Not to worry much..that rattling sound may be from the tappets, which is pretty common for most of the ZMA's..!! Regarding the engine's harshness..which can only be resolved by resolved by an oil change.. since your bike is pretty new, hence its bound to happen and it will decrease as time passes by..!! Once you cross the 1000-1500 mark then you can shift to a fully synthetic oil which lasts long as compared to the HH oil. But till 1000-1500 mark stick to the HH oil only...its best for the new engine..
Hope it clarifies your doubt..do lemme know if you need anything else too ..
