Briggs & Stratton Vanguard 430000 User Manual page 75

6. Hold throttle lever against idle speed screw
and readjust idle speed to 1500 RPM, or
equipment manufacturer's specification.
NOTE: If carburetor is equipped with an idle mixture
limiter cap, install at this time.
7. Position limiter cap (B) so that stop(s) on the
limiter cap are at mid point between stop(s)
on carburetor body and press into position.
10
Automatic Choke Carburetor
The automatic choke consists of a vacuum choke
break and a thermostat. The Intake manifold
vacuum activates the vacuum choke break which
partially opens the choke plate, to prevent over
choking while the engine is being started. A vacuum
limiter, located in the vacuum line, regulates
vacuum to the vacuum choke break.
The thermostat contains a Positive Temperature
Coefficient heater (P.T.C.) and a bi-metal spring
which opens the choke plate gradually as the
engine is running. When the keyswitch is turned
"ON," the battery current activates the P.T.C. heater
which heats the bi-metal spring.
The P.T.C. Heater is a heat sensitive
semiconductor porcelain. As the P.T.C. heater
temperature rises, resistance increases, which
regulates battery current to the heater and
maintains the proper temperature for the bi-metal
spring.
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