Spark Plug Inspection And Replacement; General Information - Toro Groundsmaster 300 Series Service Manual

General Information

Spark Plug Inspection and Replacement

Since air gap between center and side electrodes in-
creases gradually during normal engine operation,
check condition of electrodes at 100 hour intervals.
The correct spark plugs to use in the engine are Motor-
craft AGSF22C or AGRF22 or equivalent. Set air gap at
0.040 in. (1.0 mm).
1. Clean area around spark plugs so dirt does not fall
into cylinder when plugs are removed.
2. Pull wire off spark plugs and remove plugs from
cylinder head.
3. Check condition of center and side electrodes to
determine operating temperature of engine.
A. Light brown insulator tip indicates correct spark
plug and heat range.
B. Black or oily insulator tip indicates an excessively
rich fuel mixture, possibly caused by a dirty air
cleaner element or a carburetor that is set too rich.
C. Light gray or blistered-white insulator indicates
overheating caused by a lean carburetor setting or
incorrect spark plug (heat range too high).
IMPORTANT: A cracked, fouled or dirty spark plug
must be replaced. Do not sandblast, scrape or clean
electrodes by using a wire brush because grit may
release from the plug and enter combustion cham-
ber resulting in engine damage.
4. After setting air gap at 0.040 in. (1.0 mm), install spark
plug in cylinder head. Tighten the plug to 11 - 15 ft-lb.
Push wire onto spark plug.
General Information Page 3 - 2
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Groundsmaster 300 Series