Tom here's my 2 cents. Your temps are not to high, but your plug reading is indicating a lean condition and/or a hot run in the air. Not to be argumentative bubbagates. I have in flight temp'd a few engines and they will hit 300+ when running hard. Tom, I assume you took these temps after landing and that number is just a "best guesstimate" number, but you sound in the ball park anyway.

Be sure and check your fuel system all the way from the clunk to the carb and make sure there are no leaks, etc. Make sure there are no air leaks in and around the carb spacer too. Next I would go to you local saw/lawn mover shop and buy a rebuild kit for the number on the side of the carb. Take your time if you have never done this before and do one side of the carb at a time noting where which way and where all the parts came off.

Edit--Just read that you found a blockage in the screen, that might be your problem and I would try and run it before rebuilding the carb. I always filter from my fuel jug with a small in-line automotive paper filler and don't seem to run into problems with crud in the screen.