Parts are painted before being machined, the 'bare' metal you are seing is normal where there is a casting miss match between components & the parts have been faced off during machining (also normal) Shows up far more obviously on black engines. just ACF 50 & enjoy the bike
Mac
If you look at the front of the engine where the engine bar mounting will fit , it is bare metal. I used high temp grease on that, probably I will cover the bike in the stuff AF50 is for girls