Motorcycle Repair: CB250G4, us bikes, fuse box

Question
Hi bill. I am rebuilding an old Honda CB250G4, 1975 model but can't find a diagram for the headlamp wiring. The bike has been sat in a garage for 10 years + so you can imagine the amount of crud that was at the bottom of the fuel tank! (Which needs a small braze at the bottom)
everything else is in really good fettle for a 31 year old so I'm looking forward to riding it as soon a possible.
Any specific problems I should look for?
Good to see someone around who likes these old machines as much as I do.
I don't agree with our recent survey in the UK to find the top 100 bikes when the Cub came first and the CB's cam 3rd, 5th and 7th!
Look forward to hearing from you.

Answer
Andrew, I have some similar info from a 1975 CB400F, but it is the US model with always ON headlights, which was a US standard starting in 1975. Being that we didn't get any CB250G4s here, only the 360T versions, I'm not sure if this info will be that helpful for you. However, the wiring colors for Hondas are pretty consistent through the years. You should be able to use a 12v test light and go backwards from the headlight connector to the headlight switch on the handlebars to find the fault. Some of the wiring connections are inside the headlight shell, but much of it is down under the fuel tank on the left side and then back to the fuse box at the rear, under the side cover. Of course, test the bulb first to see if it has failed internally, before you dive into the mysteries of the wiring harness! On a bike this old, I would check and clean all wiring connectors from front to rear, though.

For the US bikes, the headlight switch doubles as the starter switch, so when the button is out in normal mode, the headlights are ON whenever the key is ON. When the starter button is depressed, the headlight contacts OPEN and the starter contacts are CLOSED to make the starter circuit operate. Once the buttong is released, they change jobs again. Most UK and domestic machines I have seen or known about from that era had separate functions for the starter and headlights, as well as the PASSING function and/or Park light option that were not used in the US.

I agree about your assessment of the bike survey, however in terms of significance the Cubs are certainly a powerful force... just not much fun to ride in comparison with the CBs!

Bill Silver
www.vintagehonda.com