Why Sthil chain saw loses power when cutting?

Sthil?? Chinese cr*p; or Stihl?

This problem can occur on any type of chainsaw (Husqvarna, Dolmar, Solo etc.) and not only on Stihl.

There could be several problems.

1) Maybe the clutch is worn out or even broken

2) Piston rings might be worn out

3) Piston and cylinder might be worn out (these two are very expensive)

4) Fuel filter and fuel lines as well as fuel vent (if there is such on your type of chainsaw) might be clogged

5) Air filter might be clogged

6) Ignition coil might be faulty...

I had a similar problem on my Stihl 041 AV. I replaced the clutch (took the good clutch from 031 AV and installed it on 041 AV - it fits and works great, btw :D) and piston rings.