I have a brand new gms 32 and have been running it in with a few tanks of fuel....the problem i have run into is that the engine won't run below 5,600rpms. Can anyone offer a suggestion as to why or what to do..... is it possible that the fuel tank position is effecting the idle speed? I have tried the engine mounted on the airplane in a sideways and an upside-down position; both with the same result

thanks,
chris

Be sure that your throttle is operating correctly, and that it closes completely when the throttle is lowered. That'd be the first place I'd look.

It's a new engine as well. New engines, particularly small displacement engines aren't known for their "tick-over" idles, and tend to idle at faster speeds (albeit lower than 5600). 2500-3000 rpm should be more than acceptable for a small engine.

Prop size would also influence your idling speed somewhat. I'm guessing you should be running a 9-6 (or so) prop. Smaller props tend not to allow as low an idle speed as do larger ones.

In the end, the "best" idle speed is one that permits reliable acceleration, and doesn't cause the airplane to be difficult to land, or have the model rolling around the pits at idle.

I have 4 of the little buggers and a buddy has 2, all started out on twins.

First, we couldn't get them to run reliably when new on a small prop. We settled on a 10-6 to keep the rpm down. With 9-6s, we had loads of in-flight engine failures and I had one run really bad and another throw a rod bushing, trashing the engine. Both were replaced under warranty.

Second, they seem to need nearly a gallon of fuel before they are run in enough to really get the idle adjusted. I finally put one of mine on a Little Stick and have been flying acro with it. It now starts in 1 flip and idles beautifully.

I would say the Chinese engines don't have the close tolerances so they tend to make them tight. This requires a longer break-in than OS, for exampple. I also noticed my GMS .47s were the same. I would recommend a 10-6 prop and more running time. Mine came around. I'm pretty sure yours will, too.

I use 10% Omega castor blend fuel.

the prop is a a 9X6 and the carbrator is almost completely closed when at 5,600 rpm. The breaking-in was done with a 8X6 and the idle was at 6,000rpm

How much is "almost"? Bottom line is that the engine is getting air from someplace. The knock-off engines are notorious for air leaks, and a likely spot for this to occur is at the base of the carburetor where it mounts to the crankcase.

Loosen the cinch-bolt securing the carb, and with your thumb over the air intake...press down FIRMLY on the carb body to fully seat the carb on the crankcase, and compress the O-ring. The O-ring is installed right?

While holding the carb securely pressed down, re-tighten the cinch bolt, and then give it another whirl.