Topic: '72 CB500 headlight dimming as I open up the throttle

[Kman]

Hi,

My 1972 Honda CB500's Headlight dims when I open the throttle.  Replaced the Rectifier/Regulator with a contemporary model, did not fix the problem though. I'll cut the engine and the light will shine bright like a diamond. I'll even shake the bike around while the engine is cut to see if its a loose connection in the headlamp housing and it stays lit and bright. Battery is about a year old, lithium. really stumped here. Any advice would be great. 

Love Karl

[BenelliSEI]

This is a weird one! Did this just suddenly start happening, or consistently since a rebuild or project completion??

[Kman]

Come to think of it I believe I've always had this issue. I live in the city so when I would ride at night I was mostly on lit city streets.  I recall Last year being in traffic and noticing that my light would dim in the reflection of the car in front of me. Honestly I think I forgot that that was one of the issues with this vintage Honda.  I wrenched on the bike this past winter and installed clips and changed some other cosmetic things.  At one point the whole front end was dissembled but threw everything back together and it started right up. Really stumped here. I'm actually gonna look over things right now. Any input would be greatly appreciated

Thanks for responding
Karl

[Kman]

This is a weird one! Did this just suddenly start happening, or consistently since a rebuild or project completion??

OK Update.  This is super weird. I removed the front of the light from its housing and attached a small 12v light bulb to the wires leading to the bike.  Started the bike and the light turned on but would flicker if I moved it around by the black plastic wire harness. So I just rushed out and bought new connecters and threw them on and attached the light to the wiring AND DID NOT screw the front of the light to the housing. Started the bike and it worked perfectly....Thought problem was solved. Screw the front of the light back onto the housing and I tried it one more time and back to the same problem....as I open the throttle the light dims.  Remove the front of the light from the housing and start it up again and no problems at all.  I'm very very very very confused..

[RAFster122s]

Many will run a new ground wire from the headlight bucket to a bike's frame ground to ensure they have a good headlamp bucket ground. If you ground in the headlamp bucket fails it can try to ground through the headstock bearings which is not good.
David

[Kman]

Many will run a new ground wire from the headlight bucket to a bike's frame ground to ensure they have a good headlamp bucket ground. If you ground in the headlamp bucket fails it can try to ground through the headstock bearings which is not good.
David

How do I add a ground wire to the headlight bucket? Plus the bucket looks and feels plastic.. I added a wire to where the coils connect to the frame and ran it into the bucket and attached it to varies parts of the light and it would ground fine. But once I just place the light onto the bucket without even screwing it in I'll open the throttle and the light will dim and or cut out.  Sometimes I will have to give the light a little hit with my palm to get it up again.  This is the weirdest thing..

Please Help....I want to ride at night and pick up women

Karl

[RAFster122s]

Yes, the bucket is plastic, was using the term or phrase to refer to running a ground wire from the battery or other chassis ground to the ground wires in the headlight bucket. This will ensure you have a good ground for everything getting terminated and connected in the headlamp bucket.

Are you certain you have the wiring connected to the headlamp directly?  I have seen lamps not properly wired illuminate partially but not dimming upon revs as you describe.
Are your terminals clean and are the connections tight? A connection that improves with a smack from the heel of your hand sounds like you have loose terminals. The headlamp uses a spade style disconnect whereas nearly everything else in the bucket is a bullet connector.  If you remove the terminal from the connector block with a small jeweller screwdriver and then clean and carefully tighten up the quick connect female connector (without closing down the opening so much as to make it nearly be impossible to fit the connector on the back of the lamp) you will have improved the electrical connection.
The other possibility is you have a short or break in the wiring that is improving with the jolt.

[bryanj]

What you are describing is almost certainly a poor connector or switch

[tlbranth]

What you are describing is almost certainly a poor connector or switch

I agree

[TwoTired]

Please Help....I want to ride at night and pick up women

Karl

Free tip to save you time.   If you pick them up, you usually just have to tip them over again later.

[Kman]

update....Replaced all the wiring to the light with new connectors, but having the same issues when opening the throttle. All the wiring is correctly connected and the switch on the handlebar is brand new. I ordered a whole new light with new wiring and bucket.  Will connect and will post the results.

[Kman]

Replaced the headlight with a new one with new wiring and it seems to work great.  Thanks for all the help, I am now able to ride at night safely and pick up women.  see attached.......booya

Thanks Again

Karl

[jgger]

So the new headlight made you strong enough to pick up 2 women at once? Kinda like Popeye and spinach,  cool!😁

[ekpent]

 Can we go riding together sometime ?   

[Don R]

 Sometimes these things will work out in a way we didn't expect and can't explain. Can be the same with a headlight.