Suzuki UG110 2021, Service Manual

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2-10 PERIODIC MAINTENANCE
AIR BLEEDING THE BRAKE FLUID CIRCUIT
Air trapped in the brake fluid circuit acts like a cushion to absorb
a large proportion of the pressure developed by the master cylin-
der, thus interferes with the full braking performance of the brake
caliper. The presence of air is indicated by “sponginess” of the
brake lever and also by lack of braking force. Considering the
danger to which such trapped air exposes the motorcycle and
rider, it is essential that, after remounting the brake and restoring
the brake system to the normal condition, the brake fluid circuit
be purged of air in the following manner:
• Fill the master cylinder reservoir to the upper end of the in-
spection window. Replace the reservoir cap to prevent dirt from
entering.
• Attach a hose to the air bleeder valve, and insert the free end
of the hose into a receptacle.
• Bleed air from the bleeder valve.
• Squeeze and release the brake lever several times in rapid
succession and squeeze the lever fully without releasing it.
Loosen the bleeder valve by turning it a quarter of a turn so
that the brake fluid runs into the receptacle; this will remove
the tension of the brake lever causing it to touch the handlebar
grip. Then, close the valve, pump and squeeze the lever, and
open the valve. Repeat this process until the fluid flowing into
the receptacle no longer contains air bubbles.
NOTE:
While bleeding the brake system, replenish the brake fluid in the
reservoir as necessary. Make sure that there is always some fluid
visible in the reservoir.
• Close the bleeder valve, and disconnect the hose. Fill the res-
ervoir with brake fluid to the top of the inspection window.
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" "
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Air bleeder valve: 7.5 N.m (0.75 kgf.m)
5
Handle the brake fluid with care: the fluid reacts chemi-
cally with paint, plastics, rubber materials, etc.