Husqvarna SM 50 / 2011, Workshop Manual

Page: 69 / 150

F.3
Ed. 01-09-2010
ENGINE
ADJUSTMENTS / SETTING
CARBURETTOR SETTING
Original setting
Carburettor is originally set for an altitude of approx. 500 m above sea level, a temperature of approx. 20°C, for a mainly offroad use,
and for premium gasoline available in the central European area (NO 95), mixed with 2-stroke oil.
Information for setting change
You shall always start from carburettor original setting, with the following preliminary conditions: perfectly clean air filter, exhaust system
and carburettor. Based on the past experience, it is recommended to make any change by varying main jet, idle jet and carburettor
needle jet only; any change to other components of the carburettor will not give any remarkable result.
GENERAL RULE: high altitude or temperature ................................................lean mixture
low altitude or temperature .................................................rich mixture
WARNING
- Use premium gasoline (no 95) only, mixed with high-quality 2-stroke engine oil. Other types of fuel can cause damage to the engine,
and will also make warranty null and void.
- Use high-quality 2-stroke engine oil of well known brands, only.
- A too low oil level or a poor quality oil lead to engine early wear and, in the worst case, even to irreparable damages to the engine
itself. Too much oil, on the contrary, results in high exhaust grad of smoke, and soot deposits onto spark plug.
- Should you wish to get a lean mixture, proceed with extreme care by reducing jets by one number at a time in order to prevent
piston overheating and seizure.
Should engine operation still be uneven after setting change, then the possible cause could be a mechanical failure at the
ignition system.
Basic indications on carburettor wear
Throttle valve, taper needle and main nozzle get worn very easily due to engine vibration. This could thus result in carburettor mal-
function (ex. mixture enrichment).
Idle speed - A
Operation with closed throttle valve. Rpm value is checked by mixture ad-
juster screw (1) and idle speed adjuster screw (2); adjust with the engine hot,
only. Turn screw to slightly increase engine rpm. Turn it clockwise to increase
engine rpm; turn it counterclockwise to decrease engine rpm. Turn screw to
achieve a steadier and more constant engine operation (basic setting of air
adjuster screw = open by 3.5/3 turns). Turn screw again to take engine back
to standard idle speed.