Newbie at field has one in his trainer, a few friends and myself, all experienced modelers spent a frustrating afternoon trying to get it to run well, , most things were tried, we changed the plug, changed the prop, took off the restrictors on the needles in case that was the problem but nothing worked, it would start and pick up fine until mid throttle then just lean out and die. After about three hours of fiddling we abandoned it, one of the guys, who works for a model fuel company took it to his workshop and eventually found that the baffle in the muffler had a really small notch to allow the gases to pass into the second chamber, once this was opened out to a similar size to the tailpipe internal bore the problem was solved. I gave the newbie three flights last weekend, engine starts and runs well, no flameouts and seems to produce average power for a 46.