Describe your sears 18"

Initial settings are one full turn CCW on both low and high side adjustments.

I am confused. Is it a sears saw or a poulan saw? If it is a sears saw you go to sears for the parts. If it is a poulan saw find a shop that repairs chain sawsand take it there. They will be able to find the parts you need possibly in stock.

Should range from 120psi to 150psi

http://sophiesophieshops.ecrater.com/p/6490866/sears-craftsman-owners-manual-23a-23

How old is the unit? Did you leave gas in it for months?

This 'new' 10% ethanol Gas is a Carburetor killer , It is extremely bad for the 'Paper' Fuel pumps that are in the two cycle carbs

I put a new bar and chain on my craftsman 18" chainsaw because the chain keeps coming loose. I am still having the same problem, after running 10 seconds, the chain falls off.

Take the bar off and clean the grove out with something like a small flat blade screwdriver.Make sure its open where it bolts on.It gets its oil through the bolt holes.If you have a way to blow the dirt out it helps.You can try running the saw without the bar on to see if its putting out any oil.If not you will have to get to the oil pump to see if its not bad.

'Oregon' makes very good bars and chains for nearly every saw made. Check their web site for information. Good luck!

Check the fuel filter, air filter, and muffler for plugging. Check the fuel lines for decay or other damage. Make sure the carburetor fasteners are tight. Check for proper chain oiling by running the saw at speed for several moments with the bar tip near some cardboard--it should throw off a thin line of oil. Hope this helps!

If the saw is new, take it back to Sears for warranty repair or replacement. Good luck!