I was daft enough to lend my chainsaw to a "friend" who brought it back unable to cut straight, in fact it cuts hardly at all before it jams . My saw is a PRO 40cm electric PRO2100CSA
They are available from your local hardware store or B&Q or online.
Richard
March 2011
It is almost cetainly just a problem of blunt cutting teeth- you need to find an appropriate sized round file and resharpen; the guide bar is probably fine unless it is showing signs of damage on the rails or around the sprocket, The cutting teeth are almost certainly more blunt on one side than the other causing a curved or twisted cut which will lead to a jam.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix gardening.