when u tune it ask ur mechanic about it,, srf hath sa chk karna k baad hi banda kch kah saktha hay,,
it could be clutch plates ( pressure plates actually) be worn out,,
plates cost 40-1300 rs depending on quality,,may be u got something ofbad quality last time,,
use original engine oil better havolie from pump itself,,
lube chain, adjust carb, tune tappats,, and check for any leaks on the place where the carburetors pipe meets the cylinder head engine)