Hi,i have bajaj discover 125cc,2007 model,the problem is the performance is decreasing day by day,i hav been serving it correctly time by time,,but still it make noise,i changed chain sprocket,oil,the thing is when i change from neutral to 1st gear,it makes irritating sound,engine maked sound,but service man says trs no problem by engine,but still its not running smooth..wat should i do nw,plz help how to solve it.. thanks -sri moons-