What is the Difference between "J" motor and 84 GPZ1100

Besides the obvious, such as the displacement and the Head, what are the lower end, and mid section differences between the J motor and its successor. Are any of the parts interchangeable? I also of course know about the 17mm and 18mm wrist pins. Are the crank cases the same or interchangeable? Are the cylinders interchangeable? I also know about the 1/4mm longer stroke on the newer engine, which would result in a 1/8mm taller cylinder block. Etc. Etc.

Post edited by: otakar, at: 2008/02/14 18:05

i dont know what all interchanges but ive got a set of 1170 pistons and block just waiting for a cheap 84 gpz to put them on!

To the naked eye, both cylinder blocks appear to be the same height, but I can't see a .005" difference just by looking

I have a 83 GPz1100 block that is planned to go an a J motor (998cc), but I'm still trying to get the J motor here.

I am realy interrested in the lower end differences. IE Can I put a "J" crank in a 84 GPZ case? can I Put a 84 tranny in a 81 case and so on.

otakar wrote:

Can I put a "J" crank in a 84 GPZ case? can I Put a 84 tranny in a 81 case and so on.

Yes, in both cases.
Everything will fit in your examples.
A GPZ is a J motor, just better cams,pistons etc.
I believe, (but am not sure)that early J motors have a smaller piston pin diameter than later models.

OK that sounds good. Now next question; Are the main cases the same between the sahft and the chain drive engines?

otakar wrote:

.......Are the main cases the same between the sahft and the chain drive engines?

Yes, definitely.
I think the only difference is the transmission output shaft.

Thats the ticket. I was wondering if a shafty could be converted to a chain drive system by changing the shaft drive cover system and the swing arm and wheel. I have the parts for the conversion if they fit as hoped.

I'm not certain but I think the frames are different also. I don't believe that the chain drive swingarm will bolt on the shaft drive frame.

Frames are no problem. Nothing a good torch can't cure.:whistle:

otakar wrote:

I was wondering if a shafty could be converted to a chain drive system by changing the shaft drive cover system and the swing arm and wheel.

There is a monkey wrench to your plan.
The transmission output shaft is different between the shaft and chain bikes.
You will need to split the cases and install the output shaft that allows mounting of the chain sprocket.

It is possible you could machine something to work without splitting the cases. Sounds like the kind of challenge I like..

Splitting the cases, I do not consider a "MunkiWench" Only a slight inconvenience. eBay here I come. "Here Output shaft where are you"?:lol: