Mesaflyer, I think it would depend on the engine and the way it's mounted. I've had my O.S.52 mounted in three different planes, One was upright, on was on it's side, and now it is semi inverted, the head pointd down at 4:30 looking from the cockpit. The O.S 52, as well as some of their other carbs has the high speed and the mix on the same side of the carb. That made it easy to make both adjustments while the engine was running, in both the upright and side mount. The semi inverted is a different animial. You have to make the adjustments from under the plane, so in that case there is no way to make a mix control adjustment when the engine is running. My Magnum 4 strokes have the mix opposite the high speed. With them, if they are upright, you can make the adjustment running, but if it is side mounted, you have to kill the enging between clicks.

One other thing, I have what we used to call a Selectric screwdriver. It was made for working on the old Selectric typewriters. It has a fine tip, that fits the mix control perfectly. It has a shank about 10" long which puts the handle well outside the arc of the prop for anything I fly. Even with that, it is extreamly important that you never get your hand or the screwdriver near the rotating prop. Always stand behind the engine, never reach over the front.

I had this last point driven home the other day when I was tuning up a little Mag 40 GP two stroke. It was part of a collection of stuff I bought a couple years back and it was the first time I had started it. It started right up but when it went full throttle, it ran well for a couple seconds then started slugging down. I was thinking it was running rich, so I clicked it lean a couple clidks and ran it up again. At full RPM, id stopped, spitting prop and spinner. They both flew into the back of my garage and when they bounced away from the wall one went left and the other right. Had I been standing any where near the front of the plane then, one or both would have hit me. Four strokes are more prone to spitting a prob, but even the little Mag 40 showed me it could. Stay to the rear, and if you can't shut down the engine for each adjustment. Never stand in front when running up an engine, or let other people stand in front. Scares me to death watching a guy with a big 1/4 scale reaching over the prop to give the needle a couple clicks. Even the little ones can bite you. I've got a scar on the second knuckle of my right thumb from sticking it into the prop of a little .049 when I was about 14, some 50 years back. It cut it to the bone. Be safe.

Don