What causes smoke from a chainsaw muffler and how do I fix it?

Smoke from the muffler is usually a rich fuel mix or a clogged muffler screen. Check your fuel mixture first — for a chainsaw that’s typically 50:1, but verify your manual. If the smoke is white/blue, it’s burning oil; if dark black, it’s a rich mix or restricted exhaust. Pull the muffler off and clean the spark arrestor screen with a wire brush or replace it. If that’s fine, dump the gas and mix a fresh batch at the correct ratio. Also check for bar oil leaks onto the muffler, which can mimic combustion smoke.