1. Two-Stroke Engines
Two-stroke engines are used only in applications where the motor is not used very often and a fantastic power-to-weight ratio is important Lawn and garden equipment

2. What’s the Difference?

3. The Basics A two-stroke engine: Is an internal combustion engine
Converts gasoline into motion
Is the most common car engine type
2 piston strokes per cycle
1 crankshaft revolutions per cycle
Chain saws, leaf blowers, Trimmers, Snowmobiles, Dirt bikes
Mopeds, Jet skis, Small outboard motors, Remote controlled planes

4. About 2-strokes Less moving parts No valves
Oil is mixed in fuel for lubrication
engine can operate at any angle
Spark plug fires during every piston stroke!
Hotter, faster, lighter than 4-stroke
Wedged piston increases air movement for intake & exhaust
Low fuel efficiency & increased emissions
Lighter, simpler, cheaper

5. Operation of two-stroke engine
Piston travels up
Intake & Compression
Piston travels down
Power & Exhaust
Plug fires EVERY piston revolution
Requires proper amount of back-pressure
Great power to weight ratio
Twice power in half the time

6. Intake & Compression stroke
Intake.  The fuel/air mixture is first drawn into
the crankcase by the vacuum created during the
upward stroke of the piston through the reed valve.
Compression. The piston then rises, driven by
flywheel momentum, and compresses the fuel
mixture.  (At the same time, another intake stroke
is happening beneath the piston).  

7. Power & Exhaust/Transfer Stroke
At the top of the stroke the
spark plug ignites the fuel mixture.
The burning fuel expands, driving
the piston downward.
Exhaust/Transfer:
Toward the end of the stroke, the piston exposes the intake port, allowing the compressed fuel/air mixture in the crankcase to escape around the piston into the main cylinder. This expels the exhaust gasses out the exhaust port, usually located on the opposite side of the cylinder. 

8. Operation of Two-stroke
How Stuff Works Link
Things to watch:
Spark plug firing
Piston acting as a valve
Where air/fuel/oil mixture enters

9. Why aren’t they used in cars?
Wear out much faster
Poor lubrication
Hotter & faster
Increased wear
Two stroke oil is expensive
4 oz/gallon
1 gallon every 1,000 miles
Inefficient
Poor fuel economy
Increased emissions
Oil burning
Unburnt fuel leaving engine

10. Mixing Gas & Oil 2 stroke oil is different than 4 stoke oil
Never substitute 4-stroke oil in a 2 cycle engine
Mix to manufacturer recommendation
Generally located on the gas cap or tag
Too much = fouled plugs & poor performance
Too little = poor protection, increased engine wear
Modern 2 stroke oils need to be mixed lighter on vintage implements.
Synthetic blends require less oil but are more expensive

11. TCW-3 Quality oil will have a rating on the label.
This means the oil has been tested and meets regulations
Avoid oils that have not been rated

12. How Much Oil do I Need? Look at the side of the bottle OR
(Gallons x 128) / Desired Mixture
= Ounces to add

13. How much oil do I add if I have a 5 gallon gas can that is half full to reach 40:1 mixture?

14. Generate a list of pros & cons with your partner!