Nice detective work. It is a Tillotson HS-179B. I don't have any specs on the carb, but I do have a rebuild kit for it. Tillotson was a Borg Warner company back then. The engine is a Homelite 54.2cc, quit a monster. The book says it also was fitted with an "equivalent" Walbro SDC62. That has a WHOPPING 14.25mm venturi.

I actually stumbled on the fact the Homelite XL12 chainsaw has both a loyal vintage following, and it also has a cult following. The XL12 stands for a 12lb head, the lightest available in 1964 when it came out. People are inheriting these things for two generations straight with incredible loyalty. They were the first truly lightweight magnesium alloy chainsaw in the world. I know, when doing this conversion I started a small bright fire at the base of my belt sander when a spark lit the debris pile. OK, that's the loyalty part; here's the cult part.

The Homelite XL12 was prominently featured in the movie poster for the Texas Chainsaw Massacre. Here's a copy of it, where it even SAYS XL12!

Dogshome, I now recognize your pneumatic diagram from my long thread "Saito glo to gas conversion". I think your setup works because the intake part of it only happens every other revolution, but you're getting a +/- pair of pulses every revolution on the crankcase part of it. Now, the question is how much pulse pressure is robbed by the intake part when the intake valve is closed, and how much robbed when it's open too? Remember, that line is open all the way from the pump diaphragm cavity all the way out to ambient thru the carb venturi. Yes, it's a long path usually, except on that ASP where the carb is direct-mounted to the head. A precise low pressure gauge would be interesting to use here, as a test. My guess is most of the pulse is from crankcase, with some parasitic happening from the intake part of it. But latency from the small diameter tubing is allowing it all to work. In other words, the dominant pulse comes from the crankcase, and the diaphragm reacts before the pulse can "escape" out the intake. And it's enough to scavenge the oil coming from the crankcase.