ORIGINAL: WarpedWing
I asked the same question on the SPA Bulletin Board and Bruce Underwood told me that 4 strokes were favored because of reliabity and torque (prop selection). With respect to the OS, he felt the OS broke in easier, was less fussy to adjust (and keep adjusted), and requred much less maintenance. I'm building a Sun Fli III right now, and I'm putting an OS 91FS in it. I'm hopeful of attending a few SPA events this year. Regards,..WarpedWing.
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Generally, engines that produce less power are in a lower state of tune and are not as fussy on adjustments. For those wishing to have fun, but are not four-stroke experts, I can see the appeal of an OS .91 Surpass II and the Magnum .91 clone of same.
The Saito break-in isn't all that difficult. Just time consuming. I've seen folks pop them onto a plane and just set them up rich and broke them in that way without horrible consequences. I think that is a non issue. At least it is to me.
I like OS engines, but the Saito .91s is so light and small that it just begs to be used in this application. I also suspect that the Saito .91 utilizes nitro a bit better.
After saying all of that, I have two Saito .82s NIB, so I'm going to substitute an .82 for a .91 and see how well it handles the models. If worse comes to worse, I can put the .82 in the Kaos 40 ARF and be powered more than adequately, especially when running higher nitro fuel.
I'm not giving up on the Rossi .60 and Ultrathrust combo, however. There's too many great choices in this hobby. Know what ah mean, Vern?
