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Strange headlight problem on my 1976 Honda cb750f

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Idabird

Strange headlight problem on my 1976 Honda cb750f

I have an odd problem with my headlight and looking for help. I recently converted the headlight to a h4 setup and everything was working fine until a couple weeks ago. The headlight stopped working but all others work. Changed bulb. No fix. Checked power at the plug with the bulb out hat 12v on both high and low using the ground for the headlight. So I tried another bulb and still no light. Checked the voltage at the back of the plug with the bulb in and had no voltage. Took bulb out and had 12v

TOOLS1

Re: Strange headlight problem on my 1976 Honda cb750f

Administrator

Do the bulbs work when hooked to a power source other then the headlight plug in the bike? It does sound like a ground problem though.
TOOLS

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1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)

Maz

Re: Strange headlight problem on my 1976 Honda cb750f

In reply to this post by Idabird

I suspect a bad ground connection. It's conducting enough to measure on a voltmeter, but as soon as you connect the bulb, the connection is not good enough to supply the current required to light the bulb.
Maz

'76 CB500T
'75 GL1000 'Wing
'79 CB750L
'90 FJ1200
'93 GS500E

In a little place called Bexley, Kent, UK (Just south of London!)

Idabird

Re: Strange headlight problem on my 1976 Honda cb750f

In reply to this post by Idabird

I switched the bulb with one from an old Ford focus I have. Same h4 bulb. Worked in the headlight on that. Thank you I will check out the grounds

shinyribs

Re: Strange headlight problem on my 1976 Honda cb750f

Administrator

Dumb question: isn't the stock bulb H4?