GPZ750 fork questions

[leep]

Hi All

I have a 1984 gpz750 with the anti dive units on the fork lower legs, one side has started to leak from the weep hole at the top of the anti dive unit, its not on the brake plunger side of the unit as that weep hole is dry and when separated and brakes pumped remains dry, the oil if definitely fork oil. in reading the service info from back in the day it mentions that they are not serviceable....has anyone experienced such leaks and been able to rekit/repair such a leak????

I know a lot of people got rid of the anti dive unit arrangement all together, however I want to keep this bike original.

on another issue, I replaced the fork oil a while ago but was surprised how little oil the manual referenced for each fork leg, my bike is the zx750 -a2 UK gpz model and the service info references 248.5 cc of oil per leg, with a final fork oil level of 185mm with forks compressed. does this sound right???? it seems like bugger all oil and the forks feel quite springy when the front of the bike is pumped up and down manually instead of feeling more compression resistance which I would expect. I'm not sure if this how they are meant to be??? my previous bikes had upside down forks and felt completely different

cheers

[Gosling1]

those specs for fork oil capacity and measurement are correct for the ZX750A model. The previous model 750's used more oil in the forks, around 300ml per leg.

In the factory manual for this bike, the very first note under the heading 'Anti-dive System' says that the assembly cannot be repaired or individual parts replaced - you need to replace the entire system.

But - the manual also says that if the leak in the a/d assembly is fork oil, then either replace the assembly or the o-rings. There are 2 small o-rings between the a/d assembly and the fork legs - maybe these are all that need to be replaced ?

There is also a test for the brake-plunger assembly - do you have this test in your manual ? I can copy it and post it up here if you need.

[leep]

Gday Gosling

cheers for your help once again mate, I have the manual and see how they mention that the anti dive unit cant be repaired, As I'm a nosy bugger I have stripped the top plunger out of the dive unit as its only held together with a circlip, as far as I can see, it may be bypassing the upper plunger body oring and then out the weep hole, for the sake of a 50c oring i will replace and refit and see how it goes....failing that I'm reluctantly off to the wreckers

I thought I had the oil capacity correct but it just doesn't seem like much, is it normal for these front ends to be quite easy to compress the forks by pushing up and down on the bars??
It just doesn't feel like much compression resistance when I push down compared to other bikes Ive had

cheers

[Gosling1]

I think with the description you have given - bunging in a new O-ring in the a/d unit may well fix this one. I guess by 'weep-hole' you mean the bleed nipple ?

Good luck with a search at the wreckers, I think you should also put a request through Findapart.

Your fork springs are probably sacked out, this is why the front end can be pushed up and down easily, it's not really a function of the fork oil - having said that, you can always experiment with a bit more oil if you want to, maybe an extra 10ml each leg at first....but my guess is that if the fork springs are OEM ones - then they are >25 years old, and stuffed. A good set of Hagon springs from Darryl at Moose Racing in Euroa, or even a set of Progressive Suspension springs from Ikon in Albury will fix this problem. Expect to pay around $150-ish for a pair of good fork springs - best thing you can do for the front-end really ...

[leep]

Cheers Gosling

no the "weep holes" im referring to are actually cast holes, i guess they may be referred to as tell tale holes aswell, the brake plunger side of the unit has one at its rear(fork leg side) and so does the A/D unit, must be for a visual indication of internal failure past the orings.

I'll check out the after market springs too

thanks for all your help

[Gosling1]

no worries, hope this problem can be fixed with just a couple of o-rings, that would be great

[Lurch]

Ive got the same prob with the RHS fork on Goose.
Looks like I'll be doing the same. Thanks for the info dave

[Gosling1]

no worries mate, hope you get ole' Goose up and running soon !

[Lurch]

well, on the way to teh rego inspection the small weep let go, and turned into a full-on leak.
Needless to say - failed one inspection.
Luckily Thumper bought my old forks over - now just waiting for craig with a big enough allen key for the lower triple clamp.

[leep]

Well Im pleased to report $1.50 for two orings and reassembled.....all is like new again. got to love that!!!

[Gosling1]

Cool ! any fix for $1.50 ya gotta be happy with that ....

I had a bit of a closer look at the a/d units on the RX forks last weekend - and spotted the 'weep' holes you mentioned......tiny little bastards aren't they ! - will be interesting to see how these a/d units work once Grandpa ReX is up and running......

[leep]

tiny little pains in the ass that's for sure Gos, but all is sweet now for a bargain basement price
cheers