ORIGINAL: spiral_72
Well I pulled the carb completely apart. It's pretty simple actually. I knew as soon as I had all the pieces laid out that dirt/sludge/dried oil was not the problem, but I washed everything in my parts washer anyway. I blew all pieces out and noted any passages taking special care to make sure they were unobstructed and undamaged.
I have to start it yet. Why does it rain on every weekend that I have some flying time?
I'll keep ya posted.
Spiral
I have gone through all the problems you are having with a second hand Magnum 40 that I bought from a club member. It was a two year old engine. When I flew it on a new trainer it was surging in flight so I would tune it for optimum performance before flying and it would run good for 2 flights then sputter, surge, and sometimes die. Tried most all things you did while I had to wait for the O-RINGS I had ordered for the low and high speed needles. I had suspected this early on but the o-rings were backordered for some time. Once they came in and were installed the problems went away and the Magnum ran like a new toy. Still running it a year later. Hope this helps you.
Steve