Well, the bike's having trouble again... vibration while running, feels like detonation on at least one cylinder. Whatever's going on, I hadn't managed to track it down in previous work. I'm also (for now) stuck with the OEM ignition. I'm still waiting on the Ignitech gear.
So, back to testing the ignition - I put a few hours in last night to try to understand what's happening. I got stuck in with an oscilloscope and a strobe gun. I didn't find the problem but did notice a detail, plus got a bit further on how to test this stuff.
Detail: the OEM factory manual doesn't specify wiring colours for the pickup coil leads or polarity in the header. (Time to get the Haynes, I've wanted that manual enough times by now that there's no point in saving money on it any more.) When I connected my borrowed oscilloscope to the pickup connector, it showed clearly that there's a pulse up and a pulse down, or if you swap the pickup leads, it's a pulse down and then a pulse up.
This is important - a look at the stripped CDI confirms that there's at least a couple of transistors leading off the pickup coil connector and a connection on the right hand connector side to ground, through a couple of resistors and capacitors. The transistors will be firing on application of a pulse of correct polarity. The circuit may also be using the gap between the pulses to estimate RPM, although I can't yet be sure of this.
Testing: this has also shown a method of testing an inductive (or variable reluctance) pickup. Connect the oscilloscope to the pickup leads, turn the kill switch to Off, then cold-crank the motor. Inductive pickups don't need anything else running to generate a signal, turn the engine over and you'll get a signal off the pickup regardless. This is about the only way I can think of to check correct gapping / magnet strength / coil function etc without getting inside the engine cases.
Strobe: the gun I purchased is having trouble keeping up with increased RPM. I'm not sure why, yet. What it did show was that neither cylinder is running on the idle timing marks. The vertical is a few degrees early and the horizontal is so early that the timing marks can only be seen at the very base of the timing window.
So... it's a mess. I don't know what's going on or why. About all I can draw from the night's work, and going through the photos again this morning, is that I need to be a lot more methodical in this sort of work. Thrashing around at random isn't going to sort out what's happening.
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