Time to bust out the old sonicator – a 1960s Narda SonBlaster 600 that my dad trashpicked about 35 years ago. It’s still going 60W strong. One of the cooler features is a limited tuning function that allows you to max the coupling constant for a given group of parts. It has two tanks and will drive one at a time.
The carb parts cleaned up very nicely in a 40/60 mix of Simple Green and water.
Although I ordered up some new jets for it, I likely won’t use them. The OE ones are in good shape, and I’d rather re-jet for a slightly richer mix.
The culprit was the air filter – it had a bad day. As far as I can tell, the mess is limited to the intake horn and the carb. I’ll get out the boroscope to check the intake valves tonight. And try to find a new air filter. A paper one would be better, I hate foam filters for exactly this reason.