I liked the 3MM - TOC 53cc that I bought from Tom at Wildhare, also. He, too, provides very good service, and is quick to address questions, shipped almost before payment got there!

I think the 53 may be heavier than some others, because of the front crankcase design, and I know that helps make it an amazingly-smooth 50-cc-class engine. Mine was smooth as anything I've ever run, including the Taurus T-52 (which is also a 50cc class engine).