I recently Done a Top end Rebuild on my Suzuki lt 80 Because of a engine rattle I put it all together and started it up and it still rattled so i decided to take the bottom end apart to see if it needed a big end bearing or the main bearing but they are fine. Any idea of what the rattle is?

 

Welcome to the forums.
Seeins it's apart, you're going to put new main bearings in anyways. FYI:I use koyo bearings (10 bucks) instead of Suzuki (25 bucks). We'll see if that is it.
Stick a wiseco piston in it? If so what was the clearance set at?
Any problems with the clutch parts?