KZ750 vs GPZ750

Long story short my KZ 750 motor is shot. The repair shop said they had a couple of KZ 750s in stock. I just got off the phone and they said that both of them have problems, but they have a GPZ 750 that is in real good shape that they can put in. What is the difference between them. Should I let them or see if I can find a KZ?

Ooooh, baby! Do not hesitate! The one thing every bike needs is factory-reliable HP.

I don't know a ton about the differences between the basic 750 and the gpz, but I do know that the gpz is a more powerful engine with different cams and slight porting on the head (stuff I've read in other posts). So, if you can get that gpz motor in without spending a ton more money I'd say go for it!

What they said! One of the tech reviews I read quite some time ago said the original reviewers of the genesis of the 750 GPz line (KZ750R1) thought that Kawasaki had done some motor work to the head to give the reviewers a non-standard bike...turns out that all the 1982 GPz750 heads were ported/polished:) 80hp stock...should eat a stock Z1/KZ900/early KZ1000 for dinner

Definitely if they can also supply the gpz carbs, but I guess if they have the low mileage motor, I would still go for it!!

Bdog

Grab that GPZ engine before someone else finds it! View it as an improved, slightly hopped-up version of the KZ750 engine. I would do it in a flash.

I agree with everyone else. get the gpz. factory mild porting, .5 more compression ratio pistons (kz=9:1 gpz=9.5:1) better cams (higher lift and more duration) so more hp, you cant go wrong if its in good running order:evil:

Go get it

Well It runs like a bat out of hell!!! I thought I was going to put down the street but ohno I need a new tach (electronic), and bigger carbs (saving my pennies) Now for the help question. When I get the RPMs up I feel a good amount of vibration in the front of the bike, and the needle on the speedo drops to 0... as soon as I shift the needle shoots back up to where it should be. I thought that the vibration could be coming from the oil cooler (no mounting bracket on the bike), but I have secured that down with some hose clamps it is not going anywhere. I am going to take back to the shop this weekend but would appreciate some advice as to what might be causing this anomaly. Also the #3 exhaust pipe is psting a little when the bike is cold it goes away as the bike warms up. The shop told me about it before I left and said they had tried to fix it to no avail.

Thanks for all your advice...you guys rock

you could try doubling up the crush gaskets for the exhaust, they arent really reusable, but they are cheap, so a new set would probably fix the issue
what carbs are you using now? the ones from the kz? if so did you change the jetting? the gpz will need more gas IMO. did you try to tighten the speedo cable?

I am betting the "vibration" is a bad speedo cable. Swap it out, lube the new one, then try it.

if you dont mind me asking, how much did all this work cost you?