Ive never seen a 10" wheeled agility but they must exist
Yep, they do... I own one, but compared to my 12" it feels a bit smallish and unstable.
It also looks funny when parked next to a 12" version, the top half is exactly the same as the 12", the bottom half is different, with small wheels, shorter engine case, shorter wheelbase, the front fork is thinner and less wide, and overall height is 5cm less...
Anyway, on topic : I wouldn't buy a 139QMB engine for a Kymco..
With those generic Chinese engines you never know whether it's just as good as a Kymco one, or whether it's made on a Monday morning by the cheapest manufacturer of the planet....
I hear a lot of disturbing things about this generic Chinese stuff... I would rather fix whatever is wrong with my machine, even if it means a complete rebuild - heck, It's probably even safer to buy a second hand Kymco engine instead of a shiny new 139QMB...