I own 2 craftman chainsaws, the first one cylindar & piston,burned out. I found out from forums that this was a common problem with sears chain saws.
Here is a quote about the problem "Air leaks cause the mixture to become too lean fuel wise,which causes overspeeding, and the fuel mix also helps cool things, as well as being the only source of lubrication, all of these factors make this extremely critical in the life of any 2 cycle engine. Sears would not fix the problem because my chainsaw was out of warrenty by 2 months. On my other saw the chain bar adjustment gear cracked, so that tention on the chain will not hold.
The thinkness of the medal of the adjestment gears is less that 1/8 inch thick:which is much too thin. Sears would not replace the the Chain Bar it was out of warrenty