Right rear is easier to install. Any one will work tho.
da prez
Agreed, 5 is easier than 6 to instal. 5 being on the right-side of the bike nearer the backside of the petcock.
The reason why 5 is used is that some people disconnect the vacuum hose at its lower end (5 or 6) instead of disconnecting the vacuum hose from the petcock at the upper end, per manual. But, without desmogging there's a lot of clutter to snake the vacuum hose down on install. If you haven't desmogged it's probably better to disconnect the vacuum hose at the petcock at the upper end. Plus the length of the vacuum hose was designed for 6.