Ok guys I can't decide which engine to use, I have a saito 72 and an os 55ax. I am going to put it on a green rc edge 540 with 55 inch wingspan and 680 inches of wing area should finish around 5 pounds. I will be flying 3d with this plane and when you advise which engine you think i should use suggest a prop by size and manufacturer please.

I would use the Saito with an APC 14x4w prop. It makes a great 3D combo.

-Matt

Oh I guess I should also mention that the engine will by mounted inverted and I have heard horror stories about inverted saito's. Any thoughts?

I have 3 Saitos, including a 72. It runs like a charm all the time and it's inverted. Same goes for the 91. I have a 56 but it's upright. I love all of them. They start very easily, are very reliable, and they pull like an ox. Plus, they sound cool. Go with the four stroke.

I agree with the 14x4 prop for 3D. A 13x6 will work well too.

The saito 72 it is then and I already have an apc 14x4 wide prop for it as well. I will post how I like it when it is finished and flying. Thanks for the help.

Adicted:

Usually when a guy gripes about not being able to get a inverted engine to run correctly, need to examine the speaker. Does he always twist on the needle each flight of the day? Are all his engines mounted upright or to the side? Usually this breed of cat is #1, tone deaf, #2 would not recognize a fat or lean condition, or a plug getting ready to die from age? Their engines never, never,never are up to snuff because their learning curve is flat lilne. Idts funny to have a guy cry, get good help and get the engine running correctly, dud flys it one time, very happy with it and then starts to twist the needle the next flight. Go figure!

OK being extra cautious I mounted the saito inverted on a stand now when i got this engine it was used and i had problems with it (mounted sideways) but tracked the problems down one by one first the valve lash was out of tolerance two o-rings were bad and the brand new fuel tank it was feeding from was bad (nitro models grrrrr never again). But now it will be mounted on a powerline edge 540, first test on the stand amazed me, idle was perfect no adjustment to fuel started easily and ran great maybe inverted is the answer either way I have a renewed faith in this engine and again thanks all for the help.



Jeff

This may be moot by now, but I think if you want true 3D performance out of a 5 pound bird, the .72 might not be quite enough. If it were me, I'd probably go with the .55.....but that's just my opinion.

E