power fluctuates with RPM

[XS400HeratageSpecial]

I have a 1981 XS 400 Heritage Special & My headlight brightens and dims with the rpm's of the bike. My stock headlight did the same thing but it wasnt bright enough to drive at night to begin with. When it burnt out I replaced it by retro fitting a new halogen bulb into the lamp. When testing out the retro fitted light on the bike the light got brighter as the rpm's increased, while warming the engine and eventually leveled out. I was so happy I decided to go for a first good ride at night, but as i started to drive off the headlight got brighter & burnt out. I dont know why this is happening and don't want to pay a mecanic $80 a houre to figure it out. Somone I work with said they thought is was the stater but i dont want to buy parts i dont need. Any Ideas would be appreciated.

Thanks

 

[drewpy]

I seem to think the us models had a relay for the front lamps, you could check that out. Also I suspect that the battery is overcharging, get a multimeter on the batt terminals and there should be 13v - 13.5v @ 3k revs on DC setting.

 

[XS400HeratageSpecial]

Thanks ill check it out but should the bike be running when I do the voltage check?

 

[xschris]

yes have the engine running.

 

[drewpy]

unless you can turn over the engine by hand so it does 3000 revs!

 

[HoughMade]

I'm thinking the voltage regulator.

 

[drewpy]

I'm thinking the voltage regulator.

I'm thinking....i need a shower