All those who are speaking of noise in idle then i think they have not heard engines of modded cars and bikes. That is not noise but valve clatter. It happens because the valves lift a lot and then bang back when the cam leaves the rocker lift. Since the high lift camshaft has stiffer springs for valves to return quicker at high speed so at idle the sound is heard as valve clatter. It is no way harmful or un pleasant.
In fact the sports model has little un even idle. But as revs climb the clatter reduces.
Its not a defect but effect of tuned engine. Only way that sound can be suppressed is by water cooling which the water jacket will absorb the clatter.





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