Thanks for the reply, I have some clarification and additional info below your quotes
PeterH:
Your timing will be no more accurate than the underlying mechanical sensor, which is likely to be in pretty poor condition if it's as worn as you say. If you're going to go to the trouble of doing this, I'd suggest you look into the possibility of fitting a trigger wheel somehow.
I understand your point here. It was the auto-advancer portion of the points system (bob-weight & springs mechanism) that caused the over-advance issue. I am contemplating imobilizing or removing the advancer and using the points as a TDC input / indicator.
PeterH:
Cars and bikes tend to be electrically quite hostile environments and at a minimum you will need some external filtering and protection on all the inputs; you will also need to be very wary of spikes on the ignition circuit. Even with commercial products designed for the job, I've had problems with electronics resetting due to noise.
Indeed, it is a harsh environment. from what I can tell, the Lenardo is all SMD components, so vibration shouldn't be too much of an issue, especially if its isolated a bit from the frame etc. either potting the Arduino or enclosing it in a sealed box should also address the weather elements.
PeterH:
What you'd end up with is essentially equivalent to a one cylinder megajolt. Have you considered just making one of those, and taking advantage of the existing hardware and software designs?
That was actually one of my initial searches. I already have done a Megasquirt-II v3.0 install on my project car a number of years ago with great results. Unfortunately the only US-based distributor that I found in my search was autosport.com and they wanted $162 +shipping for a megajolt lite jr. v4. With that cost, that's when I started looking into Arduino. For $25, I can get a Lenardo setup and I'd wager no more than $20 more in radio-shack parts plus time, I probably could have something worked up. Even if its only accurate to within 1*, It would still be far superior than the original mechanical advancer.
PeterH:
If you're anywhere near burning holes in pistons and it's an engine you care about (and assuming it's basically sound) then you really ought to be looking at monitoring and controlling the air/fuel ratio in conjunction with the ignition, and monitoring for knock.Your other option is to remanufacture the existing mechanical dizzy, which would probably be a much quicker and cheaper (and safer) option and would make sense if it's just an old engine that you want to keep running without doing any further damage.
Those are valid points on knock and AFR. I should have been fine on the fuelling (rebuilt the carbs with bigger jets etc), leaving pretty much an ignition issue at that point.
Unfortunately R&Ring the original advancer system, while cheaper than a MJLJ setup, would be around twice the cost of the Arduino setup I am considering and less functional as well.