Craftsman 18" chain saw 42cc. Starts and runs fine. Will not idle after running for a while. Will not restart when hot. Will start after the saw cools down.

SOURCE: Poulon Wildthing 18" Gas Chain Saw

Some Poulans vent thru a fuel line going from the tank to the carburetor. Some vent thru the cap but eventually the duck bill valve starts leaking fuel. Then I suspect some people change that cap to one without a vent, which causes the problem you are describing.

SOURCE: Homelite 42cc, 18

After it has been used for a while and it won't restart, try loosing the cap to the gas tank and see if there is pressure escaping. The homelites are notorious for the vent screen in the gas tank cap getting dirty and pressuring up which forces more fuel into the carburetor and floods the motor. This is also aided by spilled mixed gas which has oil in it running down onto the cylinder heads and then the sawdust sticks to it over time and building up where it makes it difficult for the cylinder head to get rid of all the heat it makes from running. This in turn makes the gas tank hotter and makes it build up pressure in the tank. If the vent cap cant get rid of it as fast as it is created the increased pressure forces too much gasoline into the carburetor and it floods it out.

SOURCE: have craftsman chain saw, runs ok for a few

The plugged vent gets my vote. Loosen the fuel cap when it starts to starve.

All Poulan IPLs (exploded parts list) are here:
Poulan.com
http://www.ordertree.com/modelinfo/POULAN-WEED-EATER/75.59.html
Find your model, what little fuel system detail there is can be found on it. HTH
Lou

SOURCE: hard to start. once it

Remove the carburetor cover and observe the action of the carburetor throttle arm as you actuate the throttle. If the arm doesn't move, disassemble the throttle trigger assembly (making part placement notes as you do so) and clean out any accumulation of sawdust/dirt. Make sure the cable or rod which connects it to the throttle arm will move--there should be spring return of the throttle arm to idle position. If this fixes the throttle problem, but the kill switch still doesn't work, you may have to remove the left side case to access the ignition module and the kill switch wire which plugs into the end of the module. The switch itself may be full of sawdust as well preventing contact to engine ground. Hope this helps!

SOURCE: I have a craftsman 16" 36cc chain saw. Engine

First thing is make sure chain brake is not engaged is so equipped. Next make sure that chain tensensioner is not to tight to allow chain to rotate. I wouuld remove bar and chain from saw and spray both several times with WD-40 and work chain link by link until they all move freely.Clean and lube guide channel on bar and make sure that bar is not dented or badly rusted.If all else fails replace bar and chain. Good luck and thank you.