gpz750 engine fits kz650 frame?

is this true? if so what years? and any info is greatly appreciated. I'd like a newer larger engine in mine.

yes it fits just have too modify front motor mount

You´ll want to talk to Steve (Steell), he has done it on his nephews bike.

I hope he finds this thread then any more info on the front mount mods?

I have done this before, it fits easily. It was quite a few years ago I did this but I just remember having to drill one hole in the engine mount to line up with the front of the engine, It was very simple.

what year gpz's are we talkin about here? up to 82?

83-85 GPz750 in a 79 KZ650SR

I don't know why you would have to modify the front motor mount, we used washers as a spacer temporarily until we got around to making a proper spacer. You need the GPz750 igniter and the wiring harness, or use your points or 650/750 electronic ignition. We used the 650 stator and rotor to make the charging system plug and play.

If you use the BS34 carbs that are stock on the GPz750, and mount the motor in a 650 SR, the petcock will hit the top of the left hand carb, Pingle will solve that problem.

The sprocket is the biggest headache, the GPz750 uses an offset 630 15 tooth sprocket, I got lucky and bought a couple of 530 offset sprockets that were left over from a group buy on the GPz mailing list. Your options are to either find someone to make you a offset 530 sprocket or convert your rear sprocket to 630 and use a 630 chain.

The 79 KZ650SR with the GPz750 motor currently has 18 tooth front and 45 tooth rear 530 sprockets, but GPzInfested says he's going to put the 17 tooth on the front so he can do power wheelies

Personally, I think he has been spoiled by the GPz750 Turbo he bought late last year

You will also need a GPz750 clutch cable and a GPz750 throttle cable, the 650's won't work.

The 79 KZ650SR now has GPz750 suspension front and rear, with the swingarm converted to dual shock.


It would be easier to put a GPz750 top end on a KZ750 lower, and bolt that in. That way you don't have to deal with offset sprockets, the clutch cable, and the GPz750 ignition system.

Not a good pic, but the only one I can find right now, GPzInfested is installing GSXR rearsets at the moment.

well do the sprockets have the same center hole and splines? because I have a custom made 5/16 offset 18 tooth sprocket on mine and I run a revtech 18x4.5 rear wheel w a 180 tire and I'd like to keep all of this. and petcock clearance won't be a problem, I'm using a custom made frame and a sportster tank. what year engine did you use?

650 sprocket will fit, the size and splines are the same for at least the 550/650/750/1000 sprockets, although some models mount differently.

We used a 83 GPz750 motor simply because I had it.

I am about to purchase a GPZ750 engine from a fellow KZR member. In order to put the engine on my 1978 KZ650c I will have to drill a hole in the mount, get new carbs, and use my dyna s ignition. You say it would just be easier to slap the top end on the 650 bottom end but what about the different timing chains? The GPZ750 uses a hyvo chain where my 650 uses a standard bicycle type timing chain.

I said it would be easier to put the GPz750 top end on a "KZ750", not a 650

As far as I know, only the 1980 KZ750's cylinder blocks and heads still have the provisions for the roller cam chain.

And I still don't have a clue why you need to drill any holes to mount the motor, maybe the 79 SR frame is different than the others?

We converted a 79 KZ650SR and used a 83 GPz750 motor.