The document discusses two-stroke engines that are commonly used to power small machines for farming and landscaping. It describes the basic cycle of a two-stroke engine, including the intake, compression, power, and exhaust strokes. Key aspects like the inlet, transfer, and exhaust ports are explained. The governor device is also summarized, which automatically controls and regulates the engine speed under varying loads.

1. TWO STROKE ENGINE
CYCLE

2. Two Stroke Engine
• Used to provides power for small machines for farms
or in horticultural work
• Examples of 2 stroke engine are hand operated hedge
trimmers, hand operated chain saws, small rotary
cultivators, grass cutters and horticultural sprayers
• Valves are not normally fitted in 2 stroke engine,
instead opening known as ports are arranged in the
walls of the cylinder

3. • Inlet port – where the carburetor is attached
and fuel/air enters the crankcase
• Transfer port – where compressed fuel/air is
transferred from crankcase to combustion
chamber, ready for compression stroke
• Exhaust port – at the end of power stroke
the piston uncovers the exhaust port and
spend gasses escape

5. The Intake Stroke
The piston moves down, inlet port closed and
induction port opened
• This downward movement of the piston creates a
partial vacuum and air rushes through the
transmission port into the cylinder

6. The Compression Stroke
• The piston moves up, 2 events is involved;
• Induction port and exhaust port closed on
compression of a previous charge, a partial vacuum is
created in the sealed crankcase
• The piston uncovers the inlet port and air rushes
through the carburetor taking fuel/air mixture with it
into the crankcase

7. The Power Stroke
When the piston is in Top Dead Centre, the
spark plug sets fire to the mixture which burns
and expand, and in doing so forces down the
piston

8. The Exhaust Stroke
The piston moves down again, 2 events
involved;
• The exhaust port open so that the spent
gasses escaped
• The inlet port closed and induction port
opened on compression the fuel/air mixture
into the cylinder

9. Engine Governor
• The governor is a device which automatically
controls the speed of the engine under varying
load.

10. Function
1) Maintain a selected speed
2) Limit the slow and fast speed
3) Shut down the engine when it over speeds

11. • Governor on the engine automatically
regulates speed at whatever setting you
select on the speed control (throttle lever)
• If engine machine is operated much faster
than the top speed specified, wear increases
rapidly
• If operated much slower, less power is
available and operating costs increases

12. Operation of Governor
After you set the speed control lever, the job of
the governor is to adjust the amount of fuel-air
mixture so that the engine speed remains the
same even though the load varies
The governor must be sensitive to speed changes
The governor is mounted on the engine camshaft
where it is directly affected by any slight in
change in engine speed

13. THANK YOU