Hello, I just got into mopeds and ppurchased a 1978 Newport "L". It runs pretty good. I started to check it out when I got home. I noticed that the rear tire was spinning at idle so I adjusted the carb speed and slowed it down. I then noticed a clunking in the tranny which goes away when you give it power. It is not heard when the wheel does not spin and only when the clutch is just starting to grab. Checked the fluid and there was none. Filled it with ATF type "F" ran it and drained it. Filled it again and seems better except now it is slower coming ff the line. Question, what inside the tranny would causes the clunking?