1. TYPES OF SMALL ENGINES Two stoke- two cycle engine Four stroke- four cycle engine Stroke= movement of the piston within the cylinder

2. TWO STROKE ENGINES Two stroke advantages Don’t have valves Quick power- fire every revolution Lighter/cheaper All orientations- no issue with oil delivery Two stroke disadvantages No lubrication system- shorter life Expensive oil/less efficient fuel

3. FOUR STROKE ENGINES Four stroke advantages More power Longer lasting More efficient with fuel/oil Four stroke disadvantages Complicated Heavy More expensive Limited orientation

4. BASIC CYCLES OF A 4 STROKE Intake- piston goes down, valves open Goal: Air/fuel mixture enters cylinder Compression- piston heads up, valves close Goal: Creates pressure Power- piston pushed down, valves closed Goal: Spark ignites gases Exhaust- piston moves up, valves open Goal: Exhausted mixture pushed out of engine Repeat!

5. IGNITION SYSTEM

6. PURPOSE Produce a spark within the spark plug Ignites air/fuel mixture Timing is essential

7. ELECTRON THEORY Electrons travel in orbits around the center of an atom Electrons carry a negative charge Protons carry a positive charge Neutrons carry no charge

8. Conductors allow electrons to move from one atom to another easily. Electrons travel when a circuit is complete & there is a difference in charge

9. PRODUCING ELECTRICITY Mechanically- generator run by water Chemically- batteries Statically- lightning

10. MEASURING ELECTRICITY Amperes- rate of electron flow Volts- force that causes electrons to flow Ohm’s- resistance to electron flow

11. MAGNETS & ELECTRICITY Magnets have north & south poles Opposite attract Magneto system- Electricity can be made through magnets

12. MAGNETO SYSTEM Armature the armature is shaped like a capital "U". The two ends of the U point toward the flywheel. A primary coil of perhaps 200 turns of thick wire wrapped around one leg of the U A secondary coil of perhaps 20,000 turns of very thin wire wrapped around the primary coil Breaker points A pair of strong permanent magnets embedded in the engine's flywheel.

13. STEPS IN MAGNETO SYSTEM 1. Magnets fly past the U-shaped armature, Creates a magnetic field Small amount of current in coils

14. A breaker point opens. This switch breaks the flow of current through the primary coil and causes a voltage spike (of perhaps 200 volts). The secondary coil, having 100 times more turns than the primary coil, amplifies this voltage to approximately 20,000 volts Sparks instant that breaker point opens

15. SPARK PLUG Center electrode- runs through middle Carries high voltage current to the spark gap. Jumps gap Creates spark Ignites air/fuel mixture