What oil is moat recommended for Gen2? I've noticed only part synthetic is used? Also, there is a longer oil filter...do any mods need doing for this?

Many thanks in advance 

That old chestnut

There will be many opinions. I use Motul 5100 15W/50 Semi and have done since the bike was new.

These engines were designed before the widespread use of fully synthetic oils and the component clearances make a semi synthetic more appropriate.

I have always used a 50 weight oil although some say a 40 is fine. Given the huge power pulses that come from the V twin I prefer to keep with the slightly heavier weight oil to help maintain the oil barrier layer intact.

There is a theory that you need to stick with whatever has been used before as mixing the use of semi and fully synthetic can cause problems with clutch plates. I cannot confirm or deny as I've always used the same oil but I've heard it from a number of sources so I would just keep using what you have been.

10/40 or 15/50 whichever you fancy is perfectly acceptable. 

I ran 10/40 on my big bore and race bike as recommended by the man himself.

As for filter look at the oil filter cover. If it’s practically flush it’s the short but if it’s like a top hat and is proud of the engine case it’s the long one. 

Short tended to be about up till around 2005/6 and the top hat style after. But check the cover to be sure.