Dave,
I have a YS-140 sport that I have been very happy with so far. Yesterday it just stopped running mid-flight. I was at half throttle and done one snap roll at the top of a loop, completed the large loop and flew 50+ feet level when the engine just quit. It was high enough to land easily but I don't want a repeat. The engine had three gallons of fuel run last year (20/20) when it was new and was stored for the winter. When I did get it out it was a little difficult to start but ran fine after a tank. I flew with no problem. The second time out for the year was when it stopped. I ran a tank on the ground with no problem. The tank and lines appear clear and the clunk seems OK. It is a central hobbies tank with their NMG muffler in a QQ 72" Yak. Is there something else I should check? I hate to be stupid and just fly it and have the engine cut out at the wrong time. Incidently, when the engine was new, it had a problem with the throttle barrel rotating and you advised me to send it in for service. It has worked great ever since. I thank you for your advice last time and for this time. Thanks