Topic: Wiring problems on my 1977 CB750F1

[Stewart]

Hi would appreciate anyones help here, I am going mad, I have 2 problems, first is that my tail light does not work, brake light is fine, and tail light works when ignition switch is set to park, but not in run with side lights or main selector switch on, the other problem is the sidelight in the headlamp is not working, same situation, when ignition switch is set to park it works, but not in side light mode!!!
I have found plenty of wiring diagrams but none show the sidelight in the headlamp unit or the separation of the tail and brake light. Any help would be appreciated.

[Jerry Rxman Griffin aka MuthaF'er]

I really hate to ask this but since you didn't mention, are you using 2 filament bulbs that have 2 good filaments in them?

What is a side light??!! By sidelight, are you referring to run signal/running light? Other than a headlight and turn signal there are no other lights up front!? I have seen/heard of rear turn signals installed up front. Won't work properly due to the double circuit of running light and turn signal.

Have you used a multimeter to see where you are getting voltage? If not that would be the best way to start. Begin at the sockets then work your way backwards. If you don't have a multimeter, you need one and a cheap one ($5-$10) will do the trick.   

[Stewart]

Thanks for your reply Jerry, in my headlight I have 1 large buld in the centre, which has 2 filaments, both are working for high and low beam, then there is another small bulb  below the larger one which has 1 wire going to the centre and then a ground, this is what I am refering to as the side light, and this is the one which comes on when the ignition key is in the park position, on the handle bar switch I have 2 positions one is labeled 'P' and the switch lever goes up slightly in this position into an inset part of the groove, and the other position is 'H', which assume to mean 'Headlight'. I took the bike for an MOT recently and the guy at the garage told me that the 'P' switch position should turn on the side lights, (the smaller bulb below the main one in the headlight. this is not working, and in fact to rear light does not come on in that position either, but it is also not working in the main position so that could be a red herring.

[Jerry Rxman Griffin aka MuthaF'er]

Stewart,

Please fill in your personal info. When I saw "centre" (vs center) then MOT I realized you may have a non-US bike and I may not have the necessary help for you as your bike and the US bikes will have some differences. My bike is a US 75 F which the European countries did not receive. You first received it as a 76 F while our 76 F was a F1. In fact you may have only gotten 76 & 77 F's while our's ran from 75-78. The P on the ignition switch is indeed for turning on the parking lights and not the headlight. The US bikes do not have the extra light in the headlight. My ignition switch, which I have in my hand due to a total tear down, has, beginning at full left, lock/push (push down and turn left to lock the steering column in place), off, on, and P. Our handlebar switches have high/lo on the left switch and ignition on/off on the right switch. I'm surprised that you would have 2 different P's?! Perhaps this shouldn't be so and that's part of your problem!?      

You may need to find one of the Europen guys with a F to compare notes to. There is a separate forum for the British guys too that you may be able to go to and find a F guy. By far the best site with the most comprehensive and world model specific microfiches is www.cmsnl.com. Perhaps comparing US part numbers to European/British part numbers would help. If you find your specific bike's microfiche get the part number and I can compare it to an actual US part and let you know what you should expect from that part.    

[Stewart]

Thanks Jerry, I will check it out, I am aware of the CMS web site and I have a full parts list so I will check the part number, seems strange that you would have a parking position in the handlebar switch though.....

[Spanner 1]

Euro bikes have a small low wattage bulb as a running light in the headlight... Euro's do not run their headlight during the day! So, on park position, the 'city' running light in the h/l comes on with the tail light...... whereas here in the U.S. 'park' lights tail light only....
Stewart, check the tail light fuse ( carefully ) as on 'park' the tail gets its power from the Main fuse, not the tail light fuse.....