KY-Ralph

I have the following problems with a built 1983 SE SR 250 to 13kW: The bike was standing 4 years and was moved only sporadically. It does, unfortunately, only after an oil change, new spark plug and cables, and cleaning the carburetor only a top speed of 80-85 KM / H (with one person). In 4th gear you can turn minutes to almost 8,000 rpm (longer trust I am not), but when fifth in the Gang turns it rotates only to max 5300 rpm and has no power to say of slight slope they will be slower. Any help obout this problem ?? excuse my bad english.