At last I have found a site that may be able to help me before I go completely mad. I am relieved to see that there are many other CB72 owners facing similar problems. I have a 1967 CB72 which is basically in good condition, however, I am having problems charging the battery. I have been unable to get a manual so my efforts revolve around my owning a CB160 in the 1960s.
Basically the battery continually (and quickly) drains (a new battery I was assured). The ignition light remains on all the time and increases in intensity when the bike is revved. I have replaced the old Selenium rectifier with a modern solid state one which hasn't made any difference. I note that the DC wire should be pink but mine is a braided white colour, which although passing through the ignition switch is always live. (What is the third position for the ignition switch?). I think that all the wires are intact and the alternator seems to be producing electricity as I can light a 12V led directly from the leads and the headlights blaze away when the engine is revved.
The one lead that puzzles me is the green/red striped one that comes from the alternator and seems to be connected directly to the ignition light.
Can any one head me in the right direction?
Also can any one explain the various timing marks on the rotor/flywheel. The bike is running OK with new points and plugs but I am not sure what marks to use for timing. It has a type 1 arrangement. Please help.
Masunari
CB72 chargingChargingThe green with red stripe wire is the neutral switch/light wire that runs all the way to your headlight bucket.
I have a wiring diagram for the CB77. If you want a copy, PM me. Gary '65 CL77 Owner
CB72 chargingThank you for taking the time to reply and I shall look up the article.
Have you acually checked the battery terminal voltage with a volt-/multi-meter say, after a day or two of not running the bike? It should stay above 12.5V easily. Does the motor start on the button (ie: does it crank on the starter without labouring or the starter solenoid chattering?) If you can check the voltage, as above, whilst doing so then it shouldn't drop below 10 or 11V whilst the starter is engaged. Positive answers here indicate a 'good' battery.
There is no 'ignition light'; the one in the headlamp is 'gear in neutral', as ggray says - if that doesn't go out when in gear then the neutral switch is shagged. They can be repaired - let me know. If the voltage increases substantially when the motor is revved (indicated by the brightening if the lights as you describe) then the battery is possibly on its last legs and unable to stabilise the dynamo's output. Also, it sounds like you've installed the new rectifier correctly, as the diodes would be prevent any output path if you got it wrong. I'll help you to further diagnose as you need. Dear Steve
Thank you for taking the time to reply, Since I posted the request I have gained a lot of useful information. The neutral switch was definitely new to me. It does go out when I change gear. The light is so dim at times I can hardly tell if it is on or off. It has been imposible to start using the electric start unless I boost the battery and indeed the horn also refuses to work unless it is boosted. I have bought a decent battery charger since the last message. When I attempt to charge it it gives me the message "open cell " So I can summize that the battery is indeed US. I will be buying a new one tomorrow. So much for it having had a new battery! I have just downloaded how to check ignition etc. so that is my next job. Do you know which are the various adjusting screws on the carbs. ie. slide and air screws? befoe I charge in and upset the settings ! I will keep all posted on progress. What an excellent site. Best Wishes Marcus
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