I have some experience with the XYZ 26cc A-spec.
at first look, it seems like a good engine, the crank is CNC machiend, walbro carb... nice engine.
ran it for the first time with a 17X6 APC prop.
after initial break-in, the engine starts easily, turns the prop at 7500rpm (thats for a new engine).
ran it rich for a galon of fuel (while flying) and started leaning the top-end.
i had two galons of fuel throgh it (95 octane, fully synthetic motul oil 1:33) and now it spins a 17X6 prop at 8000rpm - thats rather nice for a 180$ engine.
for high (relative) static thrust, i used a 18X6W APC prop, the engine turns it at 7100rpm and the plane (11lbs) has unlimited verticals.

the engine was mounted on a funtana90, had a lot of fun with her till i crashed her - it seems that this engine cant work without fuel
mounted the engine on a extra330, once tuned - the engine perfomed fantastic.

problems:
Had some problems with the connector of the hall sensor, replaced it with a standard servo connector and the problem was solved.

pros:
Its a nice engine, great value for money, easy to tune, lightweight, friendly.
will replace any 1.20 glow engine.
very low fuel consumption.

cons:
the muffler is rather large, could be replaced with a wraparound type.
problem with the hall sensor connector, easily fixed.
not as powerfull as the zenoah or MVVS (but for this price, i was very satisfied).