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The low speed needle valve is preset from the factory for the initial starting procedure.
Do not make adjustments to it at this time.
The low speed needle valve meters
the air/fuel mixture at idle and during transition from idle to full throttle. Turn the
needle valve clockwise to lean the mixture. Turn the needle valve counterclockwise
to richen the mixture. The low speed needle valve is preset from the factory, but
minor adjustments may need to be made to suit your application: fuel used, glow plug
and environment all contribute to the setting.
Do NoT aDJUST ThE low SpEED
neeDLe VaLVe untiL aFter tHe engine Has been broKen in.
resetting tHe HigH anD LoW speeD neeDLe VaLVes to tHe FaCtory settings
There may come a time when you get the needle valve settings out of spec, resulting in poor engine performance or not even being able
to start the engine at all. If this occurs, reset both the high and low speed needle valves to their factory settings as described below:
resetting tHe HigH speeD neeDLe VaLVe
●
Gently turn the high speed needle valve clockwise until it bottoms out (fully closed).
Do not force it or you may damage
the carburettor
.
●
Turn the high speed needle valve counterclockwise (open)
3.5 full turns
.
resetting tHe LoW speeD neeDLe VaLVe
●
Open the carburettor barrel completely.
●
While holding the carburettor barrel open with your fingers, use a flat blade screwdriver to gently turn the low speed needle valve
clockwise until it bottoms out (fully closed).
Do not force it or you may damage the carburettor
. From this point, turn the low
speed needle valve counterclockwise
3 full turns
.
IMPORTANT
The factory settings listed above are for break-in. Once the engine is broken in, the needle valve settings will be
different, although these settings are good for getting your engine running again. Please be aware that you will need to retune
your engine for proper performance.
Refer to the photo at left to familiarise yourself with your engine's carburettor. All of
the carburettor settings come preset from the factory for initial starting and break-in,
but you should have a small flat blade screwdriver handy to make adjustments to the
carburettor during the break-in process, which will be detailed later.
Carburettor FamiLiarisation
The idle stop screw adjusts the closure of the carburettor barrel. The idle stop screw
should be adjusted so that the carburettor barrel stays open about 1/16" (1mm). Turning
the idle stop screw clockwise will cause the carburettor barrel to stay open more. Turning
the idle stop screw counterclockwise will allow the carburettor barrel to close more. If the
carburettor barrel stays open too far, the engine will idle very high and the clutch will never
disengage. This will damage the clutch very quickly. If the idle stop screw is closed too
far, the engine may die during idle or when you engage the brakes. Ideally, the engine
should idle smoothly, yet slow enough so that the clutch stays disengaged.
iDLe stop sCreW
The high speed needle valve is preset from the factory for the initial starting procedure.
Do not make adjustments to it at this time.
The high speed needle valve is used to
meter the air/fuel mixture at full throttle. Turn the needle valve clockwise to lean the
mixture or turn the needle valve counterclockwise to richen the mixture.
Check to ensure that the high speed needle valve is set at 3.5 full turns out from
the closed position for the break-in process.
HigH speeD neeDLe VaLVe
LoW speeD neeDLe VaLVe
Low Speed
Needle Valve
High Speed
Needle Valve
Idle Stop
Screw
1mm
Turn Clockwise
to Lean
Turn
Counterclockwise
to Richen
Turn Clockwise
to Lean
Turn
Counterclockwise
to Richen
