Popping out exhaust, loss of power, wont run at full throttle.

You might try changing the fuel line itself. Do this especially if anyone has recently changed them. Though heard of less these days than in the past, some fuel lines will separate and actually close up somewhat once it gets warm. This is usually accompanied with a significant bit of backfiring and popping.

it sounds like your carb is gummed up. You can TRY something called SEA FOAM (you can get it from Napa), you put it in your gas tank. It's the poor man's tune-up. Otherwise, you can get some spray carb cleaner and pull off your air cleaner and spray it in there. Hope that helps.

Sounds like a fuel system delivery issue! Have a professional clean the fuel system and clean and set the carb. A new or CLEAN AIR FILTER is required.

fuel filter clogged or fuel pump problem

Pumping the primer bubble while the engine is running should cause the engine to over fuel and stall (if the tuning is correct). Sounds like its not fueling enough, pumping the primer is forcing fuel through the carb causing the engine to pick up rev's, but this is soon exhausted which is why it wont rev on the throttle.
* Check that the fuel line is not damaged and drawing in air. (if this is intact try the next step)
* Strip and clean the carb. Replace any diaphrams if needed.
* Check gaskets seal between carb, air filter and cylinder.

Just out of curiosity what standard carb settings did you use.?

take the carby in to have it assembled correctly
the positioning of the gasket on the right side of the diaphragm is critical

You can find out how to adjust governor on you -tube. give it a try.

Take off Air filter, look inside the carb and pull throttle all the way, the circle should be fully open, if not it may not be getting the full amount of gas it could be, Clean the carb as well, take it apart and clean the mesh filter, To check your plug, just unscrew it from engine, put the cap on the plug, place the tip of the plug on something metal and pull start the engine to see if its sparking. I think you have a carb problem though, clean it and clean your filter and you should be good. If its a stock engine on a goped sport than you should mix 3.2 ounces of oil per gallon. Hope this helps

Since you don't indicate the make and model, I can't give you specifics, but when I had this problem it turned out to be a dirty carb. This can cause uneven fuel flow and loss of power. At full throttle, you may not be getting sufficient fuel to work properly. Try cleaning the carb a nd update this with the results.

Dan

Sounds like the carb has not been cleaned properly, gas overflow like that could be caused from a worn seat/needle. Did you put after market exhaust on it?