Hi ,Im,about to fit a powerbox to my mates Mk3 and was wondering if anyone could give me an idea of where to fit it , also the best places to wire up to, as my knowledge of electrics is not very good , and also when it is done do i just remove the rectifier, zenor ,and capacitor and tape up wires , any help with this much appreciated Brian

I have my boyer power box stuck to the rear metal plate of the battery box with Velcro.
And yes to your other questions, installation is simple with the wiring diagram they enclose.

brf1957 wrote:Im,about to fit a powerbox to my mates Mk3 and was wondering if anyone could give me an idea of where to fit it

Anywhere where there's enough space.

brf1957 wrote:the best places to wire up to

You could disconnect the green/yellow and white/green alternator wires from the original rectifier and connect each yellow Powerbox wire to the alternator wires? It doesn't matter which alternator wire connects to which box yellow wire, as the alternator output is AC.

If the bike is still wired positive earth, connect the red box wire to the frame or another red wire.
Connect the black box wire to the brown/blue (battery negative wire).

brf1957 wrote:and also when it is done do i just remove the rectifier, zenor ,and capacitor and tape up wires

Yes, and there should be two zeners on a MkIII (one on the back of each Z plate) and you must connect the 2MC capacitor's brown/blue wires together after you have disconnected it.

The following information given by Boyer Bransden in their single phase PBOX00108 Powerbox instruction sheet appears to be inaccurate:

"Do not use with the 180 watt (3 wire) single phase alternator as fitted to the Norton
Commando electric start machines. Use the PBOX00105 or change the alternator stator to
(2) wire 180 watt."

No electric start (MkIII) Commando was ever fitted with a "3 wire single-phase alternator" as standard (or even a 3 wire three-phase alternator.) as far as I know!

Also note they go on to say that: "If your Norton has a charging warning light simulator it must not be used with the power
box, remove it. If the light control is required fit the power box type PBOX00166 with
charging light control."