Tim, your little engine runs just as sweet and regular as one could ask...wow! I have made a note of your O ring source so I can follow your lead should mine develop problems.
Can you tell me what fuel you are using and what lubricant...then fuel/lube ratio. I keep experimenting, and currently using 15 parts Zippo to 1 part Marvel Mystery Oil...runs well, but always open to other's learnings as the "manual" is pretty scant on these.
Rog