TOPIC:

Ed's drawings are pretty close. The extra length at the back of the Kz crankcase looks to be a few case bolts that are not really involved with mounting the engine. I think you can see the major parts of the casting seem to line up, like the transverse mounting boss at the back.

If I recall, I once compared a Kz-based gpz 750 motor with a Zx-based gpz 750 motor, and the later motor did not use one of the main engine mounting points in the front or maybe it was the back. I was puzzled by that. Maybe someone modified something, but I didn't get that impression.

I wonder if they came to a similar conclusion on the 550/600 line.

The KZ-based gpz 550 wheels are big. I mention this because it is an issue I had to contend with when lowering my oil cooler slightly (on an 81 Gpz550). I was lowering it to fit a steering damper. There is very little clearance between the wheel and oil cooler, especially on hard braking. With stock springs, the front fender will contact the oil cooler. I stiffened up the front springs and that helped. I think it would be hard to fit a full size radiator in that space, and not have some clearance issues.

Here, you can see where the oil cooler is a few inches lower to allow space for the steering damper. If you imagine the wheel traveling upward, you can see the back of the aftermarket fender would be inline to hit the cooler. With the stiffer springs, It doesn't reach that point, but if there was a much larger radiator in there, there could be a problem.

loudhvx wrote: Ed's drawings are pretty close. The extra length at the back of the Kz crankcase looks to be a few case bolts that are not really involved with mounting the engine. I think you can see the major parts of the casting seem to line up, like the transverse mounting boss at the back.

If you look at the pictures I attached to one of my post of an 81 550 crankcase and an 85 600 crankcase there's bolt holes at the end of each. Going by those pics and the info from Daftrusty I think they're pretty close. What I need to measure tomorrow is the widths of the front and rear engine mounts. If they fit inside of the frame mounts I may go for it. As far as the front end goes, I'm going with a kz750b front end and spoked wheel (same in back). I may get a little more clearance from that. Maybe not as it's not a leading axle fork like the 550D.

Made an offer on the parts bike. If I get it I'll definitely post some pictures of the engine. Loudhvx was right about the missing mount. The front bottom mount is not used. I couldn't get accurate measurements because of the fairings but nothing is in the exact same place, unfortunately.