ZXR400 GPX400 Restrictor Dimensions.

[Thom]

Ok right i'm working on a theory as i plan to strangle my gpx400 with a 33bhp kit (just so i have one for my own peace of mind).

The zxr400 apparantly puts out 59bhp (44KW) at 12000RPM

The GPX400 is said to put out 59bhp (43.4 KW) at 12000RPM

They also use very similar carburettors and i expect similar jetting also.

So, here's my theory, as the bikes are using the same engine, according to kawasaki themselves, and they have the same unrestricted bhp as standard i expect they use the same size restrictor washers.

However, i have no idea what these sizes are.

Anybody know what size washers their ZXR's are using (Internal and external dia,'s) as if it's the same i can fit a set of ZXR ones i got cheaply.

Mucho's thanky-o's!
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Current Bike: 1996 Yamaha TRX850 (The Japanese-Ducati One).
Previous Bikes: 1990 Honda NSR125 'Rothmans' (The smoking one), 1990 Suzuki GS500e 'Caf? fighter' (The loud one), 1987 Kawasaki GPX400r (The quick one), 1997 XJ600s Diversion (The reliable one), 2000 Kawasaki ER-5 (The spontaneously combustive one)

[G]

[Thom]

According to various sources, including kawasaki UK (PErhaps - I emailed someone about it) the first ZXR4's used the GPX engine, also from what else ive read it was bunged straight in, no tuning or anything.
____________________
Current Bike: 1996 Yamaha TRX850 (The Japanese-Ducati One).
Previous Bikes: 1990 Honda NSR125 'Rothmans' (The smoking one), 1990 Suzuki GS500e 'Caf? fighter' (The loud one), 1987 Kawasaki GPX400r (The quick one), 1997 XJ600s Diversion (The reliable one), 2000 Kawasaki ER-5 (The spontaneously combustive one)

[G]

ZXR engine:
https://www.motociclisti.ro/kawasaki-zxr-400-zx-4r-zx4r-zx-400-lsporttouring.html
FX 400 (same as GPX):
https://gees.zenfolio.com/p442736719/h60251ee#h19610a1d

The first thing that I thought of, which prompted me to look was the carbs; as I thought, the ZXR uses carbs which are more vertically mounted (airbox under tank) compared to the GPX which has them more horizontally mounted (airbox under tank).
The engine looks more upright and generally different. I personally doubt they are the same engine or even similar.

I'm impressed you got someone to email you; usually I've been referred to a dealer who have little idea on modern bikes and none on old bike.

[Thom]

i was surprised i got a response actually. they also sent me a spec sheet 1st class which did actually arrive the very next day!
____________________
Current Bike: 1996 Yamaha TRX850 (The Japanese-Ducati One).
Previous Bikes: 1990 Honda NSR125 'Rothmans' (The smoking one), 1990 Suzuki GS500e 'Caf? fighter' (The loud one), 1987 Kawasaki GPX400r (The quick one), 1997 XJ600s Diversion (The reliable one), 2000 Kawasaki ER-5 (The spontaneously combustive one)