Raising the rear end

Discussion in 'Yamaha 250cc In-Line 4's' started by Roderz, Oct 18, 2004.

  1. Roderz

    Roderz New Member

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    Just thought I'd add a little 'How to".

    My FZR was riding a little low, and I weigh a little under 100 kgs, so that wouldn't help. So I decided to do something about it.

    One way is to get a new shock, perhaps one a little larger/longer and just adjust it to the required position.

    I've got a 3LN, but I assume the 2KR probably has the same suspension.

    It's called cantilever suspension. The shock doesn't attach directly to the swing-arm, but rather to another bracket that attaches to the frame and the swing-arm. Why they do this I don't know... maybe to save space.

    I made up some shorter risers out of a tyre iron. Make sure you don't make them out of weaker material than the originals. This brings the bottom of the shock closer to the swing-arm, which in turn raises the rear end.
     
  2. chiangstar

    chiangstar New Member

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    sounds interesting roderz... do you have any pics?

    wont raising the rear stuff around with handling?

    cheers

    simon
     
  3. Roderz

    Roderz New Member

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    I do have some pics before and after, but they don't target the change, so you may not be able to tell too easily... However, I don't put them up anywhere. If you want I can E-Mail them to you...

    Raising the rear will sharpen the rake at the front, which makes it corner much easier, although it loses some top-end stability. The fastest I've had mine up to though has been about 160km/h and I think you'd have to be doing about 200km/h to notice a difference. However, as I stated, I was lowering the back end anyway with my weight, and also I had an off on the GOR which messed with the shock a bit. The rear wheel punched up and smashed the undertray. It was never the same... So rather than find a new shock, I put it on the highest setting, and shortened the risers.
     
  4. greeny

    greeny New Member

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    i weigh about 95kg, my rear shock was on the 3rd setting. so i adjusted it to the 5th setting, much better, still a little soft, but i still have another two settings.
     
  5. blueyedjackel

    blueyedjackel New Member

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    just food for thought. i changed the dog bone links on my 3ln rear suspension for 20mm shorter ones (rising the tail) just for giggles, made the bike look stupid and felt like i was doing a full locked up heavy brakeing into a corner at 140kph except i was standing still in the garage <!-- s:roll: --><img src="{SMILIES_PATH}/icon_roll.gif" alt=":roll:" title="Rolling LoL" /><!-- s:roll: --> then i replaced then for more sensible 10mm shorter aluminium replacement ones (Definitly woudnt go any shorter) that i made cos i was curious bout how the bike would handle.
    This gave steeper (more sensitive steering) fork rake angle, less trail, slightly biasing the weight distribution forward so it'll affect things like fore aft stability and rear brakeing pressure under heavy breaking, greater ground clearance, and corner exit drive.
    i didnt like the rear being real low when i wanted to turn the rear shock preload down for a soft ride. i either had good handling, height and a hard ride (preload 6-7) or slightly less sensitive handling but low(bottoming out scrapeing pegs) soft ride (preload 2-3). now the tail sits higher and i can keep it on 3-4 but still have very good ground clearance in sharp or fast corners.
    The first thing to touch the ground on these bikes ive noticed are the foot pegs but i cant touch them down now and ive noticed my knees are slightly futher from the ground for the same lean angle. you'll also notice that when you go to put it on the side stand the bike will lean over more becos of the extra ground clearance so i just use a thick short plank in the garage to rest the side stand on now. It might fell slightly weird when you first ride round but like anything you ride round for a week or two and you wont even notice the difference anymore.

    my friend came round with his fzr 3LN1 (mines 3LN3) that he just brought and i noticed that my bike felt heavier than his when standing it upright off the side stand (both bikes were at the same lean angle). it took a few days before i finaly realised why that was.
    becos ive raised the rear ive efectivley raised the center of gravity which would make it slightly more top heavy.

    think of it like this: you have a wheel barrow half full of rocks that you're goin to dump and all the rocks are piled right up the front of the barrow(eqivalent to low C of G). Now tip the barrow up forward (lifting the bike), this will require a certain amount of force to do. The next time you have a half load again but this time all the rocks are piled down your end (high C of G) requireing much more effort to lift the barrow and dump your load. So in effect i think it would take slightly more effort or perfection of technique to flick the bike from side to side like through a slolem.

    and lastly i think there might be an ever so slighlty greater tendancy to encounter head shake (speed wobble) if you plow through a pot hole or really eneven road surface at speed on a lean eg. slightly sunken drain hole but nothing you tar scrachers need to be worried bout <!-- s:biker3: --><img src="{SMILIES_PATH}/th_Biker_3.gif" alt=":biker3:" title="Biker 3" /><!-- s:biker3: -->
    I live in Christchurch and the roads here are sadley getting crappier from the quakes which are still going off (had few 4.4's this week)
     

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