WM 80 Repair Carburetor Inspection and Ad-
wc_tx000522gb.fm 99
See Graphic: wc_gr002904
Tillotson Dual Needle:
Both high- and low-speed mixture adjustment is required on dual
needle models. See section Operating & Idle Speeds for correct
operating and idle speed settings. For best accuracy use a tachometer
when making carburetor adjustments.
For initial carburetor set-up after rebuilding, complete the following
procedures:
8.3.6 Turn in (clockwise) high- (H) and low-speed mixture needle valve (L)
by hand until tight.
NOTICE: Do not overtighten the valves. Damage to the valve seats
may result.
Preset the fuel jets as follows:
8.3.7 Open the low-speed needle valve 3/4 revolution counterclockwise.
8.3.8 Open the high-speed needle valve 1-1/4 revolutions counterclockwise.
8.3.9 Start the engine and allow it to run at high speed for 3–6 minutes.
Check the adjustments by running the machine at full throttle and at
idle several times. Keep the choke fully open. If further adjustments are
necessary, continue with step 5.
Note: After full throttle operation, allow engine to idle one minute
before making any adjustments.
8.3.10 When making carburetor adjustments, turn the valve screws in small
increments, no more than 1/16 of a revolution (turn) at a time. Turn the
screws clockwise to lean, counterclockwise to enrich. Allow 5 seconds
after each adjustment for engine to stabilize.
8.3.11 Check the low-speed adjustment first by accelerating the machine to
high speed. If the engine bogs down during acceleration and/or dies,
the carburetor is set too lean. If the engine bogs down then accelerates
slowly, the carburetor is set too rich. Adjust low speed until good
acceleration is achieved. Re-adjust idle speed screw for required idle
speed.
8.3.12 Adjust the high speed screw to obtain the best operating speed.
Running too lean or too rich will cause the engine to run at a lower rpm
than optimal. If the high-speed needle valve is set too rich, the engine
will emit black smoke from the muffler.
NOTICE: Because the engine is lubricated by the fuel mixture, do not
lean-out the carburetor too much; the engine may overheat and
damage components.
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