It may not be the glow plug. We run all two-stroke engines with O.S. #8 or #A3 plugs. Never had a problem caused by a good OS plug.

With the GMS .47, you don't say what prop and RPM. We normally prop them so that they'll turn in the hgih 12,000's when leaned to just rich of peak RPM on the ground.

If your engine won't accelerate past 1/2 throttle, we'd suspect that the idle mixture is much too lean. Richen it a LOT, on both idle and high-speed needles, start the engine at part throttle, and then open the throttle to full. Lean the high-speed needle at least to the point where the engine stops breaking back and forth between two- and four-cycle type running. If the engine will take the needle, go ahead and lean to just rich of peak RPM. Now you can adjust the idle mixtures. When you accelerate to full, you may have to keep the glow plug battery attached if the mixture's extremely rich.

We've found that, many times, the modeler tries to adjust the idle mixture first. This is a no-no because you can wind up with the idle needle interfering with high-speed fuel flow. On most model carbs, you need to start out with a rich low-end, adjust the high-end, and then get the low end adjusted.

Use a 10%-15% nitro fuel with at least 18% oil content and containing castor oil as part of the oil package.

Also, many people try to idle too slowly. Accept a few hundred more RPM so that you can get good acceleration. Anything below 2,400 RPM would be considered good. Even if you can get it lower, it may be at the sacrifice of good acceleration.