interferencefit wrote:
I guess I meant that I had good spark from the Boyer under a load, as the plugs weren't under compression. What I did was ground two extra plugs to the fins. I fired those plugs and I left the original plugs in the cylinders so that the starter would have to work under compression while the Boyer was sparking. It did spark, and quite nicely, under these conditions. This was done to rule out a weak starter. I'm confident the starter works correctly, as the bike fires up immediately after I hit the button.
Hmmm, I'm not sure what you proved. Perhaps I haven't been following this thread close enough.
But what I'm getting is that you wanted to put the battery and starter under load and you wanted to watch the spark itself in order to evaluate your Boyer in near real life conditions. So, instead of attaching the spark plug leads to the plugs in the heads you attached them to the external plugs so you can get a near real life view of the spark plug's intensity.
There is a fly in the ointment, if I understand what you're doing and why correctly. The fly is that it takes more voltage to arc across the plug electrodes under high pressure than it does at atmospheric pressure. In other words, air under pressure is harder to ionize than air at much less pressure.
Back in the olden days gas stations with garages often had spark plug testers. The pressure was supplied by the gas station's compressed air supply. The question posed to the customer with the suspect plugs was whether his plugs were capable of firing under the high pressure conditions inside the cylinder. The customer would be invited to watch his plug(s) and verify that there was a spark at atmospheric pressure. Then the mechanic would apply pressure to the chamber and invite the customer to watch the plug's performance at elevated pressures, purportedly emulating the conditions inside the cylinder under operating conditions.
Failure of the spark plug to fire under pressure or look weak under pressure would be "proof positive" that the customer needed a new set of plugs.
The actual degree of validity of the tests I couldn't say, but even as a wet behind the ears wise ass teenager I could see the potential for fraud. (Fraud is an ugly word but my brain didn't provide me with a better phrase to use here.)
I do have a test of my own that served me well with two stroke MX bikes when I was suspicious that my ignition wasn't "hot" enough. My Husky 360 MXer ignition got to a point where it just wouldn't run in "battle" conditions. The problem was that the Husky had a flywheel magneto which was terribly expensive. My test consisted of closing the plug gap down to about 10 thousandths gap and see what happened then, since less gap meant that less voltage was required of the ignition system to create a spark in the combustion chamber.
The misfire quit entirely. But of course that didn't mean that narrowing the gap on the plug meant I was now ready to do battle. Two strokes had a nasty habit of fouling their pugs under the best of conditions. And a 10 thousandth gap was much easier to foul than, say, 20 or 25 thousandths.
Possibly the main reason I'm going in to all of the above is to demonstrate how clever I was--then. But the cleverness wasn't devising the above test. Rather the original windings inside the engine case had both primary and secondary windings, one layered over the other. And, of course it was the secondary that broke down--much as it's usually the secondary that breaks down in a conventional coil.
What I did was strip all of the windings off the original flywheel magneto "armature" and I rewound it with a certain number of turns of magnet wire. I'm not sure how I came up with the number of turns to use. Likely I simply wound all the wire on the "pole piece" that it would hold.
Then I installed a conventional coil under the gas tank, made a connection to the coil and, poof! I now had an energy transfer ignition--which worked until I retired the bike.
I almost doubt I could do such a thing now. I would likely get so wrapped around the axle trying to get the various parameters right that I would be frozen. Plus, now, I have enough money to buy a spare flywheel magneto that I would likely do that rather than cowboy up the courage to dive into the project.
Ken
