Fantic Motor TZ 125 2011, User Manual

Page: 43 / 72

43
Idling nozzle and mixture adjustment screw
Controls the mixture from the closed position to an opening of 1/8 of throttle
range, but has little e ff ect on full throttle. To adjust the mixture in this range,
the air screw can be turned to change the air fl ow through the circuit, or the
slow jet can be changed to provide more or less fuel. Start by turning the
air screw. Screwing it in richens the mixture. Make changes in 1/2 turn incre-
ments. If turning the screw between 1 and 2.5 turns does not give the desired
results, change the slow jet (B) and tune up with the air screw (A).
Carburetor jet needle
The jet needle and jet needle hole together have their greatest e ff ect in the
one-half throttle range. The needle moves in and out of the jet needle hole;
since the needle is tapered, its position in the jet determines the amount of
fuel allowed to fl ow. There are fi ve grooves in the upper section of the needle
where a circlip fi ts. This clip locates the needle in the throttle valve and deter-
mines its relative position in the jet needle hole, and provides a rich mixture.
Moving the clip to the top will provide a lean mixture. Change the clip posi-
tion one step at a time. The straight area of the needle a ff ects throttle valve
response in the small openings range.
1
Position of the clip
Identi fi cation
number of needle
2
3
4
5
Test runs with the motorcycle
- Warm up the engine with the carburetor at the standard setting, and in-
spect the operating conditions of the spark plug.
- Test-ride the motorcycle with the throttle opened.
Symptoms of improper settings
If your motorcycle exhibits one of the following symptoms the changes must
be adjusted. Before attempting any changes, make sure that everything else
is in good operating condition.