It was running fine last year when it was put away. It has new fuel and i sealed the two gaskets at the carb and the intake to motor. It starts up and idles fine but i just cant get it to rev past half. I have sprayed carb cleaner to clean it. I have tried with the fuel screw all the way in and out to 2 turns, it seems to get worse the more i turn it out. Its no different with the choke on but choke makes it worse when its warm.

 

Try a new plug, and check the battery voltage isn't going over 15v as you rev it up. Probably is a carb problem though, so clean the jets out with compressed air, if the electrics are OK.

 

Any chance a mouse built a nest in the air filter box and restricted the air flow?