8. Milling, Fitting, and Finishing Touches

LEFT SIDE AXLE SPACER:
The left side is easy.

You mill 2.5mm from the inner side of this spacer.

You take the left side wheel spacer and mill down the inside
surface by the required 2.5mm.
My neighbour has several metalwork lathes and was willing
to do the work for me.
I am fortunate, as he builds his own race cars, and modifies
and fabricates any parts he needs.
He is old school, so calculates each machining into thou.
(thousandths of an inch)
So when I say we took 2.5mm off the left side spacer,
I mean we milled exactly 2.5mm off.
He translated the required reduction into thou,
then milled down the spacer.

ADVICE:
If you are going to follow this rear wheel conversion procedure,
I guess this is the part where I have provided some measurements
as I did them, and you should still do your own measurements,
but you have to decide if you are going to get a metal work expert
to do the actual machining.
Because once you take metal off, you cant put it back on again.
If you screw it up, you will have to source new spacers or
fabricate them from scratch.

RIGHT SIDE AXLE SPACER:
The right side is a bit different.

There are effectively two spacers.
The inner most spacer next to the wheel, and the brake caliper
mounting bracket.

See the two spacers. Inner Spacer (left) and Outer Sleeve-spacer (right).

The inner spacer should not be touched.
It is recessed, again, onto the wheel bearing.
There is not enough to work with here, to mill the required
4.5mm off, and still have the spacer protrude from the wheel
bearing rubber seal. So leave it alone.

BRAKE BRACKET SPACER:
The option here is to modify the brake bracket spacer.
The brake bracket has a 'hard' metal spacer that runs through
the softer alloy of the actual brake caliper mounting bracket.
Let's call this the 'sleeve-spacer'.
The unmodified brake bracket sleeve-spacer sits almost flush,
on the inner side of the brake bracket.
But protrudes on the outer side of the brake bracket, against
the R# swingarm-swivel axle mount.

NB: The ZZR600 brake bracket has NO sleeve-spacer.
It is only a 'soft' metal axle spacer itself.

The sleeve-spacer needs to rest against the right side
(outer side) of the inner spacer.
 - Hard-metal against hard-metal.

And also the protruding (flanged) side of the sleeve-spacer
needs to rest against the R# swingarm-swivel axle mount.
 - Hard-metal against hard-metal.

The brake bracket must be able to rotate freely when the
wheel assembly is installed and tightened.

I decided to get the required 4.5mm (in thou) milled off the
inner side of the sleeve-spacer.

Mill 4.5mm from the inner side of the Sleeve-Spacer, and recess the Brake bracket.

Sleeve-spacer.

Sleeve-spacer inserted and just raised from brake bracket.

Sleeve-spacer inserted (inside view) and just raised from brake bracket.

Then, recess the brake caliper mounting bracket the required
amount (which is slightly less than the sleeve-spacer flange
width), so the now modified sleeve-spacer fits nicely through
the brake caliper mounting bracket, but protrudes just a few
thou each side to give the required hard-metal to hard-metal
contact on both sides.

When you have done this, the axle spacer work is complete.
And there are just a few more finishing touches.

BRAKE BRACKET SLIDE BOLT:
You can check when you bolt it all up, that all hard spacer
surfaces mate properly, and that the brake caliper mounting
bracket spins freely, as I said before.

You must now mill down the outer brake caliper bracket
surface, where the slide-bolt goes to prevent the brake
caliper bracket from spinning. This is where you fix the
caliper bracket to the R# swingarm.
I think it was about 2.5mm, but you can measure it.

The Original GPz900R brake bracket no longer fits when the sleeve-spacer is milled.

See where it hits the Swingarm slide-bolt bracket.

Only a few mm needs to be milled off this section.

You pretty much grind the 'flanged' section back to being
flush with the rest of the bracket.
Once this is done, the brake caliper bracket can spin a full
360deg around the axle, once the wheel is installed,
and everything is fully tightened.

I did this with a hand file. Didn't need to be perfect.

I think I ended up with another 1 mm off this.

Just a bit thinner ... Until it fits.

And finally you need to get yourself a 1mm washer to
replace the original 2mm washer, that fits inside the
axle nut, on the outer side of the swingarm.
Remember I said this is required to give you back 1mm
of axle thread you lost by not compressing the swingarm.

You only use the NEW thinner washer. (comparison shown)

It all should be done and ready to bolt up.

GPz900R - Rear brake bracket - installed.

ZZR1100 - Rear brake bracket - installed.

17 Inch Rear Wheel Bolted in Place. (left side view)

17 Inch Rear Wheel Bolted in Place. (right side view)

REAR BRAKE CALIPER:
Next attach the brake caliper.

Original GPz900R caliper and bracket, with a matching ZZR1100 250mm Disk.

I needed to move the brake caliper inward by about 4.5mm
to cater for the changes.
I just got some longer allen headed high-tensile bolts of the
required length.
I only had 3mm thick steel washers, but there is a generous
amount of room on the caliper slides, so these did the job well.

Can you see the 3mm washer - between the brake mount and caliper backet.

These washers go on the inside of the caliper bracket
between the caliper mount plate. 
I did shave a few mm from the back of the allen headed
mounting bolts, to give a bit more clearance to the disk
rotor surface.
They are now flush with the fully installed caliper plate.

CHAINGUARD:
One final modification is required for the chainguard
clearance to the new 17" tyre bead.

The 17" tyre now sits closer and lower to both the plastic
chainguard, and to the metal chainguard guide on the L#
swingarm.
I simply cut a recess in the plastic chainguard.

You need to make room for the Tyre.

So make a simple recess cut in the plastic Chainguard.

Pretty easy modification.

I also simply filed the chainguard guide on the swingarm
at an angle, and rounded the edges, to give me the clearance
I required.
Not a hard task.
No measurements, you can work this out for yourself.

Original unmodified Chainguard guide - dirty.

Next...

File a nice angle for Tyre clearance once installed.

Just hand done, with rounded edges.

CENTRESTAND:
You can do the centrestand yourself, if you want to have one.
I like having a centrestand on a bike.
It makes it easier to work on the bike, in the garage.
If you got yourself a Kawasaki GTR1000 unit, like I said,
then you should be able to work out the
clearances required. see my previous notes on this.
I have not modified my stand yet, but I do intend to do it.
I also got a spare ZZR1100 stand for about $25Aud.
I may consider using the top of the GPz900R stand, and the
bottom of the ZZR1100 stand, which has a nice wide base,
and weld them together to fabricate a better stand.

That's it !
Done.

You should now have a 17" wheel fitted into your GPz900R.

Does it look okay ?

Factory Fitted ?

Now go for a Ride.

Finished Bike... for now...

Now with K&N filters and the New carbs. (next the SS Exhaust !)

MY ADVICE:

Please note, I am not a mechanical engineer.
I am a reasonabley experienced home mechanic.
Not a qualified mechanic.
I do use people's advice.
I have learned people available for support.
I am not going to make any dangerous modifications.
I do not wish to die because I made a stupid, unsafe,
or uncalculated modification.
I may perfect the alignment at a later stage.
(add 2mm on the right, expand swingarm)
This procedure is a guide to what I did.
You must use it as a guide, and for information.
Get your work checked.
Do your own measurements.

Remember,
You can't beat Qualified and Experienced Professionals.

PS: I did take this to my Kawasaki shop for a look.
They thought it was a pretty good job too.

Thanks and Stay Safe.