Hey guys, Im looking to be putting together a sig four star .40 soon. This will be my first build, now im new to the hobbie and dont understand all of the engine specs, I do know sizees for certain planes but dont know the differance between two engines that are the same size that end with differant letters. Allso the four star directions call for a .30, or a .40 engine, now can you install a bigger engine on this plane like a .46 or so?

Sure, most any 2-stroke engine in the .32 to .46 size (or larger) will fly the Four Star .40

Most manufacurers that offer two engines of very similar sizes will make a plain-bearing and a ball-bearing version. Plain bearing engines aren't quite as powerful as ball-bearing engines, but they tend to be lighter weight and don't require as much maintenence (no ball-bearings to rust).

The O.S. .46 LA is plain-bearing, for example, while the .46 AX is ball-bearing. The Thunder Tiger GP-42 is plain bearing, while the Thunder Tiger Pro .40 and Pro .46 are ball-bearing engines. Some companies like Super Tigre, Magnum, Evolution, and GMS only offer ball-bearing engines.

Ball bearing engines are a little more flexible with fuel requirements than plain bearing engines. Plain bearing engines run best and last longest when run with fuel that contains mostly Castor Oil for lubrication. Ball Bearing engines will run well and last a long time with either synthetic or castor oil lubrication. Most airplane fuel contains a blend of both kinds of lubrication, though, so don't worry about this too much.

Plain bearing engines are easy to tune and very reliable, they will last a long time. Ball bearing engines are usually more powerful even though they're a bit heavier. Either kind will work well on your Four Star so long as you read the owner's manual, break it in according to the instructions, and feed it the kind of fuel recommended by the manufacturer.

Good luck and good shopping!

Yes, one of the currently available 46 engines would be ideal

Thanks guys that cleared up alot of confusion I was haveing. once again thanks.

One more fact:
4 stroke engines run bigger for the same application as 2 stroke.
For a 40 to 50 size 2 stroke you would use a 50 to 70 4 stroke.
60 size 2 stroke you want an 80 to 90 4 stroke.
a 4 stroke for the 40 size 4*? OS or Magnum 52, Saito 56 would fly it fine, Saito 62 for more authority. There are many more options but I just wanted to give you an idea of what you can do.

Well I have to ask .... do you already know how to fly RC airplanes ?
If not please find a club near you and ask for an instructor to help you.
The Four Star is usually considered a second or third plane, but depending on how old you are and the instructors willingness you can learn to fly using the Four Star.
Oh yeah the older you are the harder it is to learn how to fly.

AMA club locator http://www.modelaircraft.org/clubsearch.aspx