Troy-Bilt 31/2 HP - Manual (Page 23)

Air Cooling System Maintenance
As you mow, dry grass or chaff can clog the engine’s
cooling fins and shrouds. Clean any debris from the
engine as often as needed to avoid engine over­
heating and damage.
If the accumulation of debris and dirt is especially
heavy, it may be necessary to remove the engine
shroud every few hours and clean the engine parts
located beneath the shroud. When removing and
replacing the engine shroud, be very careful not to
bend or damage the governor vanes, linkages, or
any wires.
After approximately 100 hours of engine operation
(more often if necessary), take the mower to an
Authorized Briggs & Stratton Service Center so that
its cooling fins and shrouds can be properly cleaned.
This will help prevent engine overspeeding, over­
heating, or other damage.
Carburetor Adjustment (Engine Speed & Mixture)
We have adjusted the carburetor on your mower’s
engine to give you the best possible performance
from your mower.
The rated speed for the engine is 3100 RPM to
3300 RPM. Do not attempt to make any adjustments to
the carburetor that would allow the engine to exceed
this speed. The idle speed for the engine is 1750
RPM.
If you believe that the engine’s carburetor is out of
adjustment, please refer to the Briggs & Stratton Oper­
ating and Maintenance Instructions Manual for the
correct procedure for carburetor adjustments.
Engine Ignition System
Your mower’s engine is equipped with an electronic
ignition system. This type of system eliminates the
traditional set of points and condenser. With this
newer type of electronic ignition system, you no
longer have to perform any scheduled ignition system
maintenance (other than cleaning or replacing the
spark plug as discussed next).
If you ever suspect that the engine’s ignition sys­
tem is malfunctioning, contact an Authorized Briggs &
Stratton Service Center for repairs.
After you clean and inspect an old spark plug, or if
you are installing a new spark plug, be sure to set the
gap to 0.030 inch.
MAINTENANCE
Liquid Lock
When a vertical crankshaft engine (such as on your
mower) is tipped so that the spark plug points down­
ward for several hours, there is a chance that oil can
leak into the space between the top of the piston and
the cylinder head. If the piston is on its compression
stroke, the oil can prevent it from moving. This situa­
tion is called “liquid lock’’, because the oil isn’t com­
pressible and it “locks” up the engine.
You will notice when you have an engine in this
condition. You will be able to pull the recoil starter
rope out only a short distance. Then you won’t be
able to pull it out any farther. If you’re using the
Engine Ignition key to try to start the engine and you
think the engine is locked up, don't turn the key to
start until you’ve cleared the engine as follows, or you
could damage the starter.
Liquid lock is corrected as follows;
1. Remove the spark plug from the cylinder.
2. Slowly pull the recoil starter rope by hand until no
more oil comes out of the spark plug hole.
3. Thoroughly clean the spark plug. Reinstall the
spark plug. Reconnect the spark plug wire to the
spark plug.
4. Check the engine oil level.
5. Again try to start the engine.
Spark Plug
Every 100 hours of engine operation you should
remove, clean, and inspect (or simply replace) the
spark plug.
Inspect the spark plug for stripped threads, exces­
sive combustion deposits on the electrodes and the
interior of the spark plug, cracked porcelain, or other
damage. If the spark plug is damaged, replace it.
Refer to “Specifications” on the inside back cover of
this Manual for replacement types of spark plugs.
Whenever you clean a spark plug, don’t blast clean
it. Scrape it or wire brush it clean.
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