HI! When i accelerate in 5th gear with moderate throttle a rattle developes...much like the sound of a chain rubbing on something. But, if i hit the throttle aggresively no rattle sound?? So what could it be?? I've check the valve shims, that didn't make any difference. The timming chain is "snug" and the tensioner seems to be doing its job. Although the "pin" marks on the cams realitive to the cylinder head is not perfectly horizontal (WR Timming) ...possible stretched timming chain?? - maybe its time for a new timing chain?? Also, when lining up TDC, the motor has a tendency to "fall" out of TDC, in other words it rotates clockwise about 1 or 2 degrees off of the "I" mark. Is this normal?? I currently have the top end ripped apart and took the the cylinder head in for inspection at a local yamaha dealer- they checked all valve seats, springs...etc. So thats all right. The piston looks good too, but i have to double check my specs more throughly later tomorrow. So, since i have the engine opened up...does anyone have some suggustions on what it could be or experienced the same problem?? Thx!! Aside.... The service department at the shop said it could be a multitude of things....piston collor/pin slack....exhaust....air leaking in somewhere(??) But at $80/hr cdn (robbery!!!!!) +tax...i'd like to avoid them as much as possible---they already doubled the cost estimate to look over the valves---piss me off. The parts department at the shop says that it's the chain rattling on the suspension...but i've looked into that and from what i can tell.... no issue there.