I had very much the same issues with an older BME44 and cleaned the screen, replaced the plug and ran a bunch of carb cleaner down the carb and removed the needles and shot it down there too. It ran like a different engine! I started over with the needles and in a few minutes it was kickin As$ again. I wished I had a diaphram to replace the old one as they are cheap but I don't know where to get them. I hope you get that brison up to snuff soon. There is someone at my field that has one and it is a very strong engine.

HTH

Joe