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GPX250R Suspension Question

Discussion in 'Modifications and Projects' started by Milpool, Mar 5, 2016.

  1. I'd love to do something with the suspension on my GPX250R; it's pretty common knowledge it's way too soft on these and not adjustable.

    I'm mostly interested in just doing the rear for now because that looks like something I could actually do myself, but if I'm making the back stiffer and leaving the front stock is this going to be bad/dangerous for handling? I will be doing the front sometime down the line but right now I don't feel mechanically confident enough to do it myself.

    Also would this: KAWASAKI NINJA 250R EX250J REAR SHOCK GOOD COND bolt straight in? And is it adjustable?

  2. GPX250 Suspension Enhancement

    how much sag do you have with the current shock?
    if too stiff, the rear can top out after going over bumps. but the later adjustable ones can be adjusted softerer

    front is actually pretty easy if anything like the ZZR250.
    just need to get a slightly longer tube (between spring and top cap) to increase preload, and maybe put slightly thicker oil in.
    need some way to hold front of bike up while forks are off, and may as well do seals while you are there.
    if seals are ok, it really doesn't take long to install a longer spacer
    Where can I get some preload spacers? - Ninja250Wiki
    they reckon it's not good, but it worked well for me. I went from 100mm to 111mm spacer, and now my sag is good, and doesn't dive.
    adding a little more oil in fork will increase the air spring effect, but may decrease travel, gotta be careful with that sort of change.

    if the rear is higher but front still sags, then it decreases the fork rake (angle), maybe make it a bit more twitchy, and will still dive under brakes.
    may do weird things in corners, since front will compress more than rear.
  3. Idealy with the bike off all stands and you use your foot to push down on a peg standing next to it, it should move similarly on both ends. Thats a rough and ready test for balance.