Specifications

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for engine performance and engine life. Serious damage to the engine can occur if
not properly adjusted.
IDLE ADJUSTMENT:
On the each side of the
carburetor, there are two
adjustment screws. The right
side screw with the knurled
head is the idle adjustment
screw. To raise the idle, turn
the screw in clockwise (in 1/4
turn increments) and rev the
engine after each
adjustment. To lower the
idle, turn the screw counter-
clockwise.
TOP END JETTING:
Indications that the engine is
running too rich (too much
fuel for the air) are:
• Engine not revving out or
blubbering at high RPMs.
• Engine will not ‘clean out’
• Wet or black spark plug
NOTE: Before changing
jetting be sure that the air
filter is properly cleaned and
has the usual amount of air
filter oil. An overly dirty air
filter can cause the engine to
run rich.
If the engine is running rich on the top end it should be leaned out. Leaning it out
can be done by:
1. Changing the main jet to a smaller number.
2. Raising the needle clip (this lowers the jet needle) one notch at a time on the
slide.
Indications that the engine is running too lean are:
• Engine cutting out on top end.
• Engine overheating and ultimately seizure.
• White spark plug
CAUTION:
It is much safer to operate the engine slightly rich as opposed to slightly lean. This is
because an overly rich engine will just run poorly while an overly lean engine will
seize, potentially causing an expensive top end rebuild and a DNF.