Sym GTS 250 Service Manual page 222

Warm-up test:
1.
Start engine.
Remove the air injection filter.
Check the air inlet if there is air-sucking sounds during idling (should hear Bo-Bo-Bo sound).
Air filter
If no sound is heard, remove air cut-off valve, and connect a vacuum meter to air pipe to check for
leakage.
If there is no vacuum, replace reed valve and test again.
If there is no vacuum, check the air pipe for leakage, plugged or loose.
To this chapter contents
Carburetor
Exhaust muffler
Carburetor
Engine
Air filter
Exhaust muffler
18. Emission Control System
Air injection cut valve
Reed valve
Engine
Reed valve
Air inlet
Secondary air inject
filter
Cylinder head
Vacuum gauge
Air injection cut
valve
Secondary air inject
filter
Cylinder head
18-7