I have run the engine in as recommended by David Gierke in his article in Model Airplane News and have used almost a quart of fuel. The engine starts easily and idles reliably in the hanger but cuts as soon as you bring the throttle back to idle at the end of a 100ft takeoff run, during ground handling trials on a new plane. With the glow starter connected it idles perfectly. Given that I am flying at 7000ft would it help to switch to a hotter plug (currently using an OS #3), higher nitromethane (currently using 10% TowerPower). During ground handling I leaned it as far as it would go before the rpm dropped to try and keep it hot.

Advice please.

At high field elevations, it would be difficult to get the carburetor balanced between high and low RPM mixture settings. The air's too thin to get a good 'set' on the low end once the needle's correctly-set for top-end. The idle is too rich...to get a good idle, you have to lean it so much that your midrange goes out the window.

You may wish to try a hotter fuel. The added nitro is an oxidizer, so it adds power by allowing more fuel to be burned. This may help your transition problem. The only other solution is to accept a higher idle RPM and prop the engine so that you can slow the model down enough to land.

Thank you. What prop would you recommend to slow the plane down at high rpm? What is more important diameter or pitch? I ran the engine in with a 10x6 and was planning on flying with a 11x6, 11x7, 11x8.

You may wish to try a 10 x 7 prop, or even the 11 x 6. See how it performs. If the RPM isn't between 12,000 and 13,000, you may need to bring the diameter down a bit.