P25 Series of Engines
14
6.
Starts, runs poorly
•
Starts, then dies
I.
Run the engine with a spark tester in-line between the spark plug wire and the spark plug or use an
oscilloscope and see if the spark goes away at the same time the engine dies.
II.
Check choke operation.
a. Black smoke?
b. Wet plug?
III.
Test for invisible damage to the air filter by starting the engine with the air filter removed.
IV.
Prime test immediately after engine dies. If it restarts; this may indicate a problem with fuel flow to
the carburetor. Check the gas cap, fuel line, fuel filter, and the carburetor.
•
Runs with low power output.
I.
Look for unusual exhaust color (smoke).
II.
Unusually hot muffler (may glow red).
a. Retarded ignition
II.
Mechanical bind
a. A loose ignition module can drag on the flywheel or lock it up.
b. Parasitic external load. A bind in the equipment the engine is powering.
c. Internal drag from a scored piston or similar damage.
IV.
Low compression/case leak
a. Check compression
•
Engine hard to start.
•
May start and run if prime test is used.
•
May run well at high RPMs, but will not idle.
•
“Sluggish” pick-up from lower RPMs.
II.
Flow blockage
a. Exhaust blockage may idle, but performs poorly. It usually is accompanied by an unusual exhaust
sound.
NOTE:
Just as a throttle on the carburetor controls the engine RPMs by limiting the amount of air an engine
can breathe in, an exhaust blockage will limit engine performance by constricting the other end of the
system.
II.
The muffler itself my be blocked.
III.
The spark arrestor may be blocked.
IV.
Intake blockage
a. An intake blockage up-stream of the carburetor will cause a rich fuel/air mixture and constrict the
amount of air that the engine can draw in, limiting performance. A blocked air filter is a common
cause of this.
VII. Makes unusual smoke when running
a. Black smoke, usually heavy usually indicates a rich air fuel mixture
•
Not enough air: air filter blockage or a partially closed choke.
For Parts Call 606-678-9623 or 606-561-4983
www.mymowerparts.com
Summary of Contents for 25cc
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