Manual
Hey Tiger, You could probably use almost any 66/80cc chinese engine manual. Any major difference would be internally and the manual wouldn't cover that anyway. Also, ( I'm looking at one now,) They don't give the bolt, stud and nut sizes in the manual, Just a general installation guide. A lot of times their written in pretty bad "chinese" english and low quality pictures. you could also write or e-mail whoever you got your engine from and see if they'll send you one.
All this being said, If you already have your engine installed a manual wont be of much use except for a small maintenance section. You can get that, and better information, right here on this site. RIGHT NOW, for now, take off the clutch side (right side) cover and lightly grease the gears where they mesh. Not too much or it may wind up on the clutch, (and thats a bad thing). Then take off the clutch lever (left side) cover, pull out the clutch rod, ( be carefull, theres a bearing inside,) and apply a little grease to each end, and the flat part of the clutch lever where it pushes on the rod. Other than that, just make sure all moving parts are lubed properly. If it moves it probably needs grease or oil. Good Luck.
Shiney Side Up,
Big Red.