Topic: Assistance need regarding electrical issue on my CB400/4:

[tom8Toe]

Can anyone tell me if running too high of wattage bulb in the tail light can create more of a draw on the battery then what my charging system can keep up with and hide what would other wise be an easy diagnosis?

The bulb attached is the bulb I pulled out: Model seems to be 1157KLF (I'm not sure but...) S3A 38 Some of the characters seem to have been rubbed off.

[malcolmgb]

standard bulb is a '380' 5w for tail light 21w for brake light, pins will be offset for correct alignment with contacts. I believe that would be the same for US market.
Watts are a unit of power so yes if you try to run a higher wattage it would use more power and also be brighter.

[Hush]

Go buy a new bulb!
Cheapest way to tell if it is causing you grief.

[tom8Toe]

Thanks guys. I appreciate the info.

Go buy a new bulb!
Cheapest way to tell if it is causing you grief.

Yeah, I probably should have before I started replacing the regulator, rectifier, fuse box, stator unit, and brand new wiring harness (which by the way wasn't exactly cheap. But hey, I can rule out the wire harness for the most part). 

[TomC]

Hi tom8toe
     The difference between an 1157 and a "380" is 3 watts as a tail light. Big deal if 3 watts is a problem you have a bigger problem.
     I am currently running a 55/60 watt headlight. And did so before I started playing with the voltage regulator. The headlight draws 20 watts more on low beam than the stock headlight.
     I do not remember what your original problem was. There is a basic problem with the charging system. On my CB400F1 which has as I said a 55/60 watt headlight and a non stock voltage regulating system at 1200rpm the alternator is producing 2 amps, better than nothing, but the the lights and ignition system are drawing almost 8 amps. Some were between 2,000 and 3,000 rpm the alternator is producing more than the lights and ignition are using. Above that rpm the alternator can start charging the battery. Clearly any reduction in the current draw is going to help. With my current system if three quarters of the time my engine is running it is above 3,000rpm my battery stays charged but if it is a idle more that a quarter of the time the charge goes down hill. I live out out in the country so I am OK. But if I go into a city I see my battery voltage go down. 
          TomC in Ohio