rear axle discussion at mid ohio

When viewing the pre-production Z1 at the Z1 enterprises tent, I mentioned that the rear axle was in backwards. After we looked at some other Z1's it was assumed that it was in correctly. After getting home and checking my original parts book and checking at Kawasaki.com I again say that the axle is incorrect and the nut should be on the chain side, not the brake side. For the purest's sake, what is the correct direction that the rear axle should be installed? Nut on chain side or brake side?

tfh903 wrote: When viewing the pre-production Z1 at the Z1 enterprises tent, I mentioned that the rear axle was in backwards. After we looked at some other Z1's it was assumed that it was in correctly. After getting home and checking my original parts book and checking at Kawasaki.com I again say that the axle is incorrect and the nut should be on the chain side, not the brake side. For the purest's sake, what is the correct direction that the rear axle should be installed? Nut on chain side or brake side?

As delivered from the factory, 1973 Z1 rear axle nut is on the right (brake) side, as also shown on page 24 of the original Z1 Owner's Manual, and where it was located on the brand new Z1 which I purchased in 1973 (or was it late 1972).

I don't know about the "pre-production" model.

Good Fortune!

Good Fortune!

Patton, I checked my owners manual (see your pics), and factory service manual (first pic) and found the nut on the brake side. But the parts book (second pic) and the Kawasaki.com (third pic) show it to be on the chain side.

hmmm... wouldn't take my PDF files

The parts diagrams also shows the brake side axle spacer on the outside of the sprocket, so that puts the kabosh on that theory. Looks like they grouped the brake side spacer and the castle nut on the wrong side od the hub. Wouldnt be the first mistake in those diagrams.

Dont believe any books or crap you hear, the nut is always on the chain/left side to prevent "torque freeing" which can happen if the bearings fail while the bike is at speed/under load, in its usual direction of travel of course :laugh:

If the nut is on the other side, a sudden failed bearing gnurling into the shaft can shear the cotter pin and spin out that axle faster than you can say "OH SHHHHIIIII!!!!!!""" SPLAT.

Manufacturers seem to forget this point at times... ask dirt bikers who dont maintain there machines - a few have experienced this phenomenon :laugh:

TeK9iNe wrote: Dont believe any books or crap you hear, the nut is always on the chain/left side to prevent "torque freeing" which can happen if the bearings fail while the bike is at speed/under load, in its usual direction of travel of course :laugh:

If the nut is on the other side, a sudden failed bearing gnurling into the shaft can shear the cotter pin and spin out that axle faster than you can say "OH SHHHHIIIII!!!!!!""" SPLAT.

Manufacturers seem to forget this point at times... ask dirt bikers who dont maintain there machines - a few have experienced this phenomenon :laugh:

Very interesting subject. Of course you are correct; the nut belongs on the sprocket side. I have a '77 KZ650-C1, not a Z1. The early KZ650 service manuals show the nut on the brake side the same number of times they show the nut on the sprocket side. The later manual has been corrected and with only one exception shows the nut on the sprocket side. The Kawasaki Assembly & Preparation Manual shows it correctly - sprocket side. The factory shipped the bikes crated up with the rear wheel already installed, and they (at least the KZ650-C1) were shipped with the nut on the sprocket side. That's how mine arrived when new. I suspect the other models were set up the same way when new. Ed

Patton wrote:

tfh903 wrote: ...As delivered from the factory, 1973 Z1 rear axle nut is on the right (brake) side, as also shown on page 24 of the original Z1 Owner's Manual, and where it was located on the brand new Z1 which I purchased in 1973....

The 1973 Z1 which I purchased brand new in 1973 off the Kawasaki dealership's floor had the rear axle nut on the right (brake) side,

The 1976 KZ900-B1 LTD which I purchased brand new in 1976 off the Kawasaki dealership's floor had the rear axle nut on the right (brake) side.

The 1973 Z1 and 1976 KZ900-B1 LTD were purchased at different unrelated Kawasaki dealerships in different towns.

I don't know what the Kawasaki Assembly & Preparation Manuals for Z1 and KZ900-B1 LTD and later large Kaw fours might happen to say about which side the rear axle nut is supposed to be located.

Per Dave Marston's Developmental History of the Z1:

THROUGH THE WHEEL RAN A 20MM ZINC PLATED AXLE. THERE WAS ANOTHER ALLOY SPACER BETWEEN THE BRAKE PANEL AND THE RIGHT HAND SIDE OF THE SWING ARM.
THE THREADED END OF THE AXLE PROTRUDED THROUGH THE RIGHT HAND SIDE OF THE SWING ARM AND WAS SECURED WITH AN 18MM ZINC PLATED CASTLE NUT AND THICK WASHER. THIS WASHER WAS AVAILABLE IN TWO WIDTHS, 4.5MM AND 6MM. THIS ALLOWED ANY EXCESSIVE THREAD TO BE TAKEN UP. THIS WAS THEN SECURED WITH A 4MM X 35MM COTTER PIN.

The Z1~KZ900 FSM clearly shows throughout on pics and diagrams the rear axle nut on the right (brake) side. As does the earlier mentioned 1973 Z1 Owner's Manual.

The 1977~1979 KZ1000 FSM "mostly" shows the rear axle nut on the left (sprocket) side, however the drawing on page 106 shows the nut by the sprocket and the threaded end of the axle by the brake rotor (go figure).

As a practical matter, and regardless of the dreaded "torque freeing" risk :ohmy: -- guessing ranks right up there with getting struck by lightening while riding risk -- and with the vast majority of 4>1 exhaust systems exiting on the right which enables quick and simple removal of the axle from the left without requiring removal of the muffler or exhaust system -- I (along with other dare-devils :lol: ) recklessly continue with the right side axle nut, tightening and loosening it with a large crescent wrench, and quickly and easily removing the axle from the left to properly maintain the bike, including rear axle and bearings.

And BTW, to secure the castle nuts in both the torgue bar and axle, a hitch pin clip (of the appropriate size) is imho superior to a cotter key. Not only does the hitch pin clip look better, it is less apt to draw blood while detailing the bike.

Good Fortune!

They probably began putting the axle nuts on the sprocket side beginning with the 1977 models after having received complaints from thousands of riders whose rear wheels fell off. :woohoo:

650ed wrote: They probably began putting the axle nuts on the sprocket side beginning with the 1977 models after having received complaints from thousands of riders whose rear wheels fell off. :woohoo:

Yes :laugh: , at first they tried to keep a lid on all the escaping axle reports :ohmy: by noting that the wheel chain adjusters would help keep the axle in position despite a loosened nut, and that the axle would tend to remain in position regardless of a lost nut, at least until the rider suspected something amiss in the rear end such as horrific grinding noises or a weaving sensation, which warning signs would allow the bike to be quickly slowed from 160 mph to 28.7 mph before the threaded end of the axle pulled away from the swing arm -- that would be down to 31.6 mph if both front and rear brakes were applied -- followed by instantaneous loss of rear wheel support.

Good Fortune!

Wanted -- a reverse threaded rear axle (and castle nut to fit) so the nut can safely remain on the brake side immune from "torque freeing."

Those lucky few with Denco or other less common 4>1 exhaust systems exiting on the left side, may wish to consider retaining the standard threaded rear axle with nut on the left side.

Good Fortune!