81 GPZ1100 Road Racer

After a couple of years without a old Kwaka race bike, I am toying with idea to build one up.
Have spent a bit of time trawling through this forum and the net to get some ideas.
I have a 81 GPZ1100 frame and most of the motor in the shed and thought I would utilise it.
As it would be log booked for Period 5 (bikes from 1st Jan 1973 to 31 Dec 1982) racing in Australia, there are a few rules I need to follow to be eligible.
So at this stage, I am looking at a ZRX swingarm as I can run up to a 5" rim. Hopefully they will allow it, otherwise I will have to go with something more period friendly.
We are allowed 41mm forks, so I was thinking that a ZR750 front end would be good. It was mentioned that it is a straight swap. Does anyone know anymore about it?
There are a couple things I am not too sure on, and I was hoping someone might be able to help or point me in the right direction.
Firstly is frame bracing. Anyone know where is best on these frames or if there is anyone in Australia to see about it?
Secondly is brakes. They need to be from the period or replicate those manufactured in the period. Does anyone know what the best from that time frame is, that are relatively easy to source?
Any info or advice is welcome.
Once I get everything figured out and parts sourced, I will do a build thread as well. Thanks.

What State are you in ? I found this pic on the web with a small description of its mods for period 5.

"KAWASAKI GPZ100/Z1100 P5 RACE BIKE:37mm CR carbs, ZXR swing arm, brembo brakes, Manta disc's-forks-brace-triple trees-, CBR 600 legs, Scitsu tacho charger, wets and wheels , spare Ohlin's shocks, Dyna Ignition, Dyna coils , Dyna leads, Moriwaki cams-spring-retainers, Moriwaki 11.5:1 pistons, light crank, modified oil system cooler"


Try contacting someone like Rex Wolfenden from T REX racing developments in Victoria, if he doesn't know it, it doesn't exist....
T-Rex racing developments 03 9457 5411

750 R1 wrote: What State are you in ? ]

I am in SA.
Thanks for the info. I think I have seen that bike before at a race meet somewhere.
I did have a KZ750 a few years ago that had the ZXR swingarm swap, but it limited the tyre size and tyre warmers were always hard to get on and off due the the tight fit. It worked well though. I had 39mm Yamaha forks and discs (FZ), the forks were solid but the brakes left a bit to be desired.
Might give Rex a call, I have picked his brain before. Might head to the SA classic state title in January to get some ideas as well.

There would be a better option than the ZR7 forks , you are going to have to add springs and emulators to make them up to standard anyway. Didn't FZR1000's in the late 80's have 41mm forks ? They may have more adjustment, ZR7 have no adjustment as far as I know ?. The track is the right place to get idea's...

Yeah, I was not sure about the ZR7 forks, as I know little about them. I just remember seeing someone online (maybe here) say they are a easy direct swap. Plus there was a ZR7 getting wrecked nearby the other day.
My original idea was to use 90-97 ZX6 forks which are 41mm. Might go back to that plan.

What ever you use, just make sure that they are long enough, I think they need to be around 790mm to 800mm, That's the length I'm using on my 1982 GPZ750R1, which is the little brother to your bike basically.. Included in this length is the fact that the GPZ handlebars mount o top of the fork legs, take that into consideration ...

check out this thread on frame bracing.
kzrider.com/forum/5-chassis/294594-frame-bracing?limitstart=0

"laying down" the shocks will help give you a more progressive shock

over-sizing the engine bolts for a tight fit helps.

Over-sizing the swing-arm pivot to remove the generous factory slop goes a long way.

check out the AP Lockheed calipers. they make replicas of the caliper that Eddie Lawson and period racers used. They are not the cheapest and can be hard to come by. Or check out the Brembo P108 caliper. functionally it is a copy of the original Lockeheed calipers. They are still produced by Brembo and very reasonably priced.

DoctoRot wrote: check out this thread on frame bracing.
kzrider.com/forum/5-chassis/294594-frame-bracing?limitstart=0

"laying down" the shocks will help give you a more progressive shock

over-sizing the engine bolts for a tight fit helps.

Over-sizing the swing-arm pivot to remove the generous factory slop goes a long way.

check out the AP Lockheed calipers. they make replicas of the caliper that Eddie Lawson and period racers used. They are not the cheapest and can be hard to come by. Or check out the Brembo P108 caliper. functionally it is a copy of the original Lockeheed calipers. They are still produced by Brembo and very reasonably priced.

Sandy Kosman has had some CP2696 copies made up at a very reasonable price

slayer61 wrote: Sandy Kosman has had some CP2696 copies made up at a very reasonable price

Do you have any current sources? The only thing I can find is that Kosman sold the business in 2010, and the URL for kosman specialties is dead.

For the Brembo P108, has anyone tried to use these with a 78-80 KZ1000 aluminum cast wheel? I'm curious if the back of the caliper fits between the rotor and wheel spokes without contact.

laying down" the shocks will help give you a more progressive shock

Is the change in rate from the typical laydown actually significant? I went through the process of working out the math a few years ago, and I came up with a very minimal change in rate. But it turned out to be pretty complicated to do buy hand, so it's very possible I messed it up. And I can't find my notes now.

From the VFT "Products by racers, for racers" or something like that

Sandy Kosman SK Racing Products 707-799-7639 sandykosman@gmail.com

I just emailed him last month about widening wheels & he said he is "old & retired".

slayer61 wrote:

laying down" the shocks will help give you a more progressive shock

Is the change in rate from the typical laydown actually significant? I went through the process of working out the math a few years ago, and I came up with a very minimal change in rate. But it turned out to be pretty complicated to do buy hand, so it's very possible I messed it up. And I can't find my notes now.

Yoshimura was the first one to do this on his GS1000 race bikes, Moriwaki did the same thing, it has an obvious effect of more travel to the rear wheel, therefore more adjustability, you need a slightly heavier spring to compensate for the bigger angle {or lesser, depending on how you look at it}. The Yoshi and Moriwaki bikes layed the shocks over at 35.5 degrees, I used to have a PDF of the full Yoshi set up but my computer crashed and I've been unable to find it since....

750 R1 wrote: The Yoshi and Moriwaki bikes layed the shocks over at 35.5 degrees, I used to have a PDF of the full Yoshi set up but ...

I'd love to see that. I'd really like to understand the intent and goal of the mod.