Z500 for racing

Hi,
I´m thinking about using an early Z500 for Classic racing.

Has anone here some experience from doing that?

I think what i need to do first is fitting an oilpan from newer 550 that has outlets for oilcooler and fit oilcooler, Change to steel braided brake lines and good pads and maybe harder front springs.

Welcome to the forum sixten.
Here in the states we never had a Z500. We are going to have limited experience with racing one. There are a few racers here, but we dealt with the KZ/GPz line of bikes. I did some racing on a 500, but it was a Yamaha. Not sure that's gonna be any help. I can tell you I didn't run a cooler on it, if that helps at all.

And Welcome again.

The Z500 is almost same as the 550, only with a 3mm smaller bore. Tons of guys raced those bikes so there should be lots of info available. Corey Clough is a member here with lots of experiencing racing 550's. You might want to look him up and pick his brain.

Huh, multiple oil pan questions today. Here are some things to look for in 550 oil pans.
s3.amazonaws.com/gpzweb/OilPans/Kz550oilPans.html

Yes it is the same bike as KZ550 I understand.

I bought a bike and fitted some old fairings, big oil cooler, 4-1 exhaust, foam air filters, steel braided lines and new pads.

I shortened the front springs and put a long spacer to compress the spring more and welded one of the holes in the “damper” to get more damping.
But the forks are still not very good

Maybe it’s possible to use forks from another bike? Preferably one with 18” wheel as 19” racing tires are limited.
It has to be parts that was available 1980 because of the regulations for classic racing in Sweden.

The only racing tires I found are Avon AM18, F2 and AM26.
Has anyone here got any experience from those?

hi sexten, nice bike, good to see another racer from europe.
i raced for many years in the italian championship 500 class, but with a Honda CB500/4, never had a z500 in the class even if they were sold in italy
Later i raced also a Gpz550 but it was in a bigger class due to cc
did you put an oil cooler at the end?
can you explain what is the problem with the fork? in theory you did the right thing by shortenng the springs and adding spacers, the question is what is the spring rate AFTER the change. in any case the post 1984 gpz550A model fork is much better, maybe try to find one

Hi,

Did the CB500/4 race in the same class as a Z500 would?

Yes i put a big oil cooler behind the front fairing.
it was to big to sit in the original place.

I didn’t measure the spring rate after I cut it but it still feels week.
I will try it on track and add pressure to the forks until it’s stiff enough.
also the “damping” it not very good still but I bought very thick oil and will try that.

is 84 GPZ the same diameter? 36mm

I have now tried it on track and the forks are very bad.
Also I cant find a 19” front tyre that will survive racing in hot conditions.
So I want to swap the front forks for something bigger and with a 18” front wheel. 

any advice on possible swaps?
It has to be parts available in 1980 or similar tech.

wrote:

I have now tried it on track and the forks are very bad.
Also I cant find a 19” front tyre that will survive racing in hot conditions.
So I want to swap the front forks for something bigger and with a 18” front wheel. 

any advice on possible swaps?
It has to be parts available in 1980 or similar tech.

 
The first model Z1R Kawasaki {1978} ran an 18 inch front wheel, so did the KZ1000 police bikes from 1978 onwards, I think they were 2.15 inch wide, The Z1300 also ran an 18 inch front wheel but is disc spacing is very wide so I wouldn't use one of those...

The manual lists the 1984 Zx550A1 (Gpz550) as having an 18" front wheel.  Most likely the 1985 Zx550A2 (Gpz550) would as well.
The forks on those models had anti-dive features, but I think Corey Clough figured out it was easier and better to just convert to stiffer springs and block off the anti-dive system for racing.

wrote:

The manual lists the 1984 Zx550A1 (Gpz550) as having an 18" front wheel.  Most likely the 1985 Zx550A2 (Gpz550) would as well.
The forks on those models had anti-dive features, but I think Corey Clough figured out it was easier and better to just convert to stiffer springs and block off the anti-dive system for racing.
 

I also found out similar. I have an 83 gpz550 with the air assist. Having ridden some more modern bikes with damper rod forks properly set up (racetech cartridges) I wanted something cheaper but good.

I blocked off air assist by removing all the over the fork tube paraphernalia, then I threaded the air holes for a tiny flat and shallow grub screw. Then used some marine epoxy to really seal the hole shut.

Then I did YSS fork cartridges (or race tech if you have $$$ for them) and drilled out the damper rods as per the instructions and installed them.

The forks are a lot better. I set them stiffer than I should have (my bike is considerably lighter than the factory bike and I'm not as heavy as I expected myself to be by about 50 lbs now thanks to diet and some modest exercise) but they work great.