I must note with regard to the rear wheel, the 18" hub on the GPz900R
seems to be well over-engineered.
Comparing it to my ZZR1100 rear hub, they both have a five spoke
cush-drive, the 900R seems to be built much thicker and stronger,
so I would assume it could take a huge increase in power.
Whereas the ZZR600 17" wheel hub is a 3 spoke cush-drive, and although
it is more than adequate for my 'street' GPz900R conversion,
I would not try and put 200bhp through it.
I also like the fact that this engine has locknut-adjustment on tappets.
It also has good switch gear and instruments, and a good screen.
I find the GPz900R more stable at 110kph than my ZZR1100.
Maybe because it is narrower.
It has good lights.
Headlight (same as GPz400, and other GPz's etc.), Blinkers, and Tail-light,
are big and quite bright.
Put in a Philips X-treme Series Halogen 55/60W H4 bulb in the Headlight
and you double your night vision capacity.
They are bright and legal.
I tried LED tail-light bulbs, the GPz has 2 bulbs, but they are not as good
as standard 6W/21W tail-light globes.
You need a bulb that 'spreads' the light within the tail-light reflector, to
light it up correctly.
The LED bulbs I chose only focussed their light rearward, so the spread
of light was actually reduced.
The LED bulbs that do spread light are VERY expensive.
I like the fact that I can touch the ground with both feet while sitting on
the GPz900R. The seat height is good for short legs.
And the 17" rear wheel has lowered the seat by nearly an inch.
Although I may spin the rear swingarm axle-mounts 180deg to lift the
rear again - for better handling. (a 1.5"- 2" raise)
The only differences when I replaced my Keihin CVK34 carburettors for
a newly (refurbished) rack of 4x Keihin CVK34 from an A6, is that the
older version had exactly the same jetting and all settings the same except
for the main jet which is *135 on the A6 model, and it is a *100 on the A7.
I think this is part of the de-tuning the A7 suffered.
Mine now has *137 mains, and soon to be *140 as the main jets.
The carb tops are exactly the same, so no restrictions there.
Note: My replacement rack came from a USA A6 Model.
 |
| The NEW Rack of CVK34's from an A6 (USA Model). |
The airbox on the 1984 is opened on both sides of the intake - at the rear
of the airbox, whereas the 1990 A7 airbox is closed completely on the
left hand side of the airbox. I estimate this restriction to be almost a 55-60%
reduction in the airflow capacity - based on simple measurements.
This is the other part of the de-tuning of the A7 model.
I have replaced part of my airbox using the earlier model rear plate.
This is still available from your Kawasaki dealer but was ordered from Japan.
You only fit the earlier model rear plastic plate, not replace the whole airbox.
 |
| My original Airbox. I modified the rear-plate to allow increased air flow. I added the two ports on the left side. However I now have fitted the original A6 plate - seen below. |
 |
| The Original A6 model Airbox plate. |
I have a K&N high-flow 'lifetime' cotton filter (K&N KA-9084) to fit into
the original airbox - available in US and UK - not AU.
I bought mine via Amazon website. About the same cost as OEM filter.
These are washable and re-oilable, and provide a massive increase in
airflow over the standard filter.
Lifetime warranty, so never buy another filter.
I have a 40mm 4-2-1 high-flow aluminium exhaust system. (right side)
This is a Magnum original, setup for GPz900R (92DB). Better flow,
power and economy. And no Rust !
This will soon be replaced with a new stainless steel 4-1 52mm
exhaust system. (right side)
I bought this via Tony at Barracuda exhausts (see Web), because
no-one in Australia has a ready made GPz900R SS exhaust and quotes
to make one were over $2500 Aud - which in my opinion is ridiculous.
This is an absolutely beautiful system, and is made in Germany.
 |
| The Barracuda 52mm SS exhaust system to be fitted. The muffler also has a removable baffle for racing. |
The air-flow mods are the reason for the main-jet size increase.
It is an educated and measured guess without dynotuning.
And as my bike will be only for road use, I dont mind the in-exact
science of jetting based on real world road-riding, and then set the
jetting accordingly.
I will fine tune this over time, however it takes a fair bit of effort
to change jets and find the best main jet for full power.
Then adjust the needle height to match. And float height as well.
I may still get it dynoed.
See Jamie at S&R Pro at Penrith (Sydney) NSW.
I have chosen to retain the Keihin CVK34's as my preferred choice
of fuel delivery. I like the way CV carbs work.
When setup properly, they give a good balance of power and economy.
I know some people prefer flat-slide carbs for a bit extra power and
the instant throttle response they give, but if my ZZR1100 can run
160bhp from its CVK40's, then I think the GPz900R will be happy
enough with its CVK carbies.
And get NEW Carb mount Rubbers if you are replacing your
Carb Rack. It is worth it.
The original ones will be as hard as a rock, making it almost
impossible to reseat the new Rack.
When rebuilding carbies, some o-ring and other rubber seals are
quite dear to replace. Especially on a rack of 4 carbs.
I took some advice from a webite that said you can soak the o-ring
and float-bowl gaskets in acetone overnight.
They will soak some up then when left to dry they will shrink back
to original shape and thickness.
If you have any torn, cracked or worn seals you should replace them.
Make sure you get o-rings that are suited for petrol use.
I also bought braided lines for my brakes.
This is an obvious upgrade to any hydraulic brake system.
Old lines expand among other issues.
You may wish to see my http://bleedingbrakesklr250.blogspot.com
Blog about trials of bleeding brakes and a nice vacuum bleed method.
Unfortunately Australia was limited in options to have lines made,
quotes were almost 4 times the cost of a complete delivered set.
So I got them Online from Wez - at Wezmoto in the UK.
They are great however I did replace the banjos with a nicer looking
option - for cosmetic reasons only. From Venhill in UK.
Note: The UK has a lot of GPz900R's roaming around,
so parts are readily available.
I have just bought a pair of Hella twin-DB horns. They are small,
and are trumpet styled and will replace the original rusted horns.
(from Amazon US as Australia did not have these models)
I assume they will be loud but have not wired them up yet.
I do need to replace the radiator.
I will look for an increased capacity and flow aluminium model.
Nothing is made for the GPz900R that I can find.
Such it is with old bikes.
Once I find something, or get something made, I will update you.
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