ZXR750 Model ID's

[Mori Man]

Something to be moved over to the forum:

Sorry no H1 photo available

H2 1990



J1 1991



SP Model K1 1991


J2 1992



L1 1993


L2 1994


SP Model M2 1994


L3 1995

[Mori Man]

Side Note for 750 users,

My GPX750R used the same motor - at the time i done some research about tuning it and while on the Dyno in standard set-up they compared it against all the other ZXR750's on there database.

Between that and what I gathered - 1st edition engines are always the best, as time goes on they refine them and power is always down so if your lookingfor a replacement lump for your bike seek a 1st edition GPX motor but swap the cam's over - they were the "cruiser" edition bike after all

BTW, my GPX went off the clocks no worries and done an actual 160+MPH used to chase my mates GPz9 stage 3 tuned bike all the way up to it's top end (actually nailed him in mid range though ) his bike was a 175+ beast that i used to get to thrash after servicing

[masterofinsanity]

cheers for the info, do you know if there were any changes to the motors from the H - L models?

[Mori Man]

cheers for the info, do you know if there were any changes to the motors from the H - L models?

From what i gathered the 1st gen' motors were the best.

They changed inlet port and some internal displacement - sorry now over 15yrs ago and the grey matter is gone

There was some talk about patching in GPz750 CDI's - these were actual hand finished engines at the time , modern machines now make the same tolerances.

Within the mapping they gave some extra boost to the cam / fuel ratio of the GPX(ZXR) that was overlooked on production - again cost analysis/fuel/performance dominance.

The GPz motors are the foundation of all modern blocks and even now a GPz750 was the top racer at the DOBAR event i listed up.

If your running FCR's on your machine:

Longer intake tubes give higher torque as well as longer funnels - matching them with tuning is the key to a great all rounder.

Short trumpets (33mm) will give great top end gains but leave your bottom end flat as a pancake, however a combination of intake and trumpet can get you a quick shifter with top end ability (excluding gear ratio's).

[WelshD1K]

i might have a picture of a h1 somewhere my dad had one . was stupidly fast for a 750 aparently )had soem cams and a race pipe)

[Ballsout Racing]

Interesting stuff. The H1 engine is definitely different form the H2. As I understand it the H2 had some of the mods they used on the H1 race engines.

If you wanted to build a ZXR750 for midrange torque/power and not so bothered with top end, would the GPX cams be a better option then?

[Mori Man]

I'm sure the GPx was better than the ZXR up to around the ton mark.

Was going to check the "family tree" but the page wont load

I'm fairly sure the H1 was a tappet engine like the GPz600 then they moved onto shim engines with sliding rockers.

On another 750 note, just had some one asking about an OW-01 , never realised only 500 were made

Sure would like a hurl on one of those babies , titanium rods, magnesium engine, rear Ohlins

[kawaman]

A lot of differences between GPX and ZXR engines.

Crankcase is mostly the same, as do the cylinder block and the gearbox, but the rest is different:
ZXR H1 and H2 have tappets above valves while GPX has rockers, so heads are completely different.
Pistons are different, matching bigger valves and higher cam profiles of the ZXR
Carburators are CVK design and are slightly inclinated
Cranckshaft main journals are different, conrods too (thus GPX crank doesn't fit the ZXR engine)
Slippery clutch (fitted to all ZXR750 and ZX7R, from 89 to 03)

Now here are the differences between the H1 and H2 models:
Bigger valves
Longer CrMo conrods
Higher compression ratio pistons
Higher lift and longer duration cams
Bigger carbs (CVK38 vs CVK36 fitted on H1)
Higher capacity airbox (small extenssion above the battery)
Different lubrication system, oil filter being included inside the oil pan as on the GPX (external oil filter on H1 model)
4 into 1 exhaust manifold instead of 4/2/1 fitted on H1 (requieres the oil pan to be different, then the GPX system was fitted)
Bigger coolant radiator

The rest of the bike has some other slight changes, some of them like the ZXR400H1 vs H2:
The swingarm design is different, the rear wheel has a bigger center that receives a bigger torque absorber and its spin axle is also bigger, the rear caliper link has a different chape (rounded on H2, squared on H1), the rear mudguard is also rounded on the H2 instead of squared on the H1, and finally the swingarm spin axle has a different design so H2 frames aren't the same than H1 frames (on RH the triangle aluminium part screwed by 3 screws is replaced by a platic part, the frame being threaded instead of the alumium part).
Talking about this the H2 frame is said to be lighter than H1 one, rigidity of H1 being innecessary too high (words of the Japanese engineer that leaded these projects)

There are also a different fuel selector,mirrors that match the bike color (black on H1) and the front of the bike receive color stripes.

From 1991 to 1995 (J/K/L/M models), the engine is completely different, with a side cam timing and different internals, the valves are rocker driven again

From 1996 to the end of production (zx7r and rr, N/P models), the engine is mostly the same but with tappet above valves and different cylinder head.