Specifications

17
MAIN MIXTURE
SCREW
17
18
** NON-ADJUSTABLE
NO CHOKE
PRIMER
* ADJUSTABLE
MIXTURES, CHOKE
SMALL WIRE (DRILL BIT)
HOLE IN BRACKET
HOLE IN SPEED
CONTROL CHOKE
ACTUATING LEVER
HOLE IN CHOKE
LEVER
LOW SPEED
ADJUSTMENT SCREW
IDLE MIXTURE
SCREW
Engine Speed and Mixture
Adjustments
3-5 H.P. Vertical Shaft Engines
NOTE: Starting and operating problems may exist
when engines are used at high elevations (over
4,000 feet above sea level). In cases where a fixed
main carburetor is used, refer to Bulletin 110 for
correction. Engines which are identified as
compliant with CARB (California Air Resources
Board) or EPA (US Environmental Protection
Agency) regulations can NOT be changed from
their factory jetting unless specifically
authorized.
Before making any speed or carburetor adjustments
be sure to adjust the governor and control bracket.
See Governor Section of the Booklet.
To adjust the speed control bracket, determine
whether the carburetor is an adjustable type, then
proceed.
Some carburetors may have a choke lever which is
operated by the speed control bracket. To adjust the
speed control bracket for full choke operation, loosen
the speed control bracket mounting bolts and move
the speed control lever to the high speed/full choke
position. Next insert a small piece of wire through
the hole in the speed control bracket, choke actuating
lever, and the choke lever (diag. 18). When all three
holes are aligned tighten the mounting bolts.
Once the speed control bracket is adjusted, the
main and idle fuel mixtures can be adjusted. Start
the engine and allow it to warm up to normal operating
temperature (3 - 5 minutes). Set the speed control
to the HIGH or FAST position, then turn the main
mixture adjustment screw in (clockwise) slowly
until the engine begins to run erratic (lean). Note the
position of the screw. Now, turn the screw out
(counterclockwise) until the engine begins to run
erratic (rich). Turn the screw in (clockwise) midway
between these two positions. This will be the best
setting.
Set the speed control to the IDLE or SLOW position.
Adjust the idle mixture screw following the same
procedure used to adjust the main mixture
adjustment.
NOTE: SOME CARBURETORS HAVE FIXED
MAIN JETS. THE ABSENCE OF THE ADJUSTING
SCREW INDICATES A FIXED JET AND NO
ADJUSTMENT IS NECESSARY.
After adjusting the fuel mixtures, engine speeds can
be adjusted. The correct operating speeds are
found on Microfiche card 30 of the Tecumseh Master
Parts Manual, or the computer parts look-up program
(Part Smart). On engines with adjustable carburetors
(diag. 19 and 20) the high speed adjustment will be
in one of two places. The first location is on the
speed control lever (diag. 19).
SPEED CONTROL
MOUNTING BOLTS
HIGH SPEED
ADJUSTMENT SCREW
19