squeak
First, Kill the mouse. (just kidding)
It probably is just a new clutch. Does it do it when the clutch is in? Be very carefull with grease around the clutch. You only want to put a dab or two on the drive gears only. Too much and it will sling onto the clutch pads and thats not a good thing. Also, There's a press ring that holds the clutch together with tiny bearings under it. You'll have to take off the clutch plate to see it. VERY CAREFULLY put one or two drops of oil on the bearings. Again, too much and you will sling oil on the pads, a bad thing. You'll have to adjust your clutch after you get it together again. You do that with the flower nut that holds on the clutch plate. I don't know why those silly chinese people would put together an engine without lubing it, But they do. The new pads sometimes do squeak some. It should stop with a little break in. But do the lube stuff anyway.
Big Red.
P.S. As you're sitting on bike, Clutch cover is on the right.