How can I tell if my 50cc 4 stroke scooter throttle is wide open?

[willmon22]

My throttle was very loose so I tightened it at the carburetor and at the throttle. Before I did this it was going only 35Mph and it usually went up to 45Mph. Well after I had adjusted the throttle and the idle screw to where the back tire spins just enough to where I set it down it will almost move without brakes it goes nearly 40 on a flat surface but not all the time. Sometimes it goes down to about 35 and won't go any faster. Also at first it sounds like the throttle is all the way up when I am holding the throttle about half way but once I go all the way up or get up to speed it sounds like it throttles down. So I am thinking that I am not getting the throttle all the way open or my carb is dirty. The scooter has a little over 3.7K miles on it and I haven't had it cleaned since I got it and it had about 500 miles on it when I got it but the odometer cable was unplugged so it may have had a little more on it or it just came undone in the wreck that it was in. Anyways I am just wanting it to go up to 45 again as it is just not going fast enough especially up hills. It use to zip right up a hill at 30-35 and now I would be lucky if it even gets up to 25.