I have a bad rattling noise coming from the left hand side crank case any idea ? yamaha 350 banshee year 2005' i have chosen an rd 350 because it doesnt let me choose a banshee

Could also be piston slap, how many hours are on bike since last top end rebuild? Alot of times worn pistons, and or piston pin will cause a rattle. Its just easier to hear on the left side.. Check out ASAP because either one will be expensive if let go to long. I cant imagine a flywheel or stator problem if it has rattled for a while because these are pretty delicate parts that when they do begin to rattle it throws off timing and the motor will not run. But if it has just started to rattle it is possible.... Will bet its piston slap, if not the Crank Shaft and or bearings..... Could also be piston slap, how many hours are on bike since last top end rebuild? Alot of times worn pistons, and or piston pin will cause a rattle. Its just easier to hear on the left side.. Check out ASAP because either one will be expensive if let go to long. I cant imagine a flywheel or stator problem if it has rattled for a while because these are pretty delicate parts that when they do begin to rattle it throws off timing and the motor will not run. But if it has just started to rattle it is possible.... Will bet its piston slap, if not the Crank Shaft and or bearings.....