Bike is loosing all power when you give it more than half throttle

[Johnstons10]

I just got given a secondhand bike that starts fine and runs fine in the lower rev range but when you go to give it more than half throttle the bike starts to splutter and loose almost all power is it a carby thing or is it sum thing more serious it is a 150 cc orion with an upright motor but I don’t now hat model it is

 

[sean01]

check the valve clearances (search the forum here for tutorial)
clean the carby and air filter out and replace the fuel filter

 

[motovert24]

mabye crap or water in carby