Topic: Wiring Diagram Re: 1976 CB750F--Fixing Headlight

[Honda_Dan]

I'm trying to get the headlight (Neither high or low beam) to work on CB750F. I found this nifty diagram through the greenspun articles ( http://oldmanhonda.com/MC/wiring750K1.html ) , and was wondering if anyone could confirm whether they think it is similar for a 76 CB750F or if they know another similar internet resource.

Also, my starter motor does not work (might be the solenoid). Could this be related? Fuses appear in good order and the bulb is not blown).

Thanks guys,



Dan from New Hampshire

[SteveD CB500F]

Testing the solenoid is easy.  Just short the two terminals with a (large) screwdriver.  If the starter turns - it's OK.

If it is OK, then ground the contact on the solenoid (to simulate pushing the starter button) and see if it turns.

If it does, then the problem is wiring or the handlebar switch.

[Steve F]

The headlights run THROUGH the starter button. When you press the start button, the headlight goes off (normally, anyway) and operates the starter solenoid.  My '76 750F had a bad starter button, and the same problem.  I'd bet you have the same problem too.  I replaced mine with a small pushbutton switch from Radio Shack.  You need one that will physically fit the area, and one that is a SPDT MOMENTARY type. Make sure you get a momentary as you don't want the starter getting stuck running.  The headlight goes through the normally closed (N.C.) side, the starter solenoid goes through the normally open (N.O.) side.  As far as the circuit diagram you refered to, I can't see the circuit clearly enough to tell if it's the same as your (and my) '76 750F.

[Honda_Dan]

Thanks Steve,

Is the best way to test it before buying the new starter switch, to just bypass the switch, touch the wires and see if the starter fires?

I think the coil may be fried in the starter, as it stuck on once (4 years ago), and it had died by the time I was able to disconnect th fuse.

Also, is there any harm in wireing the headlight so it just bypassed the starter switch?


Dan

[Steve F]

That'll work. Just touching the wires will either get you the headlight or the starter to operate if the solenoid kicks in.  I wouldn't bypass the headlight part because HONDA wired it to turn off the headlight while cranking the engine over.  Less draw on the battery the better, and the coils get all that's left to fire the plugs.

[Dennis]

Steve, a question for you.
Radio Shack has a SPDT momentary push button switch that is rated to handle enouigh current to operate a headlight? I wouldn't have thought that they could build a 7 or 10 amp switch that small. I have a '75 F myself, arrived with the switch broken and a few other problems.
I used a small Radio Shack, SPST momentay PB which fit into the existing opening of the housing where the starter button used to live. The switch operates a remotely located 30 amp SPDT relay to run the starter and headlight. That load will NEVER burn the relay contacts.

[Steve F]

Dennis, your idea with the relay is great.  I was able to use the starter switch all by itself, and have successfuly used it for several years now, and is still working great.  Maybe I got lucky?  When I got the bike, the stock pushbutton was nothing but pieces inside the control.  Upon close inspection of the pieces, I was convinced that the switch parts weren't any beefier than what you would get from Radio Shack.  It's surprising what you can actually get through a switch before it really starts to self-destruct.  On my cafe' bike, I added headlight relays which brought the current through the starter button WAY down, and now all it does is operate the starter solenoid. The headlight relays work great too, and supply the light direct to the battery through it's own fuse. It's noticibly brighter!

[Glenn Stauffer]

There are also wiring diagrams on the SOHC/4 site.

See this page:

http://sohc4.us/?q=node/11

--Glenn

[Honda_Dan]

Thanks for all your help, and referring me to diagrams on SOHC web site.

I tried to take off the starter motor switch yesterday, as my theory is that is where is headlight wiring problem is from. If you read above, My electrical starter switch seized a few years ago, about a week after the headlight had ceased working.

At any rate, apparently you have to disengage the throttle cables in order to get the run switch, and the starter switch off. All that stuff is wired on pretty tight and hard to get two. Perhaps one of you guys who has taken that assembly off, could give me some advice. Also, at this point I don't really care about the electric starter. Bike starts great without it.

Also, after I tried I took apart put back together the assembly, the bike ceased to get any power (no starting, no lights.) The battery is fine and all fuses are fine. Any thoughts on what I might have done?

Dan

[jgary]

Anybody have a part number for the Radio Shack replacement starter switch?  I have half of the bike apart trying to figure out why my headlight's not working.  As usual, should have come here first.  Thanks.

John.