I have a royal airplane engine and I cant seem to figure out what size it is. There is no size stamped on it. Only a royal sticker on the left side of the engine. I have another royal engine which has a 45 stamped on the side. This engine seems a bit larger than the .45. Should be within the 45 to 50's range but dont really know. Anyone know enough about these things to tell what size they are?

Royals were made for several years by at least three different manufacturers. All the ones I've seen were either 45's or 46's. That's not to say there were not other sizes though?

If the Royal logo is really a glue on sticky the engine is probably a Leo .46 also sold as Megatech, Mecoa, and Leo.........RJ

I have a Royal 40 and 45 but have not seen a Royal 46.

You might want to measure the bore and let us know the diameter.

Bill

The Royal .40 and .45 had a two piece front housing like the OS FSR's they copied. Later, the .46 went to a one piece case like the OS SF .46. I am not sure if the .40 was offered with a one piece case or not. Royal did offer a .28 at one time. There may have been a few other displacements, But I have had a .40 and .45 two piece case in my hands.

They were decent engines, but the metal was very brittle and didn't survive crashes well. There was a throttle stop screw that was too soft and caused problems. I replaced mine with an OS part and never had any problems.

turbo

Yes the metal is brittle and almost all Royal engines have broken engine or muffler lugs. There were at least three types of carburetors and carburetor parts are often not interchangeable.

Bill