I have a 40cc pouland pro with a 18" bar and chain, when I start my cut it is straight for just over half of the cut then it starts to pull to one side what could be the cause of this and how would I correct it?
Most likely the cutters are not sharpened evenly. One side has been filed more than the other.
A worn bar can do it too, also how you hold your hand on the front bar will do if the saw is held off ballance your cut can go astray.
Like was said, uneven sharpening, worn out bar groove or also wrong chain gauge (example: .050 chain on a .058 bar)
Like so many of us we can file or sharpen a chain till it is about 1/2 wore out then they start to pull . I take mine off and run it on the chain grinder to even up the teeth then I'm good till it is wore out . For 2 or 3 dollars have it sharpened and you will be good till it get's bad again or you try to saw a rock .
Does not make much sense but works for me. The few times when that happens to me,I sharpen the chain with the motor on the left side and that will make it cut straight again. I know I can sharpen one side better than the other.
Shortest route to figuring out your problem is to buy a new chain and if it still cuts crooked then have your bar ground or buy a new one. If it cuts straight with the new chain then obviously you have sharpening issues to fix. My experience is that the bar is at fault as much as the chains when this happens.
IME a common cause of this condition is continuing to force a chain that's been dulled on one side, like from rocking it. Cutters on that side then really rub on the guide rail on that side. Don't have to wear things much to make the saw a circle cutter. It's easy to true the bar rails with a bench grinder.
I agree with the previous answers.
Usually when this happens to me it is a worn bar.
I try to get as much out of them as I can.
If it doesn't get flipped regularly and pinched often you will get this walking during the cut.