Dear All,

I do have a 1982 T140ES (the electric start was removed by PO though) with Boyer ignition, and discovered that she has positive ground.

As per my understanding/reading, from about 1979 the T140s were negative ground..!!?

So now i am wondering if this would be the issue of the bike not charging properly and having all sorts of smaller electrical issues.
I can only guess that some PO (or workshop by accident?) changed the bike from negative to positive ground.

So now the big question is WHAT has been changed to work on positive ground, what has not ?

Just assuming that PO only put the battery in the wrong way (positive ground), what would have happened?
Would the bike potentially still run/work or would it not ?
Would the Zener Diode work or not ?
Would the rectifier work or not ?
Would the Boyer still work ?

Essentially i would like to return the bike back to negative ground and i have found a few tips to convert a positive ground bike to negative ground, however now i am faced with converting a (wrongly) converted bike back ...

I guess my main question is: what happens (could happen), if i just went and changed the battery around again, just swapping the positive and negative and not touching anything else (rectifier, zener, coils and boyer)?

Thanks for your thoughts/ideas!
Fom

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fom

Fom,

To change from -ve to +ve ground, the PO would have had to:

Change the rectifier
Change the Zener
Wire the Boyer differently
Change the leads on the battery terminals.

If on a -ve earth machine you just change the battery leads around, the zener should conduct, and blow the fuse. If the Zener was burnt out or removed, the alternator would tend to discharge the battery, and lots of heat would be generated, burning wires around the rectifier and alternator. If the Boyer was not rewired to suit, it would also have big problems.

You'll cause the same damage if you just swap the battery leads back - if the bike has been truly wired for +ve ground.

I would suggest you get the wiring diagram, photocopy it to A3 size, and work though it wire by wire - highlighting those that have been checked as you go.

Check the part numbers on rectifier and zener, making sure you have the ones you need for a -ve earth bike. Grab the wiring diagram for the Boyer off their website, and ensure wiring is set up properly.

Or you could take it to a an auto-electrician experienced with British bikes.....

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Per Ardua Ad Astra
(Through difficulties to the stars)

Thanks OzBloke,

unfortunately as i expected.....ah well, that is the whole point of the exercise.
However seems hard to come by workshop manual and parts list for '82 models.
All the manulas/lists i can get my hands on still show the +ve ground configuration, i.e. printed prior 1979 (or when the changeover actually happened)...

Edit: actually just realised that i do have the 1982 parts catalogue, just missing the workshop manual/wiring diagram

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fom

First of all, as already said get a wiring diagram ,,

Do not fit a battery either way round. Run leads from a battery via a little bulb (bulb in series with the lead) to one connection, and a straight wire to teh other, whichever way round you want it to run. switch everything off, the bulb should not light.

With this setup you are less likely to damage anything as you test throught the circuits.
Check you have a zener that works, check the rectifyer works.. etc. one thing at a time. Do not be afraid to disconnect stuff to isolate the different circuits. ( normally i would advise marking the disconnected wires....)

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A wise man learns from his mistakes..
A genius learns from other peoples mistakes.

Thanks panda,

this will be good for the coming "wintermonths" then.....

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fom