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Pit Stop Performance

Parts and Accessories

Machine Shop and Engine Building

Cylinder Boring and Honing

Displacement options.
A Kawasaki Z1, KZ900 or KZ1000 air cooled four cylinder motor
is one of the most versatile motorcycle motors ever built.
That is why it is still with us today.
It is the small block Chevrolet of motorcycles.
A stock cylinder block can be resleeved and bored up to 1261cc or 78mm.
That is an increase of 358cc over the original 903cc motor
or a total of 40% increase in displacement.
Once you step up to an aftermarket block, the displacement
can be increased to 1500cc or an increase of 66%.
All of that is without changing the stroke.
I have been building these motors and performing machine work
on them since I bought my first Z1 in the summer of 1974.
I have over thirty five years of experience and almost all of it
has been devoted to the air cooled four cylinder motor.
The question is frequently posed to me about what is the
optimum size of motor to build, and what is the cost of each option.
We will start at the lowest cost option and work our way up.
A stock 903cc cylinder (Z1 or KZ900) has 66mm pistons.
These blocks have thick cylinder walls and can be bored up to
71mm using all of the stock components.
This yields a displacement of 1045cc.
If you would like to leave the cylinder so that it can be bored again,
to extend it’s life, then you have the option to go to 70mm or 1015cc.
A stock 1015cc cylinder (KZ1000 up to 1980) or 998cc cylinder
(KZ1000 1981 and later) does not come stock with as thick cylinder walls.
These cylinders can be bored up to 72mm.
This yields a displacement of 1075cc.
Some manufacturers advertise that a KZ1000 cylinder can be
bored to 73mm or 1105cc.
I have had bad luck with this in the past and would not recommend it to anyone.
Depending on the type of pistons you select and the type of motor you have,
the piston kit for 1015cc, 1045cc or 1075cc will cost from $440.00 to $460.00.
The piston kit comes complete with rings, wrist pins,
circlips or Teflon buttons, head gasket and base gasket.
Boring costs $150.00.
So your total will be $590.00 to $610.00.
If the motor is to be used on the street, any of the above options
has my strong recommendation.
All can be operated under the standard conditions that a
stock motor can be operated under.
The increase in displacement and compression will cause the motor to
run hotter when there is not a continuous flow of air around the cylinder.
However, as long as the motor is not allowed to sit motionless
for extended periods of time, no damage will result.
Next comes the option of resleeving.
Once sleeves have been installed in the motor,
the size can go from 1105cc to 1261cc.
In order to get the oversized sleeves to sit into the upper crankcase,
it will have to be bored also.
In order to bore the upper case, the bottom end will have to be
disassembled and the cylinder studs will have to be removed.
However, removing the cylinder studs is not that big of a deal,
since with the increase in displacement the prudent thing to do
is replace them with heavy duty versions.
So, if you choose this option, what size motor should you build?
There is an old Pit Stop Performance saying that goes
“there is no modification you can make to a small motor
that you can not make to a big motor”.
The simple translation is that your money is best spent on displacement.
So, if you are going this way, my recommendation is to build a 1261cc motor.
The cost of all piston kits is at $440.00 to $460.00.
Sleeves cost $259.00.
The machine work is $340.00 and includes removing the old sleeves,
boring the block for the new sleeves to an interference fit,
heating the block and installing the new sleeves,
seating the sleeves on a 15 ton press, resurfacing the top of the cylinder,
boring and honing the new sleeves to match the piston kit.
This comes to a total of $1039.00 to $1059.00 and $40.00 more
if you want copper o’rings installed in the top of the sleeves.
It is another $60.00 to bore the upper case and
$30.00 to remove the cylinder studs.
So, you could spend up to $1149.00 on this option.
I would only recommend this option for a race motor.
Or, at least for a street fighter that is only ridden sparingly
on the street to get to the location of the race.
The reason for this is that the motor will get hot in a hurry.
The large displacement guarantees it.
In addition, the cylinder will seap oil.
That is because when the cylinder is bored for the oversize sleeves,
there are places where the aluminum gets completely removed.
This does not affect function since the primary purpose of the cylinder
is to keep the sleeves where they belong.
But if the motor is operated on the street as a daily rider,
it gets to be a pain because it takes constant upkeep to keep the motor clean.
The final option is a full out racing cylinder.
An MTC big block, and piston kit ready to go costs $1308.85 to $1328.80.
Available displacement is from 1327cc to 1500cc.
It is another $60.00 to bore the upper case and $30.00 to remove the cylinder studs.
You already know my recommendation.
Prices quoted above are not an offer to perform the work
at a particular price. They are presented as examples of
how to compare your options.


