JTG JT250 2012, User Manual

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24
Air-fuel mixture
An optimum petrol-air mixture will enable you to obtain the
maximum performance from your engine. For this purpose,
the amount of air and fuel entering the carburettor must be
adjusted. A good way discover the quality of the mixture is
to inspect the spark plug. If the spark plug has a light brown
colour, the mixture is correct; if it is black there is an excess
of fuel, and if it is white there is an excess of air, in both
cases the mixture entering the engine is incorrect.
To adjust the amount of petrol reaching the engine, you
can modify the position of the main jet, which has a scale
where the larger numbers indicate greater passage of
petrol. You can also control the mixture with the air
adjustment screw. Screwing in to enrich the mixture and
vice-versa.
ADJUSTING THE TICK OVER
There are two screws on the carburettor that can be used
to adjust the tick over: The air adjustment screw and the
tick over screw, that will enable you to change the speed of
operation if necessary.