Hey-
Listen, I did some research on this today. Guess what? It seems that the government has mandated that carburetors on 2-stroke engines be made
difficult to adjust.
This has been accomplished by shaping the adjustments specifically, so that the average consumer cannot "molest" them. They require a special tool. There are several- one called a "spline", a "D", a "double D", and then there is the one that I've described.....the "Pac-man" tool.
Here's a link to a forum:
Handyman WIRE - Handyman USA : Homelite 42cc Chainsaw Tuning
If you go online, it is relatively easy to purchase this tool. I found one one eBay for $18. So much for that little problem! I know what I'm doing when I get home next week...
Good luck!
N