661 breaking piston skirts

[timbertramp]

Has anyone seen this much? I’ve had this happen twice on one saw and just had another saw do it. The first saw I took out the intake “flange” inside the case and it hasn’t happened again. This last one there was a faint mark on the flange but could have been from the broken piece. There was some scuffing on the bottom side in the intake port, looked like maybe from piston rock however there was no ding or anything where the skirt hung and broke.

I’m baffled.

 

[Cobby08]

That looks really coked up or is it just the picture?

 

[pro94lt]

High use saw?

 

[timbertramp]

One saw had a year on it and let loose, new piston and let loose again in three hours. Put a whole new top end on and removed the internal flange and been running since (as a back up saw).
This saw had about a month on it.

Shed is dark probably more the pic

 

[Chainsaw Jim]

Is there something else to the story like maybe there was a log or something heavy on the saw at some point before the first failure?

 

[usmcbuckwild]

I’ve been given two different 251s to work on with the exact same issue: bottom of the piston skirt broke off next to the intake port. I did the same thing; smooth the lower edge of the intake port and I also smoothed the lower edge of the skirt on the new pistons. Both saws were less than a year old. So far no issues.