The new (and correct B7HS) spark plug helped it start more quickly, its tiny Encarwi carburetor has been cleaned, etc., and I've fooled with the float level. Each improved matters slightly, but on every test run, somewhere on our test hill, it cuts out without warning. It'll start once more without waiting.
I've paid very little attention to the ignition timing, and the float level still might not be correct (though in the past it wasn't a problem.) The bike ran well when I first got it, but I'm wondering if something horrid, like shaft seals, perhaps have finally given up.
So: is there a way to check crankshaft seals? Should I guess again at the float level (the diagram I initially used made no sense and might have been for a different model of carburetor)? Would ignition timing be the culprit? A capacitor (condenser) perhaps? (It tested okay with the ohmmeter, but I don't trust them.) There just isn't much inside this here mobile chain saw.
Thanks for any advice.