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Carburetor Adjustments & Tuning Tips
110
Adjustments for Competition
The carburetor used on your CRF should perform
suitably with the standard recommended settings
under average load, climatic, and barometric
conditions. However, to fine tune the engine’s
power output, the carburetor may require
adjustments for specific competition needs.
Optional main jets, slow jets, leak jets and
accelerator pump diaphragms are available for
your CRF. See your dealer.
Any engine or air cleaner housing modifications or
the use of an aftermarket exhaust system may
require jetting changes.
Cold Start Circuit
A very rich mixture must be delivered to the
cylinder when a cold engine is being started. When
the choke knob (1) is pulled out, fuel is metered by
the starter jet (2) and is mixed with air from the air
passage (3) (located above the throttle valve (4)) to
provide a rich mixture for starting. The mixture
discharges through the orifice (5) into the cylinder.
Hot Start Circuit
A lean mixture must be delivered to the cylinder
when a hot engine is being started. When the hot
start lever is pulled back, the hot start valve (1)
opens, allowing air to be supplied to the main bore
(2) through the hot start air passage (3). This extra
air enters the air-fuel mixture from the slow circuit
resulting in a lean condition.
Carburetor Components
(1) choke knob (4) throttle valve
(2) starter jet (5) orifice
(3) air passage
(1)
(5)
(2)
(4)
(3)
(1) hot start valve
(2) main bore
(3) hot start air passage
(2)
(1)
(3)
31KSE7100_NA.book 110 ページ ２０１９年４月９日 火曜日 午後１時１３分
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