My bike revs high when i give it gas and picks up speed slow?

Its a 1989 kx250 it sat for awhile with a hole in the gas tank so i put one on it and got it runing but it wont kick start unless you have just cut it off.But if you push it it will crank and idle but has a funny smell.i just put amzoil oil in it and i looked in the bubble and its already gray.The bike seems like if it would just go it would be fast like the motor is reving up high enough.Seems to me like the clutch isnt letting it go kinda like its in between gears.Please Help.it seems like the clutch is there and then you can have the clutch in and it in gear and it will pull.like its not engaging