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GPX250 bouncing under hard braking

Posted: Sun Jan 14, 2007 10:59 pm
by MiG
I've got a 2003 GPX that's done only 11,000 km. Judging by the service interval table, the fork oil and suspension should be fairly fresh.
However, under hard braking the front end bounces quite a lot. It's not headshake, just up and down bouncing.

Is this normal for GPXs (I've heard the suspension is pretty basic) or do you think something is wrong? I'm a fan of hard braking (both in my crappy Verada and my bicycle) so I'm finding it pretty annoying that I can't brake to the tyre's full potential.

BTW, I only weigh 76 kg so it's not like I'm squashing the bike.

Posted: Sun Jan 14, 2007 11:09 pm
by RG
I had the same problem with my ZZR, apparently they are normal.

I had 1/2" spacers put in mine to harden it a little.

Re: GPX250 bouncing under hard braking

Posted: Sun Jan 14, 2007 11:16 pm
by Ratmick
MiG wrote:Is this normal for GPXs (I've heard the suspension is pretty basic) or do you think something is wrong? I'm a fan of hard braking (both in my crappy Verada and my bicycle) so I'm finding it pretty annoying that I can't brake to the tyre's full potential.
The suspension on the old GPX is pretty basic, but seems to work ok. Is your front disk ok?

I had a 2000 GPX250R and the only thing that would happen under really hard braking is that the bike would dive at the front. It didn't 'bounce' as such unless you let go at the brake at maximum dive and re-grabbed max brake again after the suspension had rebounded.

You can pull them apart and stiffen them a bit if it's causing angst. Have a look here, these guys are guns: http://faq.ninja250.org/wiki/Suspension

HTH.

Re: GPX250 bouncing under hard braking

Posted: Mon Jan 15, 2007 12:03 am
by Johnnie5
MiG wrote:I've got a 2003 GPX that's done only 11,000 km. Judging by the service interval table, the fork oil and suspension should be fairly fresh.
However, under hard braking the front end bounces quite a lot. It's not headshake, just up and down bouncing.

Is this normal for GPXs (I've heard the suspension is pretty basic) or do you think something is wrong? I'm a fan of hard braking (both in my crappy Verada and my bicycle) so I'm finding it pretty annoying that I can't brake to the tyre's full potential.

BTW, I only weigh 76 kg so it's not like I'm squashing the bike.
well actually you are prob about 26kg above the design parameters
dont expect that at 11k the suspension has had fresh oil

usually pogo is a sign of not enough rebound dampening

a replacing of the fork oil with some spacers would be a good start

Posted: Mon Jan 15, 2007 7:12 am
by FrogZ
Id say bingo on the "they have never been touched" scenario.
You can just about be the original fish (minke whale?? :lol: ) oil has turned to water and th springs are sagged to buggery.
I be the brake fluid is just black crap too by now.
These are the two things no one ever seems to change/check no matter what has been done to the bike or the service schedule says. :wink:

Posted: Mon Jan 15, 2007 11:35 pm
by MiG
What I meant was that the schedule says the fork oil only needs replacing at 24,000 kms, so it shouldn't be too crappy yet. Although it also says every two years. I'm not being too logical about it then. I think I'm trying to avoid changing it :)

Brake disc seems fine. There's no pulsation of the lever and just a slight change in the rubbing noise as you roll the bike along.

Do you guys recommend going for one grade thicker fork oil, or just replace it first and see how things go?

Posted: Mon Jan 15, 2007 11:47 pm
by Johnnie5
fork oil lasts 10K if you are lucky

change it now , go with a quality oil and see how it goes

fork oil is cheap anyway

keep your 20c pieces , you might be needing them to set some more preload