"Headlight" Light coming on at high RPMS

[highsidednb]

Howdy Folks

78 xs650 SE running Pamco ignition

This problem started a few days ago but rarely, now it seems full blown:

When the bike is at higher rpms (over 4000+) the "Headlight" light (part of the three lights between the Speedo and Odometer) comes on and the headlamp dims. It's still on but just barely. This problem became full blown last night (argh!) and I bogged home from work just to keep the light on...

Does this mean low power going to the headlight?

Should I check the brushes on the alternator?

Or is this a low battery issue?

I'm assuming that more power is required for faster firing so less juice is going to the other electrical systems.

Thanks for any help!

[pamcopete]

high....,

Change the brushes first. If they are marginal, they tend to fail at higher RPM's because they bounce on the slip rings. The book says the minimum is 1/4" but a more realistic number is 3/8". We could spend a lot of time debating the issue, it's just easier to change the brushes and then see what you have.

[xulf13]

Yep, just went through this myself, got a set of brushes from mike's xs and solved my charging problems. My bike no longer wants to die on me and the horn is loud and clear. I had the same issue, were I had to turn the headlight off to make it home. My inner brush was about or a little less than 1/4"

[xulf13]

Oh, and get some fine sand paper (I used 800 grit) and sand the rotor rings till they look like a new penny.