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NOTE: As part of the initial preparation procedure, it is necessary to bring the unit to
operating temperature, and with a voltmeter connected to the battery, proceed to adjust
the idle speed until you get a reading of 12.5-12.8 volts at the battery.
Technical Guide for Keeway 50cc Carburetors
Keeway America uses two primary forms of carburetors. A mechanical slide type is
used on the 50cc units, and a constant velocity (CV) style is used on the 150cc four-
stroke units.
This guide will demonstrate the proper method of adjusting these carburetors in
efforts to achieve maximum performance and reliability. In addition, this guide will
provide basic trouble shooting skills when dealing with carburetion issues related to
rough running or poor performance.
50cc units:
Mechanical slide units are used. The throttle cable is connected directly to the throttle
slide, pulling the slide open. The slide is returned by an internal spring.
Two direct adjustments can be made to these carburetors:
The idle stop screw controls the closed position of the throttle slide. Turning it in
(tightening) raises the slide, turning it out (loosening) lowers the slide.
The second adjustment is the idle airscrew. The carb body is ported to allow airflow
AFTER the throttle slide. The idle airscrew controls airflow through this port. The
mixture is “enriched” when the idle airscrew is turned in (clockwise), and “leaned” when
the screw is turned out (counterclockwise).
Further adjustments can be made to “internal” components. Those adjustments will be
covered in a later bulletin.
For proper operation, and “clean” running, the carb setup of the 50cc units is critical.
These units should be set with the idle stop screw at the minimum opening possible, so
that they are running on the idle setscrew almost exclusively for base idle.
The factory setting for the idle airscrew is 1 ½ turns out from seated, plus or minus ½
turn. Small adjustments should make a LARGE difference in the running of these
units at idle. For example, no more than ½ turn in or out should dramatically affect the
idle speed and smoothness. If this does not occur, the idle stop screw is preventing the
throttle slide from closing properly, and the unit is running off the main jet circuit. This
will result in rich running, and fouling of spark plugs in rapid fashion.
