The OEM ignition test is over...

This morning I removed the OEM ignition that I had installed some days ago for "curiosity purposes" and reinstalled the TriSpark.

In one way I preferred the OEM - the bike's response was a bit sharper off the line with the timing set at 28 BTDC for both ignitions. I'm sure that was due to the fact that even though the Trispark is similar to OEM as far as the ignition advance, the OEM is still quicker to full advance.

In fact, I would have kept the OEM in except for one thing...battery charging. With the OEM ignition and the Alton/Podtronics, charge voltage didn't get above 13V until nearly 3k RPM. I switched out the Pod with the old Lucas rectifier/Zener and the voltage went up a couple of tenths but still not all that great.

I reinstalled the TriSpark and charge voltage immediately was 13.2V at idle (around 1100 RPM).

So the TS is back to stay - just wish it had the more aggressive advance curve of the stock AAU. I think I'll do the old hot-rod timing trick to see if I can get a bit more urge - advance the timing till it pings then back it off 2 degrees. Of course, if that ends up with kickbacks on start-up, that's no good either. Oh well, life's full of compromises!

Does the lower voltage/higher current matter?

Admittedly, with a regular flooded battery, the stock system is (just) adequate and heck, that was always a concern back in the day (Cue all the Lucas jokes). But that level is inadequate for a Shorai battery, which I use. Obviously, I could go back to a regular battery and the OEM system would be fair to marginal - like it was in 1973. But I like the Shorai and it's been a great batt, lasting (so far) three times longer than any other moto battery in any bike I have owned.

But I did like the response of the points/AAU!

Hmm, maybe I'll just go buy a regular battery and deal with replacing it every couple of years!

Could there have been something wrong with your points setup, causing unusually high electrical loading?

I can't say that's impossible but everything was connected as per the OEM setup - once I sussed out some wiring changes that I had made but forgot about.

The ballast resistor showed the correct resistance. The points capacitors were the ones that I had removed in 08 so I suppose they could have been bad but I don't think that has any affect on current draw and there was no sparking at the points so it appears the caps were OK. Turning on the ignition with a voltmeter connected to the white power wire that supplies the ignition system resulted in an immediate voltage drop from 13.2 to 12.4. If I disconnected the ballast resistor wire, voltage went back up to 13.2. With the Trispark in place (no ballast resistor, of course) the voltage drop when the ignition was turned on was a couple of tenths of a volt.

I had never thought about it before but with the OEM ignition on, you have a ballast resistor constantly drawing power. The ballast resistor get's HOT. That's normal for a points ignition but It takes power to do that. Obviously with a kick start bike and no electrical accessories, a single phase alternator of relatively low power can manage - as they did on Brittbikes (more or less) back in the day. The Japanese used three-phase, larger alternators on their "big bikes" from the beginning. But just turning the headlight on with a stock Norton system is pretty much maxing out the system's capability to keep the battery charged. Put a SHorai battery in there which takes considerably more voltage to be fully charged and there is insufficient power available to keep the battery charged with the stock ignition/charging system.

So I have to say that the choice of the Shorai battery is poor one for a stock Norton ignition and charging system. A lead/acid battery is what should be in there for a standard ignition/charging system since it takes much less voltage to attain full charge. Despite my excellent experience with the Shorai, I'd consider another "test," reverting to a standard batt and again installing the points/AAU but the battery tray area that is made available by the small size of the Shorai is where I have the Alton's starter solenoid and several other components mounted.