I use an APC 13x6 on my Super Tiger .75, and other guys around here use that prop with good results, I don't think that's your problem.

As others have said, it's rather hard to diagnose an engine over the web.

However, there are lots of threads on here about setting the mixture, using a pinch test to check the mixture and so on. If you dig around, you're sure to find one, there's lots of good info.

I'm guessing you have the mixture too rich on low end, or you are trying to idle too slowly.

If you get the engine running, and run it up to full power, then down to idle. Wait a second, then apply power, does it kill instantly, or does it burble and accelerate or die? Is there liquid fuel coming out of the exhaust at idle? Can it idle for just a second or two, but can't idle longer?