RE: Tiger .60 . Building suggestions?
With regard to the Magnum .91RFS, I have a new one in an old Joss Stick. It has had a half gallon of 20% oil, break-in fuel run through it on the bench. The fuel is regular Omega with extra castor to bring it up to 20% oil. I used the Saito break-in where you run at 4000 rpm for the first 2 tanks, then lean out for each successive tank. During the bench run, the compression came up very well. As a matter of fact, the compression seems as good as the 2 Saito .91s I have, and they have excellent compression seals. The Mag .91 now has "snappy" compression so you have to hold the plane to turn the engine over. I attribute this to the half gallon of slobbering rich running to let the ring seat well. A proper break-in pays off. I did check and set the valve gap after the bench run.
I installed the Mag in my old Joss Stick, which is my .91-1.20 engine test and run-in plane. I'm running a Master Airscrew 14-6 at this time to see how it flies compared to other engines that have been in the plane(2 Saito .91s, Mag .91XLS, OS 1.08 & .91FX, TT .61). After a few more flights, I'll switch to an APC 14-6 or more probable, an APC 15-4W to get it tuned for fun fly use.
I put only one flight in today because it was cold (below 60 is winter in Florida). I landed and leaned it out twice during a long flight. At the end, it seemed to pull the plane vertical as well as with my Saitos, both of which have been in the Joss. After I leaned it out, I took off and pulled vertical and I remember thinking that this engine is pulling pretty darn good. I'll be out of town next weekend visiting grand kids, but I am anxious to work it out some more, even on the old Joss which weighs nearly 11 pounds. At this point, it would seem to be an excellent alternative to the more expensive Saito. It should also gain a little more power after another gallon runs through it.
As to breakage, I seem to recall from threads here that the Thunder Tiger .91 was the engine that had the valve train problem if you didn't take it apart and Lock-Tite everything back in place. If you do ever have anything break, send it back to Global Services. They are the best I have seen.