Actually my bike engine noise is heavy. left side of my engine sound hears like . if you are changing the gear at that did you hear one sound like(dak,,,dak...dak...) at that sound. when iam starting and running the bike the sound is hearing very high one day i give it to the mechanic to clear the problem. he opened the engine and he says the bell sound is that sound and he tight the bell and he clear some dust metal pieces also and again the sound is coming very high the mechanic said they don't know about that so i check with another mechanic he said time machine problem and another mechanic is saying carburetor is problem and now two more day engine oil is also leaking. please suggest me what should i do. now my bike condition is poor.