1981 honda 125xl s help!!

Ok i will be the first to admit im a car mechanic not a motor cycle mechanic lol i know nothing about bikes but how to keep them runing (somtimes) Anyway i got a honda 125 xl s at a good deal from a cousin who gave it hell. It runs pretty decent smokes a little, but now its starting to where if you get down on it like while your doing 20 mph or more, the engine will raise up like it should sounding like its about to haul butt, but the bike itself isnt picking spead up that fast sounds like the motor is runing way faster than the bike itself. Any idea's?? does these bikes carry gear lube? or does it all run off of the oil?? i have no idea so any light into this subject would help thanks! :whoa:

ok the clutch at where u pull your side cover off where the kick crank is? and it looks almost like it has brake pads on it? has like 4 springs with bolts ran threw it? becuase that is what i was thinking becuase i have a friend with a 4wheeler with kind of the same problem. But is that the piece i need? or is the clutch somewhere else? Also i was thinking of putting new rings in this bike becuase it smokes a little would or is it possible to port out the carb/ intake/ exhaust and block to give it more power?