ring is not turning on piston as ring is held in place by the pin in the piston, checked that. i think it's possible that timing senor may have moved abit as screws could be tightened about half a turn each, i dont know how much movement matters though. if it moved 1mm would it make a big difference? i think this is the key to my problem here! engine runs like a clock, very smooth and consitant at any rpm, even full throttle. just not pulling hard. feels low in power at all throttle positions. it used to feel like it would rip my arm off at full throttle when i used to rev it on the ground, now it's more like a firm pull.