Pit Stop Performance head, cylinder and case refinishing procedure.
The following is the procedure followed for refinishing cast exterior engine parts.
The procedure as written is to apply a silver finish to the parts.
The procedure can also be used to apply a flat black engine finish (1973 Z1)
or the semi gloss engine finish (1978 Z1R).
The only change is the paint that is applied.
The parts are first cleaned thoroughly to remove any grease, dirt and oil.
Following cleaning, all holes are blown out with compressed air.
In preparation for glass beading, all of the threaded holes must have bolts installed.
This is to keep glass beads from being packed into the holes.
It will not prevent glass beads from entering the holes, but it will prevent
a large quantity from entering the threaded holes.
Next the part is bead blasted using a coarse abrasive.
I use Skat Magic which leaves a pretty rough finish.
This will remove what is left of the factory paint and provide a
clean porous surface for painting.
Next all the bolts are removed and the part is solvent cleaned again.
While in the cleaning solvent, a tap (the correct size for each thread) is run into each
threaded hole.
This will loosen any glass beads which entered the holes, as well as clean up any
damaged threads.
Following the thread chasing, WD40 is used with a tube on the nozzle to clean out
the threaded holes.
Push the tube all the way to the bottom of the holes several times to completely
clean out the holes.
Continue cleaning with solvent to remove all traces of the WD40.
When the solvent cleaning is finished, remove the solvent using soapy water.
I like to use Dawn dishwashing detergent.
It cuts grease and oil well.
Once this is complete, the part should be rinsed with water.
Finally, the part is dried using compressed air.
Each threaded hole should be blown out.
A thin blower extension should be used so that the compressed air can be introduced
at the bottom of the threaded holes.
That way the loose material can be forced out the holes from the bottom.
Once this cleaning is complete, the part is ready for painting.
Heat the part to 500 degrees Fahrenheit,
While still hot, apply Harley Davidson high temperature silver paint
(part number 98660-78) if the finish is to be silver.
This is very critical.
By applying the paint hot, the adhesion is vastly improved.
This coat of paint will look similar to a glass beaded surface, it will retain a porous
Allow the part to cool to room temperature.
The second coat of paint is applied at room temperature.
This application will give you the shiny deep silver finish that you desire.
Allow 24 hours to pass.
Finally, heat the part to 350 degrees Fahrenheit for two hours minimum.
This final step will cure the paint and toughen it.
After the part cools, it is ready for assembly.

Engine Building

Engine building services. can build you any type
of motor you like.
From an almost completely stock vintage Z1
motor to a fire breathing 1197cc street fighter or
road racing motor.
A completely refurbished motor will have the
cylinder, head, cases, oil pan, H-cover, oil pipe
and transmission cover all refinished in baked on
high temperature silver, flat black or semi gloss
The head will receive a complete valve job with
new silicone bronze valve guides, new Viton valve seals,
new APE HD valve springs and a resurfacing.
The piston kit will be a new MTC forged
aluminum set of pistons with wrist pins, rings,
teflon buttons and gaskets.
The cylinder will be bored and honed to match
the new piston kit and it will be resurfaced.
The crankshaft will be welded.
The transmission will be bead blasted, visually
inspected at 14X magnification and undercut.
The cam chain and every part that it comes into
contact with will be new.
All seals, all o’rings and all gaskets will be new.
The starter motor will be refurbished with new
brushes and a freshly machined commutator.
The fiber clutch plates will be new and the metal
plates will be bead blasted.
The clutch springs will be replaced.
The ignition timing advancer will be rebuilt.
A new dyno rubber grommet will be installed.
All the covers are either polished or refinished
depending on the wishes of the customer.
The bolts for the covers are new stainless steel
allen head cap screws.
The motor will be meticulously assembled and
the camshafts degreed.
The motor comes with a steel stand supporting it
at the motor mount locations.
Crating is available for shipping by truck or
Contact us at with your specifications to receive a quote.


Porting, Kawasaki Z1, KZ900, KZ1000 & KZ1100. port work is not called
“porting and polishing”.
It is called “porting” because there is no
My thirty five years of work with a flow bench has
proven to me that polishing serves no useful
Polishing will not yield any higher flow numbers
on the flow bench than no polishing.
For this reason, I am not going to waste my time
and your money polishing.

Stage I Porting:
Increase flow by 15% - 20% over stock.
This level of porting uses stock sized valves and
stock sized carburetors.
This port work must be performed with a valve job
and valve guide installation.
On the intake, most of the port work is from the
valve guide to the valve seat, for that reason, the
seat must be as large as the valve diameter allows
in order to obtain the full increase in flow.
On the exhaust, the entire port is reshaped, again
having the seat as large as the valve will allow is
the only logical way to start.
The port work comes complete with a flow chart
for one intake port and one exhaust port.

Stage II Porting:
Increase flow by 25% - 30% over stock intakes
and 20% - 25% over stock exhausts.
This level of porting uses over sized valves and
over sized carburetors.
This port work must be performed with a valve job
and valve guide installation.
The port work is from the carburetor manifold to
the valve seat on the intake and from the valve seat
to the gasket surface on the exhaust, the seat must
be as large as the valve diameter allows in order to
obtain the full increase in flow.
The port work comes complete with a flow chart
for one intake port and one exhaust port.
Contact us at with your specifications to receive a quote.

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