1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Pinned Fitting Chinese FZR250 3LN Fork Preload Adjusters 34mm x 1.5mm pitch

Discussion in 'Yamaha 250cc In-Line 4's' started by my67xr, Feb 10, 2018.

  1. my67xr

    my67xr Well-Known Member Premium Member Contributing Member

    Messages:
    2,393
    Likes Received:
    1,494
    Trophy Points:
    698
    Joined:
    Jun 18, 2016
    Gender:
    Male
    Occupation:
    Panel Beater, Spray Painter, Custom Fabricator
    Location:
    Adelaide
    My Bike:
    Yamaha's, FZR250 3LN3 1990, XT250TS 57R 1986, IT200L 43G 1984
    So i've now fitted my aftermarket Fork Preload adjuster's to my FZR250 3LN3
    These replace the standard fork top bolt's/cap's and give's you 17mm of spring preload adjustment, plus they earn you a few point's in the bling area :thumb_ups:


    The FZR250 fork's use a soft fork spring in them as standard,
    this is most likely due to the average weight of the 17 year old Japanese rider, Height 170.80 cm (5' 7"), Weight 62.60 kg (138.0 lb) ?

    By the time you compress the spring and fit the forks' top cap on you have added preload to the spring, then when you get on the bike you are adding more preload.
    I have read that most sport's bike's have around 50mm to 55mm preload with the rider

    Adding preload adjuster's to your fork's can raise the front of the bike a bit so that with the rider on it you can adjust it to suit the weight of the rider.
    The suspension will still be sitting in the area of 50mm or so preload, but with the preload adjuster's it can be easily adjusted to suit the rider's weight and or the road condition's.
    Usually for the suspension to be comfortable you need to give the fork's about 30%-35% sag with the rider sitting on the bike so the suspension is not fully extended nor is it fully compressed.
    I don't think i'll need to adjust them much for my weight (66kg's) but i'll let you know how i go when i try them out.



    These are the Preload Adjuster's i bought for my 3LN3 off of Ebay, they have a 34mm tread with a 1.5mm pitch.
    The preload adjuster in the rear of the picture was one of the wrong one's that were sent first. (seller sorted the issue for me quickly though)
    Make sure you confirm with the seller before buying them to check you are getting the correct one's for your bike (thread size and pitch)
    This is the seller i used- https://www.ebay.com.au/usr/aaamotorhk?_trksid=p2047675.l2559

    20180209_172153.jpg




    Tool's required to do the job
    A 1/2" drive ratchet, a deep 22mm 6 point socket, a decent 6mm allen key, a 2.5mm allen key, and an old 5 litre oil container and a clean rag

    20180210_150224.jpg
    20180210_152246.jpg



    Start off by putting the clean rag on your front fender, now slide the oil container on top of the rag/fender and push it up under your windscreen fairing
    This help's to keep the fork's extended and makes it easier to put back together

    20180210_152517.jpg



    Now you can undo the 6mm Allen head bolt's that hold's your fork in the top tripple clamp, and the other 6mm Allen head bolt that clamp's you bar's to the fork leg
    Next undo the top fork cap (22mm) with your 22mm deep 6 point socket and ratchet, and remove it from the fork tube
    I found that doing them one at a time is easier

    20180210_152031.jpg

    20180210_152601.jpg



    Now with the fork cap off you need to remove the winged adjuster from the new preload adjuster so you can fit the socket on to the head of it, use the 2.5mm Allen Key
    And use some silicon oil/grease on the o'ring so it goes back together easier and doesn't get damaged

    20180210_152827.jpg




    Fit the new preload adjuster onto the fork spring spacer and use the deep socket to push it down then start the thread and do it up by hand
    (this require's a little bit of downward pressure to get the thread to start inside the fork tube)
    Tighten the new fork adjuster nut up so it's firm in the fork tube, then do up the 2x 6mm allen key's to hold the fork's in the tripple clamp and bar's to the fork's

    20180210_152926.jpg

    20180210_153144.jpg



    Now you can move onto the other side
    My FZR250 is the 3LN3 so it has a remote brake reservoir, this need's to be undone and swung to one side to allow you to get in and undo the Allen head bolt's and top fork cap on the right hand side.
    Remove the old fork cap and replace it with the new preload adjuster (use silicon oil/grease on the o'ring to help it go in easier) and do it up firm, then do up the 2x 6mm Allen Head bolt's

    20180210_153647.jpg


    Now all you need to do is remove the oil container and rag, then fit the adjuster knob's to the new fork cap's and do them up with the 2.5mm allen key
    And refit the brake reservoir (for 3LN3 and newer) to the post and do up the bolt.

    20180210_154452.jpg



    So that's it, time to pack up your tool's and get your bike out and adjust the Preload Adjuster's to suit, then off for a ride
    Total time taken was around 20 minute's, minus taking the pic's etc


    20180210_154524.jpg 20180210_154514.jpg
     

    Attached Files:

