Managed to get the screw out with a drill set, replaced it, took out a head shim. P/S seems still to be in good shape and has more compression now witht he removed shim, and fires up quicker- but I also added an EFRA 9886 pipe too. The $18 is still paying off!

Not sure how much fuel has been run through this motor but when I got it, I've done maybe 1/4 gallon so far.