MY SUZUKI 1400 HAS A VOLTMETER ATTACHED TO THE REGULATOR OUTPUT AND NORMALLY VARIES FROM 12.6 TO 14.6 VOLTS WHILE RIDING. LAST WEEKEND SUDDENLY THE VOLTMETER WOULD NOT SHOW ANYTHING HIGHER THAN 11.2 EVEN AT HIGH RPM ONLY A SLIGHT UPWARD MOVEMENT TO 11.6 VOLTS WAS VISIBLE. THE BATTERY DIED ON ME AFTER A 1/2 A DAY AND AFTER CHARGING I WAS BACK TO 12.6 VOLTS BUT THE VOLTAGE STAYS AT THAT LEVE;L EVEN WITH ENGINE REVVED UP. wOULD THE RECTIFIER/REG BE THE CAUSE OR COULD IT ALSO BE THE STATOR?  

HI; I have a C50 The service manual seems to point to the Reg.. You really need to do all the tests for the 1400. The c50 test may not help with your bike.
Reg voltage 14.0-15.5 V @ 5000 rpm.
Gen coil resistance OHMs 0.2-1.5 Yellow to Yellow
Yellow to ground should read as open circut.
IF this does not help Sorry ....scruffy