Motorcycle Repair: 1977 Honda CB 750A, solenoid valve, honda cb

Question
Hi Rich, Thanks for devoting your time to helping folks with they're Honda questions. What size "o" rings are used for the drain screw and pilot screw on carburetors? )Metric or SAE) More importantly what role does the fuel solenoid valve play, Can it be tested to determine if it works?  I can't get this bike started, have plenty of spark where needed. Your input will be greatly appreciated.  Thanks again.  alan Thomas,  Fallon, NV.

Answer
Alan, I don't have a fische that lists the o-ring size but it's approximately 5 mm diameter with a 1 mm cross section.  The solenoid valve opens the throttle when you put the engine in gear to keep it from dying.  Does the engine die or the speed drop low when the transmission is put into gear? You can put 12 volts to it and check to see if  air will flow through it when you do.

Regards
Rich