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

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.

if you pull the air cleaner off you can see the throttle plate inside the carb

Ok so I pull it off then and after that I just pull the throttle all the way open and should I push it further to see if it will move? And if it does move should I adjust the throttle and then adjust the idle screw if it goes too fast when it is idling? I am fairly new to trying to tune up a scooter and make adjustments and stuff. So I will need specifics.

how does your throttle cable look on the side of the carb?

if your throttle cable isn't stuck or sticking, you can try the idle screw. I heard that sometimes the throttle cable sticks.

I don't believe it sticks. As at the carburetor when I pull the throttle all the way and let go it goes back to its normal position.

i'm not sure whats going on with that but it wouldn't hurt to clean the carb. It's pretty easy. I just did mine.. I'm just trying to figure out how to adjust the air fuel ratio to a good setting

There is youtube videos for that. I guess i will take my filter off and see if anything is dirty and see if the throttle opens all the way. Later i am just going to put some startron in it.

Well I had just took my air filter off and it seemed like there was a little bit of black stuff in the air filter and in the carb. So I had cleaned that out with a shop towel and took it out for a ride. It seems to be performing really well now. Even with all this wind it is working good. Sometimes I can get it to just 35 but of course there is some strong winds out. And when I am going on a flat surface I can get it up to 50 and it is wanting to go a little over that. Crazy thing is people were still passing me up for no reason. Some people are just impatient and just want to go over the speed limit to pass me up. My only question is what is this black plastic piece that is in front of the throttle slide that seems to be spring loaded. I had to push it up a little to actually be able to see if my throttle was getting wide open and it appeared that it was. As I pulled the throttle and I heard a click when it got all the way to the top. I even tried to push it up and it wouldn't go any further so it has to be getting fully open. I also added about 10-15 ccs of startron in it so maybe it will clean the carb up the rest of the way.

Are you sure the black plastic thing isn't the throttle slide? You would have to lift it up to see the butterfly in front of it. The slide is lifted by vacuum from the engine.

inside the venturi of the carb there is a round plastic thing. That is part of your diaphram in your carb. you should be able to push it up easily into the roof of the carb. If you take the top of your carb off you should be able to pull it out. Just remember to relalign the tab if you do that. It should not be stuck.. if that's the thing you're talking about.

Yeah, I think it is part of my diaphragm. As it doesn't move unless I push it up. But I could see the metal throttle slide go up as I pulled the throttle.

http://www.bing.com/images/search?q=...electedIndex=0

Cutaway view of a carburetor. I see the butterfly valve and slide that's lifted by the diaphragm. Is there something else in yours?

http://www.bing.com/images/search?q=...lectedIndex=17

I guess it is a butterfly valve. As it is in front of the slide and it goes up if I push it and feels like it is spring loaded. But I really don't know. If I get the chance I will take a picture of it at some point.