Mk V earthing + or-

[Brian Cape Town]

Restoration progresses well, however when I shipped the bike from the UK to South Africa I disconnected the battery and removed it taking no notice as to whether it was + or - earth, sure in the knowledge that my earlier machines a T35 and a Mk IV were both - earth. I am now at the stage of at least considering the wiring and on examining the wiring diagram that came with the bike, where the previous owner had marked a change in colours, in fact all the wires were black with bits of coloured wire wrapped around the ends to denote his new colour coding, I see that the system is - earth.

However on examining John Holmes's excellent guide he lists a wiring diagram for a Mk V as positive earth. A closer look at my existing diagram and I find it marked as being a Mk IV.

The machine is certainly  a MkV being clearly so marked but with numbers 9228 it is quite an early model.

How can I check what indeed should be the the polarity?

Thank you Brian.

[eddie]

Brian,
           The actual wiring harness is the same for both + and - earth machines. When you come to the point of getting the bike running again, you should be able to fit the battery so that it is either + or - earth, because during the time it has been laid up, the dynamo will probably have lost it's residual magnetism - and therefore will not give any output. When you are ready to start the engine - first, remove the two wires from the dynamo, and get the engine running reliably. Stop the engine, then take a short length of wire and connect the live side of the battery to the 'F' terminal of the dynamo for about 5 seconds (there will be quite a large spark). This will remagnetise the field coils,matching the polarity of the dynamo to that of the battery (irrespective of whether it is + or - earth). Replace the original dynamo wires and restart the engine - the dynamo should then show a charge. If it doesnt, then the regulator points will probably need some cleaning/adjustment. The rest of the electrical equipment is not polarity sensitive.
         Good luck with getting the bike running again,
                                          Regards,
                                                Eddie.

[Brian Cape Town]

Thanks Eddie.

That advice is most helpful to the shall we say, the electrically challenged.



                       Regards Brian