RE: Magnum XLS-52
I have my second Mag .52XLS flying in an old Balsa USA StingRay I use for airborne break-in. I also ordered a 13-4 just to try out. The engine screams with the 12.25x3.75.
The new engine is quiet with an 11-6. I am pretty sure I have ground clearance for the 13-4 and will give it a try this weekend. The old StingRay was climbing vertically, slowly, but vertically, up to 800-1000 feet with the 11-6. It was faster than with the 12.25. For a grungy, draggy old plane it was moving pretty well.
The new one was easier to get running since I pre-adjusted the low end. I remembered the first one had the low end setting so rich the carb flooded full just sitting on my test stand. This time I hooked up a long piece of tubing, closed the carb down to an idle size slit, blew through the tubing and closed the low end down until I just got a small hiss. I think I closed it down a good turn this time. After I did this, I ran it on the bench without needing any low end adjustments for break-in. I did make a couple of tweaks to get it to throttle up cleanly after I had it in the plane out at the field.