Hi -
Well....it's like this, J330, most of the guys in ALL the clubs I have been with have owned and flown dozens of planes over the span of their hobby-life. Most of these planes have been ARFs. As such these guys know how to open a box, use a few basic hand tools, and assemble what comes out to be a dang nice looking airplane with all the spiffy finishing touches. They throw in an engine and they go fly their shiny new plane. They may have 100s of hours of flying time and may have been in the hobby 40, 50, 60 years. If you ask them, though, what do they really know about an airplane the answers I have received are, "truthfully, not much."
It is a far cry different to build a model from a kit or even from scratch like I do, have thoroughly studied flight principles and aerodynamics like I have, are able to differentiate high quality building materials from poor like I am, and truthfully call oneself and "expert" modeler than it is lie about it and say the same thing when all a person has done is assemble parts together from a box.

That's what I am saying about my knowledge and expertise with engines. Yes, I have owned and operated many different types of engines in my life. Have I tore them apart, inspected how they've been manufactured, assessed their performance...etc. like many of you have? No. We all have our strengths; we all have our weaknesses. I am a mechanical engineer by education and training. I've designed dozens of electro-mechanical tools and pieces of machinery in my life. I know the mechanics of engines pretty well, but I am not an engine designer. I know when my car engine is running correctly and how to maintain it properly, but I am not a certified engine mechanic.
So maybe it seems odd to you that I am seeking input from fellow modelers, but the wisdom and knowledge that all of you guys (and gals) bring to the table far surpasses my own. Hence, it's wise of me to not rely on my own judgement, but to also seek that of others. My dad - God rest his soul - could run circles around the very best electricians, plumbers, and HVAC people out there, but all he had was a high school education. Do you get my point?

The voting tool only allows for 4 selections otherwise, yes, I would have included Saito, Thunder Tiger, Super Tigre, NovaRossi, MVVS, and many others. As it is, I included only those engines that I have some practical knowledge of. And in truth, I am not bashing OS. If you read my posts all I said was that the OS 61 FX I have has never run right and that other people whom - right, wrong, or indifferent - I have considered "experts" couldn't get it to run right either. Does that mean I don't like OS engines? No. It just means I have few data points of comparison with them, which is again why I am seeking advice from folks such as yourself.

I guess I should have qualified my request better. From my limited knowledge from only sources of reading, JETT, Rossi, and NovaRossi engines are very high performance marvels intended for racing or competitive applications. Truthfully, though, I didn't know NovaRossi made anything other than buggy/car engines. True or untrue I don't know. The Moki's I have had all were excellent engines, too. I like my Saito 125 GK. What I am trying to get a better picture of, though, is why some engine brands are vastly more sought after than others?
Over the years I have heard and read dozens of views and opinions about Super Tigre (for example). If you go onto EBay or RCU, folks are unloading their Super Tigre engines for incredibly low prices, why? I see the same thing occurring w/ OS engines to some degree. And when you watch these auctions and see that there are few takers logic dictates that you have to question when so many fellow modelers see these ads but are passing them up, does this mean people are questioning the quality and reliability of them from their own experience or does it mean more so that more and more modelers are choosing to go electric and gas due to the cost and messiness of glo-fuel? My guess is that it's probably the latter; I don't know that for sure, but when I read articles online I am gradually learning that the quality of Super Tigre may have declined dramatically when the manufacturing moved to China. OS on the other hand seems to be making steady strides to ever improve their engine quality and performance. Despite my limited experience I would have to argue that going w/ an OS engine is a very safe bet.

I tend to agree about going 4-stroke, which is why I have been seriously looking at the OS Alpha series four strokes like the 52 and 56. The reviews are really great for these.
With all of that being said, I am just trying to make a wise decision on my next engine purchase and I cannot emphasize enough how much I value yours and everybody else's view and opinions above my own.

Tom