Thanks, look for wear grooves in both. Also for wobble in the shift shaft claw pivot. The shaft shouldn't move when you put pressure on it. If it does the shaft could be worn and the white bushing that holds it from sliding to the left, the cover has a bung on it that holds it from sliding to the right. All things to look at.
It's probably one of those things listed above inside the clutch cover, but first check that the shift lever is tight to the shaft and has good splines.
My specs are below, I rode at 1500ft all summer, and never ran out of fuel at WOT (for as long as I cared to hold it there in the dunes) with a stock petcock and tee.
It easy to get the cables twisted up when you pull a topend. make sure the slides drop completely at the same time or straighten out the cables. gas overflow is a sign of float adjustment or needle valves not sealing. black on slides is normal.
You should see if the guy you bought it from might still have a copy of the invoice from F.A.S.T. for the motor work, it will come in handy. Or at least give you a list from memory to give you a better idea of what you bought. You eventually will need to know.
I'd say you're due for a top end. The next time it doesn't want to kick start hot, try pouring a little premix oil in the spark plug holes. If it fires right up, its your rings. Or worse.