MTD Engine - Series 350/450/650
4
• Wet, black deposits on the insulator and elec-
trodes indicate the presence of oil in the com-
bustion chamber.
• Heat damaged (melted electrodes / cracked
insulator / metal transfer deposits) may indicate
detonation.
• A spark plug that is wet with fuel indicates that
fuel is present in the combustion chamber, but it
is not being ignited.
5.5. Idle speed: If applicable, is 1,800 RPM +
160
RPM, set using throttle stop screw.
See Figure 5.5.
• Idle speed is not normally critical in mower appli-
cations because the operator is not provided
with a throttle control.
5.6. Top no-load speed varies with blade length per
ANSI B71.1-1984 standard of 19,000 feet per
minute, allowing 200 RPM for safety margin:
See Figure 5.6.
• 20” blade models: 3,300 RPM max., all engines.
• 21” blade models: 3,100 RPM max., all engines.
5.7. Top no-load speed may be adjusted slightly to
meet this specification by bending the bracket
that the governor spring connects to. The
bracket is visible under the air filter.
See Figure 5.7.
Figure 5.5
Figure 5.6
Digital tachometer confirms safe
operating speed
Figure 5.7
Increase spring tension to
increase engine speed
Decrease spring tension to decrease
engine speed.
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For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983
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