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LED running light issue

Crosscountry

CB750 New member
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Colorado
Hello, I just got a 1976 CB750 and wanted to upgrade the lights. So I installed the LED lights from Common Motor at all four corners and the rear light. Replaced the turn signal indicator and high beam indicator as well. When I swapped the oil pressure and neutral lights, they don’t work. They DO work with the OEM style lights in.

I DO have the pigtail in for the turn signal indicator to work and do have the LED flasher in.

I replaced the headlight with a 7” sealed beam LED headlight from Holly.

So right now all lights are LED except the neutral and oil pressure.

When I plug in the headlight all running lights shut off (LED light or original) If I rev the bike to about 1800 RPM they slowly build up lights to full strength. Once the RPM drops the running lights don’t go completely out but go very dim and flicker.

I do have an aftermarket combo regulator/rectifier. Using an AGM battery. I did NOT install the R/R.

The battery is showing around 14.5v when I rev to about 3-4K. Measuring AC voltage from the stator at the plug for the rectifier and I’m seeing 11vac yellow to yellow.


 

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I'm curious to hear others' comments on this. Do the blinkers and running lights have a resistor on them?
Did this problem happen before or after the was R&R installed?
 
I'm curious to hear others' comments on this. Do the blinkers and running lights have a resistor on them?
Did this problem happen before or after the was R&R installed?
Bike came with the current R/R on it. Definitely had low output to the lights prior to swapping to LED.

The LEDs aren’t supposed to need anything besides the diode for the indicator.
 
Your issue is interesting. I have a DOHC, but put LED blinkers on, front and back, plus an LED headlight and brake light, and changed my indicators to LED. I needed a resistor for the blinkers but everything else works fine. I do have to wonder if your R&R isn't pushing enough voltage.
Have you put your voltmeter on the running light circuit at idle and at 3-4k RPM? Curious if there is a difference in voltage considering revving the engine changes your symptoms.
Also, I wonder if your oil and neutral lights need a resistor, but I would check the voltage on those circuits first, too.
 
Got it sorted. Really was just needing resistors. Frustrating because Common Motor ships their kit as “ready to install”. But oh well. Got it done!
 
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