Topic: 1971 CB350 headlight wiring question

[kck3]

I recently picked up a 1971 CB350 twin.  I am having issues with the headlight and am seeking some advice.  The headlight is a sealed beam unit and it currently does not work.  When I switch the low/high beam selector on, the tail running lamp comes on but no headlamp.  I took apart the headlight and have three wires coming out off the bulb:  green  blue   white.  Which one of these brings power to the bulb?  I know that blue is high beam and white is low beam and is green ground?  Just wondering where I should start looking for power supply to the bulb.

[Joel]

Yes, the green wire is the ground connection.  You mention switching the L/H switch on.  Does your switch have an off position?

[Johnie]

So you know for sure the bulb is 100% OK in both filaments?  If so, you could use a light tester to touch the blue and white wire and move the switch to see what comes on.  There is also a possiblity the switch is corroded or bad.  When the bulb is in the bike at least the high or low should come on.  It is hard to believe both high and low wires developed a short at the same time. 

[Raul CB750K1]

My 1972 CB350 has two light switches: one in the handlebar, the other in the headlight shell. The latter switches between off, parking and beam. In the "beam position", the handlebar switches between low and high.

The purpose of the shell switch is to switch on the second winding in the alternator. There is one winding used only for lights. If the lights are off, the winding is open -therefore not overloading the regulator. If the light is on, the winding is connected to the regulator -but somewhat compensated by the bulb load. The idea is that the regulator is not given the burden of dissipating excess power if the lights are not needed.

Hope this hints give you a clue about what to look for.

[Joel]

Ok, I think I understand.  Our US bikes are set up to have the lights on when the bike is on.

If you have a test light or multimeter, test the leads to the headlight.  With the switch in the Low position, you should have voltage between the White and Green.  With it in the High position, you should have voltage between the Blue and Green.

Have you checked all the connections to the switch in the shell?  There is probably a wire feeding power to the headlight that goes through that switch.  If it came loose, the tail light would come on but the headlight would not.

[kck3]

Thanks for the replys.  I am going to go look at it this afternoon.  I am not sure I understand about the switch in the shell.  I can only find one switch for the headlights- on the bar for  OFF  LOW  HI.

Where is the switch located on the shell?  Hope I am not just overlooking something so simple.

[Joel]

If you only have one switch, don't worry about my response concerning the one in the shell.  Do you have a wiring diagram for your bike?  Start testing wires at the headlight and work backwards until you find the problem.  Since the tail light works, it's probably somewhere between the left-hand switch and the headlight bucket or a problem with the headlight itself.