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GPX250 Suspension Enhancement

Discussion in 'Modifications and Projects' started by Samboss260, Sep 24, 2012.

  1. Given that the very soft and spongy suspension on the GPX, I've decided to address this, so that it can aid in my cornering techniquw and learnings.

    So this is the plan...

    - Replace the current rear shock, with one from a post-2008 Ninja 250R, as they are firmer and adjustable. Found several on ebay in the US, and after using "findapart.com.au" (great website and tool) I found and ordered a second hand shock off a 2009 Ninja that only had 2,420 kms on it.

    - Replace front springs with some from Sonic Suspension. I've found the part, with a spring rate of 0.70 and will be ordering it shortly.

    - When the front springs get fitted, I will have the fork oil changed also.

    Hopefully this will firm up the spongy front and rear ends, stabilise the bike in the corners a bit more and stop or minimise that diving under brakes, which I just hate.

    So keep posted, to see how this mini project comes along....
  2. I used to have a GPX250.

    It was not unlike a rocking horse.

    Good luck, and don't over-capitalise :)
  3. Parts will be around $370, and labour I'm not sure of. But from I've been told, it isn't a hardvorvtime consuming job to do.

    And if it changes the handling of the bike for the better, then it will serve my 8 months left on my RE's well.
  4. You shouldn't need to pay labour for the rear shock. It's literally just two bolts to remove and a second person (or car jack) to lift the rear wheel slightly to line up the new one properly. 15-20 minutes at most, though I'm sure a mechanic would charge for at least an hour.

    Front springs are a little more involved but still nothing to be scared of. It's no more complicated than changing the fork oil, which is something all bikes need done on a regular basis anyway (so it's a useful thing to learn). Should only take 4 hours at most - less than 1.5-2 if you know what you're doing.

    The money spent is definitely worth it, especially when you consider how much money people waste on aftermarket mufflers for 250s which achieve basically nothing (other than drawing attention from the cops and requiring a considerable effort to suitably re-jet the carbs).
  5. Sounds like a good weekend project ....

    Cheers JD.
  6. They are the right things to do and even though I haven't bothered as I'm not keeping mine much longer, they all make good sense.
  7. Money spent on good tyres, suspension and brakes is always money well spent. 1000 times better than bling and noise.

    Edit. The next best thing to spend your money on, is putting petrol in the tank, to ride that bike thousands and thousands of kms in all types of weather and on all kinds of roads:) My 2 cents anyway
  8. Do GPX run USD forks?
  9. A cheaper shock upgrade is the SV650 shock. If you are hanging onto it for a bit longer the emulators are worth their weight in gold.
  10. It's also massively oversprung for anything but the fattest riders, raises the rear of the bike by 2.5 inches, and requires grinding away parts of the bike to get it to fit.
  11. Well, installed the rear shock tonight, and what a difference.

    Before we started, I took a level and set it across the seat and measured down to the ground, with no weight 920mm and with me on it 880mm.

    New shock installed, on the least firm setting and same level setup for measuring, no weight 924mm and with me on it 890mm. So a sprung net difference of 6mm and it feels a lot firmer.

    Took it up another notch, and no weight height is the same at 924mm but with me note bike it was 910mm. And it feels nice and firm.

    I'll take it out on the weekend for a ride to see the difference.