Hi Peter – Welcome onboard! Prepare to give your credit card a good kicking! In terms of tweaking a GS, I’ve had a go at the following (in this order):
1st: Y-piece – made the biggest single difference, more mid-range, easy to do but be careful to seal it properly to the standard end can. Considerably lighter than the cat and makes the bike sound nicer without being anti-social.
2nd: Remus Revolution end can: makes no perceptible performance difference by itself so just about whether you like the noise, many (me included) prefer the baffle out as it makes a deeper, less annoying noise at motorway speeds. Some try it, don’t like it and re-fit the standard can so if you’re interested but not sure keep an eye out for 2nd hand ones on here. If you use panniers you may also need to stick on some heat shielding to prevent unwanted melting!
3 rd: K&N filter: does make a very small difference at the top end (I have the dyno graphs to prove it).
4 th: some form of chip/electronic tweak: mods 1 –3 make the bike breath easier and consequently run a bit lean. I’ve added a Techclusion R259 black box which richens the mixture and makes it run a lot smoother and pick up easier through the gears. Makes little performance difference but still well worth it for me.
There’s loads of discussion on here on the pros and cons of all of the above – find a comfortable chair, do some searching and settle in for a weekend’s reading!
Andy
