633GC SHOP MANUAL
62
Copyright © 2005 ICS, Blount Inc.
23
This section covers carburetor tuning. Included in this section are basic settings,
idle speed adjustment, and complete adjustment.
The carburetor has been set at the factory for optimal performance and
compliance to EPA Phase I emissions standards. However, minor adjustments
may be required in certain conditions, such as when operating at high elevation
or after the saw has been rebuilt.
NOTES:
• This cut-off saws speed is mechanically governed by the carburetor. This will
prevent the saw from going above ,500 rpm. Attempting to set the carburetor
mixture to increase the speed or power beyond this limit may seriously damage
the engine.
• Always check the air filter, fuel filter, and spark plug before making carburetor
adjustments and clean or replace if necessary.
• When adjusting the carburetor, turn the screws very little – no more than /4 of
turn at a time. Minor adjustments will have large effects on the engine.
• If the carburetor has to be readjusted completely, the limiter caps must be
released before the basic setting can be made.
Basic Setting – if the carburetor needs to
be completely readjusted, see following
procedure:
A Pull limiter caps using ICS
®
P/N 7625.
B Gently turn both adjusting screws
(H and L) clockwise as far as possible.
C Turn screws counter-clockwise:
H = turn from closed
L = /2 turns from closed
Verification of rpm, with bar and no chain
Idle = 3,000 ± 200 rpm
Full throttle = ,000 ± 500 rpm
23. CARBURETOR TUNING