z1 900 motor in kz650 frame?

just wondering if it could be done? with ease?

It can....

Most things can BE DONE. You have to consider more things about combining these two before getting any more ideas.

Firstly, even if the engine fits in the frame, odds are the mounting tabs WILL NOT match up, you will have to weld new ones, or just weld the engine to the frame, which would not be suggested unless you know EXACTLY what you are doing.

Secondly, the 900 is considerably more powerful than the 650, you must take into account the added stress to the frame, will the 650 be able to ride smoothly and resist twisting at high speed/accleration? Remember, the 650 swing arm was a weak spot, it will probably get uncomfortably bendy under the torque of a 900cc.

Hope this helps, there is LOADS more you have to think about first as well, and planning is the ESSENTIAL stage to do and do well before beginning such an unconventional project.

There are (or was) at least a couple of members that have KZ1000 motors in 650 frames, I think one was in the UK. If you search the archives there may be more info there.

Here's a link to a build with a Z engine in a 650: Project Z

and a pic of another:
.

Go for it...

Frame without title should be really cheap from junkwayd so if you need to cut and weld a lot, you can do a trial run on something you won't mind mangling.

Trying to stuff a kz1000 police motor in a GPX600 frame here.
Will have to replace down tubes and add new mounts.
Ordered some tubing this week.

Here's some pix with measurng tape.

FWIW the GPx swing arm pivot is very close to width of the stock arm on the police bike. Looks like easy swap with welded tabs for shocks. The tree looks like a straight bolt on with no mods other than moving the bearings over. Stem is the same length and diameter. Worst case, if I can't get the motor in the GPX frame, I can move the arm, forks, and wheels over to the police frame.

If anyone needs a GPX600 engine, minus the head and ignition pickup, or parts...the one in the photo above available for swap or cheap (REAL CHEAP). Donor bike was running until PO let water freeze in the head and crack it. He kept the head when I got the bike.

-Duck