GPZ900R Antidive issue

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

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.

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

Here is the pictures










Thanks
Lucas

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.

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

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.

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.

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.

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.