I just broke in and flew a new Magnum XLS .46A on a Phoenix Dolphin ARF yesterday. It was a terrific out-of-the-box experience and the engine fired up easily the very first time, was spinning a 10x8 APC prop at 12,200 rpms on the very first break-in tank, and was idling reliably right out of the box. I put 3 flights on it after a single break-in tank on the ground and the engine performed flawlessly.

I've had very good experiences with Super Tigre engines as well, and I wouldn't hesitate to buy a GS-45 ABC either. As powerful, reliable, and easy to tune as my Super Tigre engines have been, I'm surprised that a lot more pilots aren't flying these at my clubs.

My GMS .47 took a little while to break in, but was very powerful and reliable after the first six tanks or so. My GMS engine had a tendancy for cylinder head bolts to work loose after a while. In my experience, GMS engines require a little more dilligence with regard to maintenence; I'd buy another one for the right project, but I'd be careful to check it regularly for loose cylinder head or backplate bolts.

I haven't had the opportunity to try an Aviastar engine yet, but they are strong runners and reliable by most all reports. Folks who received engines with faulty carburetors report quick service from Sig with regard to getting things sorted out. The machining and overall parts quality is reported to be excellent.

It's really amazing the quality and value of engines that are available in the $49 to $79 price range these days.