Ok, I have to confess a story which is similar. I bought my first 10-10 for $35 a while back and rebuilt it to be my firewood saw. I ended replacing dang near everything, but when it came time to start it, it was the exact same problems you were having. I had $150 in to this $35 saw along with who knows how much time.
Issues with idling, stalling, and not starting plagued me for months. I finally put it on the shelf and walked away.
Then I stumbled across Leon’s chainsaw repair channel and he had that video about the check valve. So I bit the bullet, took the saw down, took my time, and learned how to replace it. First pull she fired, tuned it, and now she is my go to saw. It’s ported, running 24” bar, and she loves to eat
crazy how one little thing can do that.
so is 3/16 a good size that worked for you? That size is smaller than a 223 casing but larger than a 17 hmr. I’ll have to find one. I think it’s more common of an issue than people think. I’ve had to do 3 out of 13 macs that I have
I’m very thankful to have been able to help and it’s awesome that it worked out. You’re gonna love cutting with that saw.