Guys....I have flown nothing but BME for the last 5 years and never have ducted my cowl for cooling my engines......and have never had an over heating problem.....lived in Georgia the last 3 years and just moved to Florida so its hot. I truley believe that if people would stop tweaking the heck out of them to to get every last RPM they wouldn't need to be concerned about cooling. At the same time I do believe certain installations and cowl design obviously can affect cooling so I can see it as an issue in some cases.
Also during this time I have run nothing but Amsoil.....100:1 1st then the 50:1 the last 2 years and prefer the 50:1. I will never ever use lawnboy again for break-in either....I did that a few years ago on a BME100 and it carboned up stuck rings and I had to send it back....whcih led me to think about the problems I used to have with my Quadra and Brisons. I run Amsoil right from the get go set rich and my last 2 engines have come on beautifully for power.
As to a motor running a certain amount of time and then quitting.....well that has nothing to do with the motor itself....it wouldn't take any more than a minute for a problem to show up, if that. As someone said in an earlier post you can usually side with user error....and if a user is too hard headed and usually not as smart as they think they end up with problems. My guess is that its an ignition issue....I have had cases on some singles in the past where after a while it would start missing in the air badly and come down hot. After cooling it would run fine on the ground...then I'd take off and in a few minutes the same problem. Each time I would send in an ignition CH would replace the leads and my problems were solved. Seems the materials in the leads can and do break down over time and when they get hot the insulating characteristics worsen and the problem shows up. It doesn't take much to picture that exact scenario showing up after a certain amount of minutes each time.
Perry