Positive or Negative Earth

[Superflash]

Gidday all.

Have recently purchased a Tri Spark EI unit to replace the manual magneto set up on the bike.

Installing and setting up the unit in itself looks pretty straight forward and am not expecting too many dramas. Will have to install an ignition switch and fuses, but that's not too difficult.

Same goes with the DVR2 that I installed some time ago in the 6v configuration. And all I need do here to convert to 12v is to disconnect the white wire and insulate it off.

Changing the light bulbs, horn and battery to 12v is also fairly straight forward.

Where it's now going to get all prickly is converting the charging circuit to 12v in order to power the Tri Spark.

I've yet to install the belt drive on the generator, but if I understand previous threads here correctly, then the belt drive will hopefully give me enough revs on the generator to feed the 12v system. Is this correct?

I have a E3L generator that was reconditioned prior to purchase, and if what I've read is correct then it should've been set up for a negative earth wiring loom. Is this a reasonable assumption? And if so, is there any advantage either way in keeping the whole wiring system set up as negative earth or would a positive earth system be better in this situation?

Reading the installation instructions on both the Tri Spark, and DVR2, it doesn't seem to matter which way you wire up the bike. Is it really that simple?

Looking forward to your thoughts, and thanks in advance.

[muskrat]

G'day Tony.
From what Ive read both the Trisprk and DVR can be wired either way. Just make sure the dynamo is flashed to the right earth.
Cheers

[groily]

https://www.trispark.com.au/assets/files/Classic%20Twin%20V3%20Manual%20V3.pdf
If using their classic system, polarity matters. If I read it right, they're set up for + earth, but like Musky says it's reversible easily enough from a quick gander - good descriptions supplied in the link.

No guarantee the recon dyn has been set for neg earth - nor for correct rotation come to that. Best check on both points?

Belt drives will up the rpm, yup. Up to 20% from memory - I have had the SRM kit and then the one Dynamo Regulators used to do but have passed on now to other hands.
Cut-in with a standard dynamo, not fitted with finer '12v' armature and field, wasn't so very far off what it would have been originally, but still  higher than with the finer-wound bits. Which didn't bother me running a magneto, especially living way out in the sticks, but might be relevant if you run with non-LED lights on and the Tri-spark in traffic at low speeds. Dunno what the current requirement for the sparks is, but with any luck 'not a lot'.

If going 'finer-wound', the output is limited to its 5A, in fact a bit less at a running system voltage of 14-odd and a max 60W load.
I fried the only one I had of them, using a 35W halogen globe plus heated grips (another 35W) - silly of me - but haven't (yet) fried a standard dynamo doing the same things winter after winter. It's said they cant/won't survive that kind of usage for ever - but one of mine has survived over 15 years of it and umpteen miles, so I'm happy enough. If the worst happens, you can buy a whole lot of replacement dyn bits for the cost of an Alton alternator, after all! (Having said that . . .  next time out it'll be Sizzle Bang and wait for daylight!)

DVR2s always.

[Superflash]

Thanks guys.

I think I'll whip the dyno off and take it in to Mike at Mike's classics.

Trying to work all that out myself is a non event. Does my head in.

Will ask him to check that it's set up for positive earth and that it's spinning the right way.

One of the main reasons for going electronic everything is because I just don't seem to be able to understand the old school stuff

Cheers

[chaterlea25]

Hi All,
The DVR2 is either positive or negative earth, it cannot be changed over from one to the other ..
So check what's written on the one you have and stick with that

John

[trevinoz]

To check, just bridge the D & F terminals and connect your battery to the terminals and earth in the polarity which you want.
The generator should rotate anti-clockwise viewed from the drive end and will be polarised.
As John stated, the DVR2 is polarity conscious.

[Superflash]

Thanks Trev.

I can understand that... I printed off Groily's explanation and have read it a dozen times and can almost get a picture of how it all works. Tend to be a visual sort of learner and unless super basic, long written text just confuses the hell out of me...whereas pictures are worth a thousand words type of thing..

Checked my DVR2, and its definitely Positive earth. So, based on John's comment, will base everything around that.

While not 100% sure, I seem to recall the seller telling me that the generator is set up for Neg Earth. So will need to flash it to reverse the polarity.

Only thing left now to figure out is if its rotation is clockwise or anti clockwise. Looking at the belt drive instructions, it needs to be anti-clockwise. So, here's hoping that's how the bloke who reconditioned it set it up. Tried contacting him to get some info, but he's off grid for some reason.

Thanks and regards

[Black Sheep]

Tri Spark and dynamo are not usually considered the best idea. When the dynamo goes off line at low rpm it can affect electronic ignition systems due to the voltage drop. You do need a decent battery to minimise this. Magnetos are of course immune to other electrical maladies.

[groily]

Only thing left now to figure out is if its rotation is clockwise or anti clockwise. Looking at the belt drive instructions, it needs to be anti-clockwise. So, here's hoping that's how the bloke who reconditioned it set it up. Tried contacting him to get some info, but he's off grid for some reason.

Most times, repairers will follow the arrow on the body if there's one visible.

But doing just as Trev said will prove which way it works and which way it won't.
If it doesn't work the way you want, just take the end cover off and reverse  the two wires that emerge from inside from the field coil (one goes to the F terminal and t'other is screwed to earth along with one brush) OR swap the brush tail connectors over (they go one to to D and one to earth).

Sometimes one option is easier than the other owing to length of wire / brush tails, but usually it's a 5 min job and shouldn't do your head in. (Sorry, no pix!)

If you motor it using a battery, with D&F hooked together and connected to battery negative,with battery positive to the body, it should go round the same way it will be driven on the bike, and polarity will be confirmed in the process, which is quite handy.

-------------------------

Black Sheep's comment resonates with me too. Significant voltage drop can certainly mess up some (all?) electronic systems, 'tis very true. I used to have hissy fits when running a Boyer system on another bike, with a big battery and a 200W alternator even, because if battery voltage was allowed to drop owing to periods lying fallow in shed  . . . it wouldn't go. It was OK once running though as alternators don't abandon us in quite the same way at low revs.  I think BB systems are the most sensitive to this (the older versions anyway), but haven't had any other electronic unit to compare with.

[jhg1958]

I am not sure how far you have progressed with your electronic ignition. You do not need to put an ignition switch on the bike. I had this dilemma and opted for a remotely controlled relay in the tool box it works fine and saves putting an extra switch or key on the bike.

John

[Rex]

Remotely controlled by what/from where?
Seems like a level of modern complexity unimaginable by Small Heath.