I have a Magnum .60 in my biplane. I ahve had it for a while and ti is already broken in. The problem is that the engine does not hold a very good idle and it quits when i full throttle it quikly. Then after i run it for a while the idle is to high and it wont stop. I have tuned the needle valve right and everything but i still cant figure out why it is doing this.

Sounds like your low-end mixture is too rich.

This is just me, but I would put a new glow plug in it, too. And with any fuel mixture issue, I make sure the carb and fuel are absolutely clean. It's sort of like re-booting Windows-sometimes you really have to, and at worst, it doesn't hurt. Then ever so slowly lean the idle needle (a tiny bit at a time!) until you get a good idle and transition. Sounds right, though-bottom end is too rich and it's loading up with fuel at idle.