GMS engines are warranted and serviced by Hobby Services just like O.S. Max, Tower Hobbies, and Super Tigre. I had a GMS .47 that I ran too lean when the head gasket was leaking, and the crankshaft broke. I mailed it off to Hobby Services along with my receipt and had a brand new replacement engine in my hand exactly one week later.

Magnum engines are serviced by Global Hobby, and Global also has an excellent reputation. I've never had to send any of my Magnum engines in for service, so I can only comment on the good things I've read about Magnum engine support here on the forums.

Another line of engines that are not always at the forefront of many modellers' minds are the Super Kraft (SK) and JBA engine lines sold and serviced by http://www.kangkeusa.com These engine lines offer very good performance and value, and the folks at KangkeUSA likewise have a good reputation for service, support, and parts availability.

After having said all of that, I recently bought a Super Tigre G-61 ringed 2-stroke for my King Kobra. It was on sale at Tower Hobbies for $79.99 ($5 off), and I'm awestruck at the power, performance, and ease of break-in and tuning this engine offers. When you throw in a 3-year warranty backed by Hobby Services, I really have a hard time guessing why more folks aren't flying Super Tigres.