difference between 82 and 85 gpz 750 engines

Noobie here. can anyone tell me if there is any major differences between an 82 and 85 gpz 750 engines. I have an 85 that needs a motor and i have a line on an 82 and I wanted to swap them

yep, there is a difference. 83-85 motors are different than the 82 and earlier motors. They make more power also. 83-85 gpz motors have higher lift cams, and a better flowing head. Also, 83-85 gpz heads dont have provisions for the mechanical tach gear, as they use an electric tach. I think the 82 and earlier gpz motors are pretty much identical to the kz750 motor. If you are not too worried about the loss of power the 82 motor should be an easy and direct swap.

if you dont mind me asking, what is wrong with the 85 motor? Or did the bike not come with one? The topend from that motor is worth quite a bit if you are looking to get rid of it

the 85 i have slung a chain and broke a piece of the case. Supposedly this 82 is built. 810 kit cam port and polish. I actually havent even seen my 85 yet. My dad has it up in new york I just bought it off ebay. I kinda thinking i might swap the 85 top end onto the 82 bottom end and stick it in the 85 or maybe the 82 as the 82 has a title.

I'm not sure on the 750's, but on the 550's the part that gets damaged by the drive chain is a replaceable cover, usually. When I come across that damage, I just throw on a new cover from another motor without even taking the motor out of the frame.

Maybe the damage is more severe on your 750.

There is an 82 GPZ 750, no earlier model. It also has the electronic tach , oil cooler and 34 mm Cv carbs that the KZ750s dont have. The only major difference I know of is the better cams in the later ones but Im no expert. I do own an 82 that I bought new and still have

mtkawboy wrote:

There is an 82 GPZ 750, no earlier model. It also has the electronic tach , oil cooler and 34 mm Cv carbs that the KZ750s dont have. The only major difference I know of is the better cams in the later ones but Im no expert. I do own an 82 that I bought new and still have

mtkawboy is correct. the only thing i can add is, the 82 750 GPz had the smallest combustion chamber of the 750 Gpz's. 82 was the first year for the 750 GPz. i'm not clear as if the later 750 GPz's had larger valves.

Putting the 85 topend on an 810cc bottom end would give you a very fun bike. That setup is almost identical to my 810, and it is a blast to ride.

Thanks for the info guys. I'm gonna go pick up the 82 tomorrow. Hopefully I'll be able to get it running by next weekend. The 85 has some parts missing and the caseI beleive is brake. Dunno for sure as I havent actually seen it in real life.

Another difference is the clutch setup. On the 83-85 models the clutch cable routs to the right side of the engine, on the 82 it routes like the KZ's. The bonus of this is that you can convert the 82 to hydraulic much easier than the 83-85. Just my .02

82 GPZ has the smallest GPZ750 chmaber but 83s used the KZ750 head with 24.8cc vs the GPZs 24.9. How they picked up from the 82s 9.5-1 to the 83s 10.5-1 isnt too clear to me. Valve sizes show to be the same but then Ive read that the later ones had bigger valves. 85-85 cams have .020 more lift and 16 degrees more duration but you could swap them into the 82 motor. Thats about it for me, no gaurantees on the accuracy, just what Ive read. Do a search under GPZ 750 drag racing on Google and theres more into on the rest of the bikes upgrades, head milling, 900 ignition modules etc. Its been a good bike and still looks like new with 16,000 miles on it.

I picked up the 82 today I got some more info on the engine. the guy said it was ported and polished and cammed up.