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7-9
BRAKES
phone: 1-800-854-3140 | 1-503-304-8899 fax: 1-800-366-7505 | 1-503-304-1899
www.jjamusements.com
MASTER CYLINDER
OVERVIEW
General information .................................................................page 7-9
Master cylinder removal ........................................................page 7-10
The single-circuit hydraulic brake system provides positive and simple stopping power for the go-kart. As the name im-
plies, the “master” cylinder is the primary control of the brakes. It contains a reservoir that is oversized for the system, by
design, to provide an extra margin of e
ff
ective use. The cast-iron body provides the best surface for the machined bore
that will provide a contact surface for the hydraulic piston seals.
The diagram shows the piston bore; note the two ports that feed brake
fl
uid from the reservoir to the cylinder bore. The
equalization port (larger hole) allows
fl
uid behind the main piston seal to equalize the chamber. The main circuit port
(small diameter hole) feeds the main master cylinder chamber. The “at rest” position of the master cylinder piston and seal
is critical. You can see that it sits just past the
fl
uid intake and return port (small hole). When the brake pedal is applied,
the piston moves a small amount and “leaks back” some
fl
uid, gives a bit of cushion to the force applied to the brakes, and
keeps
fl
uid constantly supplied to the main chamber. The back seal retains the
fl
uid in the cylinder bore. Any damaged or
worn seal will result in
fl
uid leaking out or past a seal, causing spongy feel or non operation.
It is absolutely necessary that some amount of “at rest” free-play exists. As you can see, the internal return spring must be
able to position the main seal plunger at a precise position in the cylinder bore. The push-rod-to-plunger free-play should
be 1-5mm. No free-play will cause the port to close o
ff
, even partially, and result in brake drag or lock-up.
Nothing you do at the pedal a
ff
ects clearances inside the master cylinder body until the push rod moves the main seal
piston forward.
Reservoir
Body
Cylinder bore
Cup seal
Cup seal
Return spring
Cap
Diaphragm
Push rod
Push rod cover
Intake/return port
Equalization port
Max brake
fl
uid
fi
ll,
1/4” from top