2. A Brief History of the GPz900R

1984:

Most of below is taken from a few selected Web pages - with gratitude.
I have added my opinion, and some updates about my specific bike.

The original bike was released in 1984.
It was groundbreaking in many engineeering respects, and a showstopping bike in
looks and performance.
And, according to sources, the first of its kind, for a production bike for many
technological reasons.
It is considered by many people to be the grandfather of the modern sportsbike.

Firstly, it uses an inline-four configuration which is Watercooled.
It has a 4-valve head.
It has Double Overhead CAMs, and a side mounted CAM chain which reduces the
width of the engine.
This type of engine configuration seems to be settled on as the 'norm' for many
modern sportsbikes today.
And is used in race bikes like the MotoGP, 600's, and Superbikes.

Secondly, It uses the engine as a 'stressed' member in the frame.
It was found that the lower downtubes, using this particular 'spinal' frame design,
dont contribute much to the torsional frame strength, so they were eliminated.
This allowed the engine to be mounted quite low keeping the centre of gravity low.
This greatly improves the bikes handling while maintaining high cornering clearance.
Even though it is a steel spine frame, and many bikes now use aluminium twin-spar
type frames (which are more rigid), some modern bikes are using the same principle
for frame technology today.

Opinion:
The bike has a definite solid road feel. It feels very 'planted'.
The bike also is very forgiving when road conditions become unstable, and has
almost no wandering or flex in the frame.
I am not sure if this is due to the frame design, or maybe because the whole bike
geometry is just well sorted.

Update:
Even though the original 1984 model had a 16" front wheel (120/80/16) with
anti-dive 38/39mm diameter forks, and a relatively narrow 130/80/18" rear, a
setup that worked quite well and was part of the appeal for a 1984 sport bike,
improvements were to come, as the industry again settled on standards for
handling and performance of modern machinery.
The A7 model has a nice fat 3"(wide) 17"(diameter) front Enkei wheel
with 120/70/ZR17 rubber.
The A7 rear was increased to a 150/70/ZR18 tyre and the wheel was 3.5"(wide)
18" diameter Enkei wheel.
The A7 also got rid of the anti-dive fork system, which I am led to believe
worked quite well, if maintained, and upgraded its forks to 41mm units, with
heavier progressive springs.
According to sources, the GPz had better handling with this front end setup.
(although I cannot make a personal comparison)

Thirdly, It has some great brakes.
It has a triple disc setup with drilled solid mounted rotors. Nice for a road bike.
The front pair are 280mm with strong single piston calipers.
The rear is a 270mm (maybe 280mm) also with a strong single piston caliper.
This allowed the bike to be ridden harder and faster, and with more confidence,
as it could now stop as well as it goes.

Update:
The A7 model upgraded the components to 300mm front 'floating' discs with
twin piston Tokico calipers.
And the rear is now a 250mm disc with a twin piston Tokico caliper.
They are reasonably light to touch, give a good controlable progressive feel,
and they do stop very very well.

Fourthly, It has a great 6-speed gearbox.
I am not sure how many bikes at the time had a 6 speed box, but it seems
common nowdays.
Changing gears is quick and reliable.
However a 'false' neutral can still occur on rare occasion.
The gearbox does give you confidence in its gear selection.
Given the wide engine power band and many gear selections, you always
have enough power no matter what gear you are in.

Opinion:
The bike also accelerates hard in any gear, and can do 6th from about 2800rpm
very smoothly.
Redline is 10500rpm. (and spins there without complaint)
Gearing on my A7 is about 25kph/1000rpm or 4000rpm at 100kph in 6th gear,
using the (150/70/ZR18 Michelin MACADAM)
 - 5th is 22kph/1000rpm.
 - 4th is 18kph/1000rpm.
 - 3rd is 16kph/1000rpm.
 - 2nd is 12kph/1000rpm.
 - 1st  is 10kph/1000rpm - and you can do 0-100kph in 1st gear
                                        in about 3 seconds flat.

NB: The 17" rear has me at about 102kph at 4000rpm in 6th gear, running
a 160/60/ZR17 Dunlop SportMax.

Fifth, It looks great (and very cool).
It rides really well, its engine is smooth, and it has a nice balance for a
225Kg (dry), maybe 250kg(wet), Streetbike.

Other things I have read and noticed:

 - Counter balancer on Crankshaft - minimising engine vibration.
 - Top-mounted starter motor.
 - Water-cooled - however it does use its thermo fan a lot when stopped,
   and in low-speed traffic.
 - Full fairing - increased aerodynamics for greatly improved high speed stability.
 - Good ergonomics - making it enjoyable for daily use, and long rides.
 - Good Screen - does the job well.
 - Great fuel efficiency - has a large 22lt (4.8ImpGal) tank capacity.
   Opinion: I have achieved 65mpg (23km/l) while touring, without trying,
   at upto 80mph (130kph).
 - Good low speed ability - engine performance is tame at low speed,
   and great agility in traffic.
 - Amazing acceleration - a sub 11 second 1/4 mile time in street trim, in 1984.
 - I am told it will crack 150mph (or 240 kph).
 - An engine in 1984 with 115bhp (engine), and A7 has 108bhp (engine).