Yamaha TT-R90 Manuel D'atelier Du Proprietaire page 350

CARBURETOR HEATING SYSTEM
INSPECTION STEPS
Use the following steps for checking the possibility of the malfunctioning carburetor heating system.
Check entire carburetor
heating system for connec-
tion.
Check thermo switch.
Check carburetor heater.
Check CDI magneto.
Replace rectifier/regulator.
NOTE:
Remove the following parts before inspection.
G
1) Seat
2) Fuel tank
Use the following special tools in this inspection.
G
Pocket tester:
YU-3112-C/90890-03112
CARBURETOR HEATING SYSTEM
OK
OK
OK
Lighting coil
OK
No good
No good
No good
No good
6 - 17
– +
ELEC
Repair or replace.
Replace.
Replace.
Replace.