Bolens MTD7122B09 manual ~~~:;qll~~~J, 8-C~ok~

Now open needle valve 1-1/2 turns counterclockwise and idle valve one turn. This initial adjustment will per- mit the engine to be started and warmed up approx- imately 5 minutes prior to final adjustment.

Final Adjustment-Place speed control lever in FAST position. Turn needle valve in until engine slows (clock-

wise-lean mixture). Then turn it out past smooth operating point (rich mixture). Now turn needle valve to midpoint between rich and lean. Next, adjust idle RPM. Rotate throttle counterclockwise and hold against stop while adjusting idle speed adjusting screw to ob- tain 1750 RPM. Holding throttle against idle stop, turn idle valve in (lean) and out (rich). Set at midpoint be- tween rich and lean. Recheck idle RPM. Release throt- tle. If engine w111not accelerate properly, the carburetor should be re-adjusted, usually to a slightly richer

mixture.

CONTROL ADJUSTMENTS

Proper choke and speed control operation is depend- ent upon proper adjustment of controls on the powered equipment.

To Check Operation

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Casing

Clamp

Screw

Fast~Position

' E

I '

\~' ,,\

F

Move control lever to CHOKE position. The carburetor					Throttle	Control	Adjustment
choke	should		be closed.
					Place speed control lever on equipment in FAST (high
To Adjust		Choke:
					speed) position. Loosen casing clamp screw "C," Move
Place	control		lever on	equipment in CHOKE position.
					casing	"A" and wire until lever "E" touches link at "F,"
Loosen casing clamp screw. Move casing and wire until					Tighten casing clamp screw "C." Move control to
choke	is	completely		closed. Tighten casing clampscrew. STOP		position.	Lever must make good contact with

stop switch.

SECTION 5

GENERAL INFORMATION

ENGINE DESIGN

This engine is single cylinder L-head. air-cooled type.

MODEL SERIES 281707

Bore	3-7/16"(87.31	mm)
Stroke	3-1/16" (77.78mm)
Displacement.	28.42 cu. in. (465.7 cc)
Horsepower Max. '."'..'	' .12 @ 3600	APM
Torque (Ft.-Lbs.) Max.	20.5 @ 2400	APM

The horsepower ratings listed are established in accordance with the Society of Automotive Engineers

Test Code-J607. For practical operation, the horsepower loading should not exceed 85% of these ratings. Engine power will decrease 31/2% for each 1,000 feet above sea level and 1 % for each 100 above 600 F.

In some areas, local law requires the use of a resistor spark plug so as to suppress ignition signals. If an engine was originally equipped with a resistor spark plug, be sure to use the same type of spark plug for replacement.

Major engine repairs should not be attempted unless you have the proper tools and a thorough knowledge of internal combustion engines.

TUNE-UP SPECIFICATIONS

Spark	Plug		Type		Champion	Autolite
Short~.	Plug				CJ-8	235
Long	Plug				J-8	295
Resistor		Short		Plug	RCJ-8	245
Resistor		Long		Plug	RJ-8	306
Spark	Plug		Gap			030"
Intake	Valve		Clearance.			005"-.007"
Exhaust		Valve		Clearance.		009"-.011"

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