What size spark plug for poulan 42cc chain saw?

SOURCE: 18"poulan chainsaw

Start at 1.5 CCW form lightly seated then tune for performance like this:
Carburetor Adjustment by Madsens.com
http://www.madsens1.com/saw%20carb%20tune.htm
CW is leaner; to lean will destroy the saw. If over tightened closed (CW) the adjustment screw faces are easily marred; marred adjustments are difficult to impossible to set properly.
Clean the air filter; adjusting with a dirty filter can cause a run lean condition once cleaned and the saw run.
There are 2 wav (sound - idle & full – may not be highlighted) files that I find most helpful, I think you will too.

I think your starting procedure may be the cause of flooding. Flooded is the #1 cause of hard starts in 2-cycle engines. Read carefully the recommended start in your manual. most miss the second note. It should be similar to this (read 3, read it again):
Warm start in the manual says 1/2 choke BS. Close choke, (sets fast idle) open choke, pull rope.
Start Procedure
Cold:

1. Ignition on/off to on
2. Set compression release – optional step even if saw is equipped with a compression release
3. Pull (close) choke, set fast idle (done when choke closed on some saws); pull starter and listen for an attempt to start. once heard (usually two pulls; no more than 4).
4. Set compression release – optional step even if saw is equipped with a compression release.
5. Push (open) choke pull starter until it starts (usually first pull).

1. Ignition on/off to on
2. Set compression release – optional step even if saw is equipped with a compression release
3. Pull (close) choke, set fast idle (done when choke closed on some saws) – Do not pull with choke closed.
4. Push (open) choke, pull starter until it starts (usually first pull).

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SOURCE: My poulan chain saw will not start 42cc 14

K, I just looked at their site for another reason but they indicate that you need to make sure of the fuel, the on/off switch and also the spark plug (which I have personally seen) and dirty or clogged fuel lines. If you need to view the manual for the troubleshooting you can go to Poulanpro.com or call 1-800-554-6723. Good luck and let me know if you need more help

SOURCE: chain sprocket

I looked at a breakdown for the 42CC not sure if the same one or not but it appears that the chain sprocket is held on by an Eclip and behind that a flat washer. If this doesn't look like yours give me the model number and I will research another breakdown

SOURCE: Poulan Pro 42cc Just Won't Cut It

The chain is directional, only cuts one way. If a new chain won't cut, it must be on backwards.

SOURCE: my poulan pro 42cc will not start i get sparks

If you have spark and compression it must not be getting fuel.
Put a little mix directly into the carburetor and try to start it. If it pops and doesn't continue to run look at your fuel lines. I think you have a cracked hose. HTH
Lou