I was cutting a triaxal load of poles My saw locked up. I worked the crank back and fourth by the flywheel it suddenly came free. In restarted it and continued to cut about 6 more chords the job was completed. I decided to take the saw apart to see what happened. The piston circlip came out and appearantly went out the exhaust. I put in two new clips and all is well. The girl has cut much more wood after this happened . It is a Jonsered 2159. Ithink the clip got ground to powder. There is a small gouge at the bottom of the cylinder.