Stihl 038av chainsaw

Presumably piston / cylinder worn. A rough test is if the saw can be dangled by it's starting cord without turning over. 038 pistons and cylinders are available on ebay, both copies and originals. I fitted a replica to my 038 and it's been a great transformation - seller called blindstickinsect iirc. Change the flexy pipe from the crank case to carb - it pumps the fuel - they perish.

Andfrew

I would still expect to feel some cyclic resistance if the crankshaft is turning. I think it is more likely that something has gone wrong with the ratchet / freewheel part of the starting cord system. These are normally fairly easy to service because cords do break, but you need to be aware that you might well release the return spring. (Not normally as difficult to get back together a steel rule).

You could also remove the spark plug, if the crank is turning you should hear the puffing and you could also check visually or by putting a stick down the hole.

. Thanks for all your replies, the saw is now working. I took the pull cord p anel off and manipulated the ratchet arm. Something clicked and the stud on the side of the arm moved into another part of an R shaped piece of wire. I reassembled the saw and it the turned over as expected.