Headlight wiring

[Mick Milakovic]

Hi All,

I want to hook up a Preston Petty headlight on my '75 harescrambler.  There is a white, yellow, and green wire.  Which goes where?  Also, what volts and watts do I get?  I remember Don Roth saying in his member profile he blew a lot of bulbs, so I want to get it right.  Thanks in advance,

Mick

[Rocket]

Mick
The yellow is the headlight wire, 35 watt.
Rocket

[TGTech]

Mick,

The Motoplat ignitions were rated as a 6 volt magneto for the lighting, but that was only if the engine stopped reving at 6K. If it went over that, then the voltage rose. If you spin the Motoplat ignitions to 10K, the voltage in the lighting goes all the way to 9 volts.

The way that we ran the systems, was using 12 volt bulbs, and powered both the headlight and the tail light off the yellow wire. That didn't provide a whole lot of lighting at low RPM, but it would get you through the check in process. Carl Cranke and Eric Jensen found a way to get more lighting out of the system for the Baja events. They used a 12 volt, 55 watt headlight bulb, and hooked the yellow wire to the hot side of the bulb and the green wire to the bulb's ground terminal. That gave them 56 watts and worked for them. It still didn't make a lot of lighting at low RPM, but it did work when the engine was running up in RPM.

The Motoplat lighting wires were rated at 35 watts for the yellow wire, 21 watts for the green wire, and 5 watts for the white wire. The yellow was designed for the headlight, the green wire for the brake light and the white wire for the tail light. If your ignition has a red wire instead of the white wire, then the green wire is 18 watts and the red wire is the 5 watt wire.

Dane

[Mick Milakovic]

Rocket and Dane, thanks so much, and see you at Mid-Ohio!

Mick

[Rain Man]

Dont forget too, the digital voltmeters dont work so well on these older bikes, digital wasent around quite yet...
 You need to use the ole analog meters from radio shack to get a good reading, ya the 1 with a needle. For a change, the old tools still work  

Raymond
 Down East Pentons