1985 K100RS Alternator

I've been adding accessories to my (almost) vintage K, twin 50 watt driving lights, heated grips and an electric vest for those cold rides.

Is the OE alternator adaquate, or should I move up to a 50 amp retrofit?

I believe that you should upgrade to the 50 amp alternator. I did my 91K100LT back in 92 after I found out that the 33 amp alternator couldn't keep up with two 45 watt electric vests and trailer lights. Your description of what you are adding is more than that.

I think you should be fine at highway speed. Poking around town would be a bit more dicey.

House loads (headlight, fuel pump, rear brake light) are about 120 watts.
Heated jacket and grips are 100 watts.
Driving lights are 100 watts.

The 33amp alternator puts out about 460 watts. Put a voltmeter across the terminals of your battery when everything is on, and see how many rpm it takes for the voltage regulator to kick in and limit the re-charging at the battery. Then you'll know what kind of engine rpm you need to maintain.

Thanks for the calculations

Jon - Somewhere I had learned the calculations you outlined, but for the life of me could not remember them.