I'm just curious, I have a 66cc slant head grubee skyhawk on my bike that has a standard finish (and is covered in oil) and I also have an extra engine (66cc, I think it's a PK80 but not sure) that is not a slant head but has the nice black finish to it. I'm considering on swapping the current motor out with the black one but I'm worried about power loss. How noticeable is the difference between slant and non-slant?