GPZ900R Antidive issue

[Ninja89]

Hi guys,

I have an issue with my GPZ900r 89, The anti-dives are leaking again. I took it into a bike shop previously and they told me they rebuilt it and gave me a 30 day warranty. Its not 8 months later and the bastards are leaking again. I looked for a kit online i could try and do it myself and i only found forums where people directed those looking for a kit to the gpz zone website. when i went there i could not find any kits just a few other things. Not sure what i am looking at really but i thought the kits use a fair few o-rings and such and i couldn't find that anywhere on gpz zone and i cant find anyone else that sells them.

In my findings i also found people talking about Bypass plates. I purchased a set from Demonspeedracing.com and they have arrived......Just curious if others have used bypass plates and what their thoughts where on them? Also if anyone has a guide on how to go about installing them. It seems like a unbolt and bolt on gig but if I've learned anything about my bike in the last 4 years ive had her she's a bitch to fix when stuff does go wrong. But i just love her to bits and cant see myself without her!

Thanks for any help!
Lucas

[Gosling1]

the o-rings used in the rebuild 8 months ago, were probably not resistant to brake fluid. You need better o-rings - this will stop the leak. All that goes wrong with the anti-dive units is the return spring on the control valve fails, or the o-rings fail. When set up properly, these units work well. I don't have a GPz900R, but do have an '84 ZX1100A3 (GPz1100) - the anti-dive units on this bike are pretty similiar to the 900R and work exactly as the manufacturer intended .

Block-off plates can work but they must be machined properly, to allow fork oil to flow through the holes - otherwise the front end will get real solid real quick Don't ever just bolt on some flat plates.

[Ninja89]

Hi Gosling

Thanks for the info. I had a look in the pack I received for the bypass plates and it seems to have a cavity to allow fork oil. Should I take a picture and post it to be sure?

Thanks
Lucas

[Ninja89]

Here is the pictures










Thanks
Lucas

[Gosling1]

Lucas - if you can re-size those pics, that would make it easier to see the block-off plates properly. I guess as these are specifically-designed for the 900R, they should work just fine. Personally, I love the feel of the anti-dive units on my 1100 - they work well on that bike.

[Ninja89]

Hey gosling.

Thanks for your message. I decided to take the plunge and just do it. In doing so i noticed the fork oil that dripped out of the antidives when i took them off is a smoke Gray. Is that normal?

Thanks
Lucas

[Gosling1]

yeh that is a normal colour for fork oil that has been in use for some time. Its not that colour when new, but changes colour pretty quickly in use.

[Shifty]

Unless you are insistent on maintaining originality, you should look at a fork conversion.

They have quite commonly been converted with front ends like ZZR600, ZX6, etc. Depending on what you choose you may only need a few spacers machined, other options might need more involved things such as custom triples.

The rear end is also fairly easily converted and then you've opened up a myriad of options for good tyres.

[Gosling1]

Custom triple clamps cost a squillion bucks. By far the cheapest and most effective way to adapt a different front end to any bike - is just replace the centre stem on the bottom clamp that you want to use (i.e. - the clamp from the donor bike, say a ZX6 or ZX9R, whatever) - with the centre-stem from the original triple clamps.

I have done over 1/2 a dozen front-end swaps on different bikes over a few years now - the local machinist who does my conversions has also done a lot of other local conversions as well. He can either turn up a completely new centre-stem and press that into the donor front-end lower clamp, or modify the donor front-end centre stem to suit the dimensions of the existing frame ( in this case, the GPz900R frame).

Total cost for any conversion I have done, has never exceeded $250. Custom triple clamps on the other hand - can run into the thousands. Its a complete waste of money unless you are looking for the visual effect of a massive set of billet alloy clamps up the front - which some people are looking for and are happy to spend the money to get......

For a GPz900R, my advice would be to look for a complete front end from a ZRX1100 or 1200. These retain the standard look, have really meaty staunchions and you can get some good bling for the brakes ( radial conversions, wavy discs etc).

Rear end conversions can be a lot trickier - depending on the swingarm/shock combo used, there is a bit of work in modifying or fabricating linkages, upper shock mounts may need modding etc etc - chains often have to be offset to allow for wider rubber......by comparison, a complete front end can just be bolted up easily once the centre stem is modded.

[Shifty]

All good advice. As I mentioned some are simple and some can be very involved

Custom triple clamps cost a squillion bucks. By far the cheapest and most effective way to adapt a different front end to any bike - is just replace the centre stem on the bottom clamp that you want to use (i.e. - the clamp from the donor bike, say a ZX6 or ZX9R, whatever) - with the centre-stem from the original triple clamps.

I have done over 1/2 a dozen front-end swaps on different bikes over a few years now - the local machinist who does my conversions has also done a lot of other local conversions as well. He can either turn up a completely new centre-stem and press that into the donor front-end lower clamp, or modify the donor front-end centre stem to suit the dimensions of the existing frame ( in this case, the GPz900R frame).

Total cost for any conversion I have done, has never exceeded $250. Custom triple clamps on the other hand - can run into the thousands. Its a complete waste of money unless you are looking for the visual effect of a massive set of billet alloy clamps up the front - which some people are looking for and are happy to spend the money to get......

For a GPz900R, my advice would be to look for a complete front end from a ZRX1100 or 1200. These retain the standard look, have really meaty staunchions and you can get some good bling for the brakes ( radial conversions, wavy discs etc).

Rear end conversions can be a lot trickier - depending on the swingarm/shock combo used, there is a bit of work in modifying or fabricating linkages, upper shock mounts may need modding etc etc - chains often have to be offset to allow for wider rubber......by comparison, a complete front end can just be bolted up easily once the centre stem is modded.