown above .
    Negative spring
    spring seat washer or adaptor
    Lowering spacer ( DO NOT USE PVC!! )
    Bottom out stop
    threaded end nut

    10. After reassembling your cartridge , insert it back into the forks stanchion securing it with the c-clip . Give the cartridge a little tug to make sure the c-clip has seated properly

    11. Slide the forks lower legs back on after you have re-assembled both cartridges

    12. Tighten the lower 12-mm end nut's securing the fork and the lowers together

    13. Take the yellow upper spring and put them back in the fork, you will notice there are about 6-8 coils sticking above the top cap threads.
    You will need to trim these upper coils off with the die grinder or Dremel cutting disk ( wear your eye protection ! )

    14. Now that you have trimmed the upper coils off , re grind the top of the spring coil flat

    15. Fill the fork with oil , 15-wt in the re-bound side , 20-wt in the non adjustable side , you want to fill the fork up until the oil is about 1" to 1.50in from the top cap threads with the fork compressed
    Remember when filling the fork you have to cycle the fork up and down to remove any air trapped in the cartridge assembly , do this slowly or the fork will spit oil up at you , not fun!

    16. Once the fork has been cycled and the oil is filled to the proper height , insert the spring cut side down .
    there should still be about 1/2 a coil above the top cap threads this is good it will add a small amount of pre load to the fork , don't go crazy and make the spring too tall or your fork will feel like a pogo stick and top out very harshly making that pop/clunk noise

    17. Tighten the top caps back down and check the fork out making sure everything is working OK and all the nuts have been tightened and that the rebound is adjusting properly and your off to the races as they say!

    Good luck hope this helps everyone
    -Brad
     
  5. Boxxer

    Boxxer Monkey

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    I took mine to a grinding wheel and it worked well on Zokes until I used, or rather tried to use it to take off the front caliper on my R1. Lets just say it lost and Yamaha uses gorillas to tighten bolts....

    Side note, or primary note: I do have an 08 Fox 36 float on the way which will get slammed. I asked fox what they thought, they said it sounds like a good idea :)
     
  6. Castle

    Castle Turbo Monkey

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    Boxxer, don't quote me on this, but if I understand the float series right and they haven't changed much as far as travel adjustment in them. I don't see any reason you couldn't add a extra spacer to take it to 70mm. I'm guessing that's what fox confirmed was ok.....?
     
  7. FrontRangeDH

    FrontRangeDH Monkey

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    Boxxer, I slammed mine yesterday, super easy and quick to do. Took me 45 minutes to do 2 Floats
     
  8. cmc

    cmc Turbo Monkey

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    thanks brad !
     
  9. Evil4bc

    Evil4bc Turbo Monkey

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    Your Welcome , glad I could help!
     
  10. FreeRide-Junkie

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    Killer write up Brad.
     
  11. allsk8sno

    allsk8sno Turbo Monkey

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    ok i am about to do this to my 03 DJ1 and afew Q's come to mind,

    first, why cut the spring?? my fork has the black spacer i could just trim, using the trim as the spacer perhaps?? (assuming correct diameter for the cartridge)

    and second what is the benefit of the longer negative spring? is the stock topout spring horrible?? seems like your slowing the rebound enough to limit harsh topout
     
  12. Evil4bc

    Evil4bc Turbo Monkey

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    1. When lowered to 65mm the coil-spring will be longer then than the fork so you have to cut a few coils out , the black plastic spacer is crap throw it out if you use this for the lowering spacer it WILL break and you will have to do the entire job over again along with picking small pieces of black plastic out of your dampers .
    This happened to Santiago Garicia right in front of my Interbike booth one year , hi fork when from 65mm to 165mm in one bunnyhop Classic!

    2.Longer negative sping stops that harsh CLUNK that the fork makes when you pull up hard for a jump , it also helps the fork track the small bumps in the terrain. The stock negative spring is only 3/4" in tall , when you run increased air pressure this spring car easily be compressed and thus rendered useless . so a much higher spring rate is required along with more spring stack to help the fork compensate for the increased forces from street and DJ riding .

    good luck
    -Brad