Ty, a 92908 (i.e. basically the same engine with a PulsaJet instead of a VacuJet) from the same period was likely to have a carburetor made from Minion plastic, it wasn't only the VacuJet.

On the introduction of the Magnetron breakerless ignition, note that there is an official B&S way to retrofit these to breaker-point engines:
http://www4.briggsandstratton.com/miscpdfs/RNT/magnetron_retro-fit.pdf
Joe Carroll's way seems quicker and easier.

I have only found vague references to the changeover date to Magnetron on the internet. Some say 1982, some say it was mostly done by 1983, and some say it happened progressively over quite a few years (this last assertion might have been referring to changing the large industrial models to breakerless ignition, I think). I fully expected to see a Magnetron coil on the 92508 in the pictures - I've never needed to take the cowl off it before today. This diagram shows where the Magnetron module should be visible (the coil installs with it underneath, toward the engine, not on top, where it would be easy to see):
[Linked Image]
In the third picture in my previous post you would be able to see it up near the air vane, on the opposite side of the coil from the HT lead. And I agree, that was the object you circled in red on sparker's coil: it appears to be a standard Magnetron, just like in 1983. Maybe I should get my glasses replaced.