I am trying to help my grandson with a Buyang 70cc 4 wheeler. This was an almost new bike that set until the gas in carb turned to varnish. My son took off the carb and cleaned it. Now the unit will only start with choke on almost full and when it does it runs at a very high rpm. I have set the fuel mixture screw at about 2 turns out. The throttle body is inserted with the grove in a position that allows it to close completely. Because I am not the one who originally dissembled the carb I am at a loss on how to proceed.

Do I need a new carb? If so where can I purchase one?

 

Welcome to the forum rlewis!

More than likely the carb didnt get clean enough... You need to be able to see light thru the jets and thru the holes in the side of the main jet holder..

 

Thanks, I will give it another cleaning tomorrow.

 

Remove all the screws and jets... use spray carb cleaner and compressed air if you have it to blow thru all the passages....especially the small ones..When you put it back together turn it upside down with the float installed...The float should appear level if its set correctly...Id guess its ok but since youve got it apart Id check..

 

I have the same quad (Buyang 72cc) and I seem to have the exact same issue. The bike will start after some tlc and only idles full choke, or wide open. My quad was abused by the previous owner, and amung issues, all of the vaccuum lines were disconnected. There seems to be two bungs on the air filter for vaccuum fittings, and I believe one is for the crankcase. The two vac lines off the carb (1 from the float, another off the main port) I am not sure about. If anyone knows where these lines go it would greatly help.
As well the carb has been improperly tuned and I am not sure where to start on adjustments (float, idle, ect). If anyone has a good starting point I would appreciate some advice.