i recently got mine!!!i broke in the engine on saturday...the engine looks to have better rpm all arround , from bottom to high end.I didn't push its limits as it was just broken in and worked fine and stable at 82c temperature.The engine should screram like hell if worked arround 100-110c temperature.Moreover after the brake in i should take off one 0.10 head shim to increase compression as i run 16%fuel and it comes factory set for 30%!!!!

During the brake in it never flame out , not even the slightest problem and trouble.I suppose the Japanese people have made one of the best engines arround and value for money.I'll have more specs on next saturday!!!

fuel consumption seems to have been improved as well , as i had more than 7 min run with one tank.that will sure be dicreased when the engine would be 100% ready for racing after about half to one litre of fuel run!!!!

Just one word discribing the engine : AMAZING!!!!

THE XZ VERSUS THE SPEC 2 seems to win at all categories:

fuel consumption
all arround rpm
stabiliness

although the specs are published as same as the spec 2 , the xz has absolutely more bottom and top end..especially the top!!!!!!!!