I'm feeling like I made negative progress today. I was going to swap out the rollers but the rollers in the known good engine were unevenly worn.
The six of them weighed 77g or approximately 12.8g each.
I didn't want to put the unevenly worn rollers in the engine I'm working on so I put some 11g sliders in that I ordered a while back. The rollers I pulled out weighed exactly the same as the the known good engine. 77g for the six.
I loosened the carb and reset it as it looked like the rubber boot wasn't perfectly straight. I also put the clutch assembly from the known good engine into the one I'm tinkering with. Also swapped back to the original exhaust.
I didn't get to do a plug test due to time constraints but I did get a significantly higher speed than I've been getting. Average in the straight was 33mph. Weird.
I'm not sure if it was the clutch, sliders, or me finangling with the carb. Sigh.