    • Nice Work Nice Work x 3
    • Like Like x 2
    • Winner Winner x 2
    • Thanks! Thanks! x 1
    Last edited: Feb 10, 2018
  2. my67xr

    my67xr Well-Known Member Premium Member Contributing Member

    Messages:
    2,393
    Likes Received:
    1,494
    Trophy Points:
    698
    Joined:
    Jun 18, 2016
    Gender:
    Male
    Occupation:
    Panel Beater, Spray Painter, Custom Fabricator
    Location:
    Adelaide
    My Bike:
    Yamaha's, FZR250 3LN3 1990, XT250TS 57R 1986, IT200L 43G 1984
    So today i took the FZR out for a ride to see how it feel's
    After bouncing the front a bit after each full turn, and trying to feel where it was nice i stopped at 4 full turn's.
    Took the bike out and within about 1 km i had to turn the adjuster's back 1 turn as it was a bit firm.
    Went another 2km's and it still felt a bit firm so i backed it off another full turn.
    Left it at 2 full turn's down for the rest of the 80km ride and i'm pretty happy with it there for the moment.
    The pitch of the adjuster bolt's is 1.25mm (M8 bolt), so at 2 turn's down it has added 2.5mm of preload to the spring
    I'll take it out again through some windy hill's road's next and see if it need's any more adjustment.
    It's a lot easier adjusting it than trying/swapping spacer shim's each time
     
    • Like Like x 4
    • Informative Informative x 1
  3. minimac

    minimac Member Premium Member Contributing Member

    Messages:
    17
    Likes Received:
    10
    Trophy Points:
    13
    Joined:
    Dec 31, 2017
    Gender:
    Male
    Occupation:
    retired nuclear nomad
    Location:
    Oswego, Ny
    Nice write up and how-to. Do you think using a lighter weight oil might allow better adjustment to get what you want?
     
  4. my67xr

    my67xr Well-Known Member Premium Member Contributing Member

    Messages:
    2,393
    Likes Received:
    1,494
    Trophy Points:
    698
    Joined:
    Jun 18, 2016
    Gender:
    Male
    Occupation:
    Panel Beater, Spray Painter, Custom Fabricator
    Location:
    Adelaide
    My Bike:
    Yamaha's, FZR250 3LN3 1990, XT250TS 57R 1986, IT200L 43G 1984
    The front end is pretty soft on the FZR's,
    so when i changed out my fork oil a couple of month's ago i used heavier weight oil, 15w over 10w.
     
  5. Wozza

    Wozza Active Member Premium Member Contributing Member

    Messages:
    223
    Likes Received:
    129
    Trophy Points:
    148
    Joined:
    Mar 21, 2017
    Gender:
    Male
    Location:
    South Australia
    My Bike:
    GB250
    Have you done a sag test?
    my butt is so old it has no idea on what feels right, so I tend to go with sag testing..to me it always feels way to hard but have to admit the bike feels more planted on crap roads....

    just reread you OP, you said 30 to 35 % sag, its supposed to be 30mm to 35mm sag front and about 20 to 25mm rear typo?
    https://www.motorcyclenews.com/new-.../november/feb23-05-how-to-set-suspension-sag/
     
    • Like Like x 1
  6. my67xr

    my67xr Well-Known Member Premium Member Contributing Member

    Messages:
    2,393
    Likes Received:
    1,494
    Trophy Points:
    698
    Joined:
    Jun 18, 2016
    Gender:
    Male
    Occupation:
    Panel Beater, Spray Painter, Custom Fabricator
    Location:
    Adelaide
    My Bike:
    Yamaha's, FZR250 3LN3 1990, XT250TS 57R 1986, IT200L 43G 1984
    Yeah, they have 30mm sag with me on the bike i checked this morning

    The page i looked at yesterday is http://www.promecha.com.au/sag_preload.htm

    It say's 30% - 35% sag, which work's out roughly to be 35.1mm - 40.9mm as the FZR250R have 117mm of front travel
    So i'm not too far off atm, i might back the adjuster's off another half a turn and try it out again.
     
    • Informative Informative x 1
  7. my67xr

    my67xr Well-Known Member Premium Member Contributing Member

    Messages:
    2,393
    Likes Received:
    1,494
    Trophy Points:
    698
    Joined:
    Jun 18, 2016
    Gender:
    Male
    Occupation:
    Panel Beater, Spray Painter, Custom Fabricator
    Location:
    Adelaide
    My Bike:
    Yamaha's, FZR250 3LN3 1990, XT250TS 57R 1986, IT200L 43G 1984
    I've dropped back the preload adjuster's to 1.5 turn's out and been out riding a few time's now, front sag is 35mm.
    They are a touch softer and the fork's bottomed out tonight when i hit a big pothole coming back through the hill's but the rest of the time it feel's pretty smooth.
    Front brake's are feeling good still too.
     
    • Like Like x 3
  8. GreyImport

    GreyImport Administrator Staff Member The Big Cheese Contributing Member

    Messages:
    7,208
    Likes Received:
    4,332
    Trophy Points:
    943
    Joined:
    Jun 14, 2012
    Gender:
    Male
    Occupation:
    Troublemaker
    Location:
    North by NW NSW Oztralia - Tamworth
    My Bike:
    *Kawasaki ZXR250C *Yamaha FZR250R 3LN1 *Suzuki GSX250 *Triumph Bonneville 750 T140V
    @my67xr

    This is a cap off my spare 3LN1 forks ... looks to be the same thread as yours ... ?

    Im going to get a set of adjusters from old mate for my street bike and Project X ... but Ill message him beforehand

    stock fork tops (Medium).png
     
  9. my67xr

    my67xr Well-Known Member Premium Member Contributing Member

    Messages:
    2,393
    Likes Received:
    1,494
    Trophy Points:
    698
    Joined:
    Jun 18, 2016
    Gender:
    Male
    Occupation:
    Panel Beater, Spray Painter, Custom Fabricator
    Location:
    Adelaide
    My Bike:
    Yamaha's, FZR250 3LN3 1990, XT250TS 57R 1986, IT200L 43G 1984
    • Like Like x 1
    • Agree Agree x 1

Share This Page