Engine Parts

1
Engine Parts
2
Air Filter

• Pre Filter in the cover
• Should be free of grit, oil gas
• Filter
• Cardboard
• Change every 25 operating hours or season
• Cannot be oil or gas soaked

3
Blower Housing

• Contains the pull start
• Covers the flywheel
• Protects against muffler burns
• Most common place to find a model number
• Housing Directs Air From Flywheel Fan To Cool
  Different Areas Of Engine, Especially Around
  Cylinder Portion Of Crankcase
• Be Sure Area Is Free From Dirt And Debris, Which
  Would Cause Overheating.

4
Brake Bracket

• Must be set before replacing on the engine
• Check the kill switch connection

5
Carburetor

• Purpose
• To atomize gas
• To give proper mixture to fuel and air
• Choked
• Air is blocked off
• You have a rich fuel mixture
• Why would you do this?

6
Connecting Rod

• The cap is torqued in in. lbs.
• Connects the piston to the crankshaft

7
Flywheel

• Contains Magnet To Induce Ignition Coil At A
  Specific Time Due To Location
• Contains Fins To Pull In Cooling Air For Cylinder
• Its Mass Carries Momentum To Maintain Engine
  Rotation During Exhaust, Intake And Compression
  Stroke.
• Has Starter Cup Attached
• Used To Transfer Rotation From Rewind To Start
  Engine.

8
Fuel Tube

• Heavy corded tube
• Different in 2- and 4- stroke engines

9
GovernorHelps control engine speed and prevents
overheating
Governor Linkage Goes from throttle control on
the carburetor to the governor arm under the
flywheel
Governor Arm Connects the governor linkage to
the internal governor paddle in the engine block.
10
Piston

• Creates Vacuum During Intake
• Causes Air Fuel Mixture To Compress
• Transfers Burn Of Fuel Mixture Into Linear
  Movement
• Forces Burnt Gases Out Of Cylinder
• Contains Piston Rings
• Seal Against Compression Leakage
• Movement Of Lubricating Oil

11
Rewind Starter Spring

• Goes in the blower housing
• Straighten it to retention it

12
Valves

• Exhaust Valve
• Doorway To Allow Burnt Air-Fuel Mix Out Of
  Cylinder.
• Must Be Able To Withstand High Temperatures

Intake Valve - Doorway To Allow Fresh Air-
Fuel Mixture Into Cylinder.
13
Armature

• Produces High Voltage Electrical Charge For Spark
  Plug
• Contains Primary And Secondary Coils Of Wire
  Along With A Transistor.
• Uses Magnetic Induction System From Flywheel
  Magnets To Produce Electrical Charge

14
Block

• Contains the Cylinder
• Valve Stem Guides
• Valve Ports
• Sump (holds oil)
• Cooling Fins

15
Breather

• Contains Reed-Style Type Breather.
• See Discussion Regarding Vacuum At Removal Of Air
  Cleaner Back Plate
• Breather Functions As A One Way Check Valve.
  Allows Crankcase Air To Exit Cylinder During
  Power And Intake Stroke, Closes To Prevent Air
  From Going Back In During Exhaust And Compression
  Stroke

16
Cam and Tappets

• Lobes
• Transfer Motion To Tappets For Opening And
  Closing Of Valves.
• Height Of Lobes Affect How Long The Valve Is
  Open.
• Gear has timing mark

Compression Release
Lobe

• Compression Release Mechanism
• Slightly Opens A Valve For Easy Starting.
• Once Engine Has Started, Mechanism Will Move Out
  Of The Way For Full Compression

17
Crankshaft

• Converts Linear Motion Into Rotational Motion.
• Attaches To A Device For Producing Work, Example
  Mower Blade, Belts, Hydraulic Pump, Etc.
• Supported At Both Ends In Cylinder Housing By
  Bearings.
• Contains An Offset For Connecting Rod.
• Offset Affects The Amount Of Piston Travel In
  Bore. (Displacement)
• Contains Gear.
• Used To Drive Camshaft.
• ½ Diameter Of Cam Gear For 2-1 Ratio
• Has Timing Mark For Proper Orientation

18
Crankshaft Parts
Counter Weights
PTO
Magneto
Crankpin or Connecting Rod Journal
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Cylinder

• Structure For Engine
• Contains Cooling Fins For Heat Transfer
• Made From Aluminum
• Some Units May Contain A Cast Iron Sleeve For
  Longer Wear

20
Head

• Incorporates Cooling Fins
• Used To Dissipate Heat

21
Head Bolt

• Always tighten in a star pattern
• If there are any longer, they go around the
  muffler

22
Fuel Tank

• Older models are metal
• Carb sat on top
• There was a pump

• Newer models are plastic
• Fuel filter inside of the tank of many
• Gravity feed now

23
Intake Manifold Tube

• Carries Air Fuel Mixture From Carburetor To
  Intake Manifold
• Constructed Of A Polymer Material To Resist Heat

24
Muffler

• Reduces Engine Noise
• Used To Direct Out Going Hot Gases

25
Oil Slinger/Governor Gear

• Paddles On Outside Of Gear Serve As An Oil
  Slinger.
• As Assembly Spins, Paddles Will Splash Oil To
  Various Areas Within The Engine.
• Contains Governor Assembly

26
Sump Cover

• Contains Surface For Crankshaft To Ride On
• Is The Reservoir To Hold Engine Oil
• Contains Governor Assembly

27
Starter Cup

• Cup Provides The Interface Between The Rewind
  Assembly And The Crankshaft

28
Valve Spring

• They look the same
• If one is stronger it belongs on exhaust
• Mark to make sure they get back on valve they
  come off

29
Valve Spring Retainers
School Engine Retainer