I don't understand some of you guys. I thought I answered all of these questions a few days ago after the successful test flights with the Magnum carb. The bore thru the barrel is .388", which is equal to 9.86 mm. This diameter allows for good fuel draw and still makes all the power of the larger carb. The reason is because the fuel/air mixture is now better atomized than with the larger bore. Remember, I saw 9000 rpm on the st carb and 9250 with the magnum on the same prop. The real test, however, is when you hold the model vertically. When the bore is too big, it sags, when it is just right, it holds power or even increases in power. I tried this with the magnum carb and no sleeve, and it ran about like the st carb. Put the sleeve in, and a world of difference.

The other thing I said mine did with the st carb is this. It was hard to richen up. To get it rich enough to then be able to hold vertical, it would be too rich to fly, and would be spitting raw fuel out the muffler. With the smaller carb, I only need to back off 350 rpm from peak to be able to go vertical. The best part is that it only takes about 4 clicks on the needle to get that 350 rpm. On the st carb, it took about 2 turns.

I like the 10% powermaster and the way it runs. The high needle is open 1 3/4 turns for flying. With lower nitro, the needle would be closed a little more, and with higher, open a little more. I think the 10% is fine, but transition may be improved with 15%.