82 GPz question

[Guest]

Was reading this https://www.google.ca/url?sa=t&rct=j...62578216,d.cGU and this statement popped out at me
Yet closer examination showed that a fair amount of work had gone into making this 750 special. New bits included a revised cylinder head, ported and polished, and with smaller combustion chambers incorporating specially placed ridges to induce swirl. New pistons with higher domes helped squeeze the incoming fuel/air charge, resulting in a compression ratio of 9.5:1. Revised camshaft profiles and new constant-velocity 34mm Mikunis helped breathing, and an oil cooler kept operating temperatures in check.
The revised camshaft profiles doesn't go with what my Kawasaki factory manual says.All the specs are the same for all the KZ and GPz engines.Supposition without checking facts?

[Nessism]

Have read on KZ Rider and kz650.com that the later cams are hotter. I believe it, as the later bikes were faster so the power must have come from somewhere.

[srsupertrap]

The Motorcycle Classics link you have copied a lot of what Cycle World stated in their original road test of the 1982 GPz750 (hand ported heads, beefier cams etc). Cannot verify the claim the cams were different but certainly the GPz performance was. As Ed stated the later model GPz750s made more power but that just made them peakier .

[SVSooke]

I checked with the downloaded manual,the ZX750's(GPz750 from 83 on) do indeed have a hotter cam.Does the 82?I tend to doubt it.Higher output is more likely due to the increase in CR,porting and different(better?)carbs.Statement about the head casting was interesting to as it sounds like they where doing something like the Twin Dome Combustion Chamber of the GS650.Guess you would need a side by side of a 82 GPz and an earlier KZ head to see if that one's true.

[Nessism]

Just checked the manual and parts fishe, and the 1982 GPz seems to use regular 750 cams. Check the part numbers on Kawasaki.com, in the Owners Info section...http://www.kawasaki.com/DefaultFrame...HOWVEHTABS%3d1

Starting in 1983 the GPz did get different cams, which are clearly identified in the service manual as having more duration. The exhaust cam doesn't have provision for the tach drive though, so it's not a drop in replacement. Didn't check the valve springs either (too lazy). At any rate, I wouldn't worry too much about the cams. A more peaky powerband doesn't help that much on a vintage bike.

[SVSooke]

I am not looking to change the cam as I'd rather have more grunt lower in the power band anyway.While asking where there gold GPz's?Watching this vid https://www.google.ca/url?sa=t&rct=j...62578216,d.cGU I see he started with a gold GPz750.If it's factory it must be rare as I haven't seen many.Google images search reviled none so it looks like it was a custom job

[srsupertrap]

Some Canadian models were Sonic Gold

[SVSooke]

Some Canadian models were gold

OK that makes sense to me. Canadian divisions of the Japanese makes all seem to do things different than the US one's.

[Montanaman]

The lobes are shaped differently on the '82 GPz on up - it was changed to get the valve off the seat a little quicker, and it was good for 5hp on Kawasaki's dyno. My '83 KZ750 L3 had the same cam profile, but the heads didn't get the porting & polishing like the GPz's did. I think it was CYCLE magazine that opined the porting & polishing was worth maybe .10 - .25 sec in the quarter.

[Nessism]

The lobes are shaped differently on the '82 GPz on up - it was changed to get the valve off the seat a little quicker, and it was good for 5hp on Kawasaki's dyno.

How did you come by the above information? The Kawasaki service manual and the parts fishe shows the 1982 GPz750 used the same cams as the regular 750's.

[SVSooke]

The lobes are shaped differently on the '82 GPz on up - it was changed to get the valve off the seat a little quicker, and it was good for 5hp on Kawasaki's dyno. My '83 KZ750 L3 had the same cam profile, but the heads didn't get the porting & polishing like the GPz's did. I think it was CYCLE magazine that opined the porting & polishing was worth maybe .10 - .25 sec in the quarter.

How did you come by the above information? The Kawasaki service manual and the parts fishe shows the 1982 GPz750 used the same cams as the regular 750's.

The 83 and up GPz defiantly had different cams but according to the service manual the 82 did not.I haven't checked a fiche but if Ed says it's the same PN that's good enough for me.On the subject of parts who's a good Kawi supplier down in the US?One that will ship to Canada reasonably?

[Nessism]

On the subject of parts who's a good Kawi supplier down in the US?One that will ship to Canada reasonably?

I ordered from powersportswarehouse.com because they were cheap, but the service was very slow. Can't recommend them...although they were cheap.

[Montanaman]

How did you come by the above information? The Kawasaki service manual and the parts fishe shows the 1982 GPz750 used the same cams as the regular 750's.

I still bleed firecracker red - and after I wrecked my '81 GPz550, my new wife said "Not another GPz" thinking them to be inherently dangerous things. But I wanted a GPz750 or GPz1100.

So when the magazines wrote up the original GPz750, they were going over all the minor changes, and one talked about the slightly different lobes on the cams, and said that the 5 hp wasn't just moved from the lower revs to the higher revs, but there was power added everywhere.

They were comparing cam profiles from the '81 KZ750.

I'll see if I still have that mag in my collection.

Luckily for my Kawasaki came out with the KZ750 L3 in 1983, so I got my GPz after all !

[SVSooke]

I'd like to see that Montana.Seems to me the .5 CR with the port and polish would be worth the 5 extra BHP.Ed how long did that powersportswarehouse order take?

[Nessism]

Ed how long did that powersportswarehouse order take?

It took them a month to ship. When asked what the delay was at the three week mark, they blamed the weather, which I don't believe (other than maybe a day or two).