Originally Posted by WorkinOnIt
Some Echo machines use those newer "rotary-barrel" carbs. They are a different animal to tune than the butterfly valve diaphragm carbs. Most have NO adjusting screws, but some of them can be enriched from their ridiculously lean condition by removing a plastic cap, pulling out a brass sleeve and inside is the magical High speed jet with a slot in it! You open that baby up a little and it starts much easier, accelerates and runs like a bat.
Thanks, this is an srm-2100, it's 15-20 years old. It has two adjusting screws plus an idle adjustment on it.