KZ650 wheel on KZ750 twin

I want to swap the 16" mag drum on my 750G for an 18" spoked drum. As far as I can tell the only kawis with 20mm rear axle and rear drum with an 18"rim are the z1 and KZ900. Those wheels are far more expensive than the KZ650 rear wheels I see on ebay. The KZ650 has a 17mm axle; would it be dangerous to swap for a smaller axle? the 750 twin is only 15 pounds heavier and only has 5 more claimed HP. braking would not be diminished as they use the same size drum and shoes. Would this be unsafe? I would use the 650 axle with bushings to make up for the difference in the axle adjusters.

Horsepower won't be an issue because the KZ650 has considerably more horsepower, not less than the KZ750 twin. The 1980 KZ750-G1 has 55 HP. The 1977 KZ650-C1 has 64 HP. Ed

Specs for KZ750-G1:
www.cyclechaos.com/wiki/Kawasaki_KZ750G

Specs for KZ650-C1
www.cyclechaos.com/wiki/Kawasaki_KZ650C

I can't imagine that such a small difference could matter in this case. Will the 650 axle be long enough? Could different wheel bearings allow the use of the 750 axle?

Same as TxKZ, maybe use different wheel bearings to mate the 750 axle to the 650 wheel?
But the larger axle may not work with the 650 hub collars n stuff.

hmmm. im going to look into wheel bearing swap. The drum plate would have to be reamed out to 20mm though. If i remember correctly there should be plenty of meat on it for that. thanks guys

I was thinking everything on the 650 wheel would be sized for the smaller axle.

OK so it looks like bearing #6204 will allow the 750 axle in the 650 hub. its 20x47x14. I think All that would remain to fit is ream the drum plate and sprocket carrier spacer to 20mm and see if the 750 bearing spacer compares length wise, hopefully its the same or longer; if not I will figure something out.

ha! i have been really lucky on ebay lately. Can't wait to try this swap. i already have a set of spokes that I was gonna use on my 650.

I got the 650 wheel. I had a kz1000 16" wheel sitting around so i pulled the bearing spacer out of that. its longer than the 650 so it can be trimmed down. The 650 brake plate looks like its got plenty to be bored out. My only concern is the sprocket carrier spacer. It is 25mm outside, which leaves a 4mm wall stock. if i bore it to 20mm then it will only have a 2.5mm wall. Will this be enough? Since its only job is to be held in compression between the bearings I don't see it being a problem. The alternative would be fitting a larger bearing in the carrier and making a new spacer, which i would rather not do.

Done and done. had the machinst sleeve the brake plate with steel. came out perfect. still need to powder the plate though.

Gotta love it when a plan comes together...Congrats! A couple pics when its finished? Please!

I am going to start a project thread for this 750 twin soon. I wasn't going to at first but as usual things have gotten out of hand and there is some stuff on it that i think some folks will find interesting.