Sorry I'm late to the party. I had an Evo 46 NT that came in my Hangar 9 PNP Cub. This turned out to be the worst engine I have ever owned. It was supposed to be pre- set from the factory with no break in required. From the moment I first turned the crankshaft the bearings felt kind of "gritty" if you will. I contacted Horizon and the tech guy said this was normal. I thought this was kind of weird but o.k. I'll try it. I ran about a half a tank of fuel before it's maiden flight just to check things over. Maiden flight lasted about 45 seconds before silence and a deadstick landing of an unfamiliar plane. Reset the needles and tried again. This flight lasted about 1 minute before a wheel fell off and cut the flight short. I packed up and went home. The next time out seemed o.k. on the ground after running a full tank of fuel through it. Took off and about 20 seconds into the flight it quit again. Another deadstick and more aggravation. I took the engine out of the plane and mounted it on a test stand and still the same problem. Idles o.k., accelerates o.k. and then all of a sudden it quits. No sputtering, nothing. I tried different glow plugs and different fuel, removed the limiters, swapped needle valves with an old Magnum GPA which were a direct fit, tried different o-rings on the needles checked the o-ring under the carb but still the same result. I contacted tech support and they said it might be bad bearings so I sent it in for warranty repairs. Guess what? They said they replaced the bearings and still couldn't get it to run right and now they are sending me a new engine. I don't know if it will be the NT though as it looks like they replaced it with the NX but whatever they replace it with I'll run it on the test stand first and see how it runs. I may sell it to help fund a Saito Fa 62 for the plane. You may just have a defective unit. Send it in and see what they say. Horizon's tech support and service are first rate.