Which Motor

I just got a motor from a 83 750 Spectre that is need of rebuilding. My question is, would it be better to take the parts off of the 750 and build my 650 into a 810 or rebuild the 750 into a 810? Which would be the stronger engine? Any thoughts would be appreciated.

Rebuilding the 750 to 810 would be the easiest - don´t know which would be the stronger, but you can´t bore a 650 directly to 810, sleeves are not big enough, you´d need a 750 block. And the 83 750 block will not work on your 77 650 (or any pre-81 650s for that matter), you need an early 750 block that has the recesses for the camchain idler gear shafts - later 750 blocks don´t have these recesses so theres no way to make the 650 single roller cam chain work as there´s no place to install the idler gear shafts.

Post edited by: OnkelB, at: 2006/10/03 12:27

We have established that the 1980 KZ750 four block has the recesses, and the 83-85 GPz750 blocks don't (there are other differences between the KZ750 block and GPz750 block also)but I don't think we have determined what other year/models have the recesses.

It would be nice if we could

Maybe someone with the Zedder software will check the 80 KZ750 cylinder block part number and see what all it was used on (pretty please)

Being the impatient sort, I checked the part numbers at Kawasaki.com, and the part number for the cylinder block changed in 1981 models. So it looks like the 80 KZ750 cylinder block is the one to get.

Post edited by: steell, at: 2006/10/03 13:25

Well, if I can't use the jugs off that motor, can you easily convert the shaft drive into a sprocket drive? According to buykawasaki.com the output shaft #s are different. I haven't pulled the coupling off the 750 yet to see what's there.

what about swapping cranks too? then you could use the 750 jugs and run the hy-vo chain with the 650 cases

77KZ650 wrote:

what about swapping cranks too? then you could use the 750 jugs and run the hy-vo chain with the 650 cases

That's possible to do, crank/rods/ect will fit right in.