Hi Horrido,
Here's my pick in order of personal preference:
Taurus 2.6 or 3.2
BME 50
ZDZ40
Brison 3.2
First, they are all excellent motors. IMHO, although the Taurus is the least known, it is of the highest quality. As a part of Southgate Aero, they have a long history of producing quality engines for many applications. I've personally owned many gas engines, and seen most of the rest run, although the a BME 44 is the only one out of this list that I have owned. The Taurus has a superior designed bottom end and uses only the highest quality parts throughout. Again, from my experience, they start easily, are the smoothest, most powerful per cc, and have a great 3 year warranty...and no, I don't work for them. I was dragged kicking an screaming into getting my first Taurus a few months ago and I was so impressed I've had to spread the good word.
Their Web site is
www.taurus-engines.net. It is not very up to date, as is the case with most R/C(and other) Web sites, but it will give you some more info.
BTW, all of them weigh within a couple of ounces of 4lbs with pitts-style muffler, ignition and mount. The ZDZ is about 5-7 oz lighter than the others.
As I said, the other motors are all excellent and you'd be happy with any of them....you'd just be the happiest with the Taurus.
Bill