Howdy-
Suspension settings are a grey science. And even at the pointy end of talent, two riders with the same bike can end up with rather different settings and go equally fast. Some like the steering fast and twitchy, some like it neutral or other set ups.
My preference is for a set up that is a compromise between as firm at the back and as quick as possible steering but softish on the front (for feedback) that is still ok for the road. I also often ride two up and that is a total of about 165kgs. But then I also like to be able to do a track day without fiddling.
A few "rules" as per Ohlins and Racetech advice and what I have learned from those in the know and put into practice are:
1-Always have at least 5mm more static sag in the front than the rear.
2-About 1/3 of the suspension travel for static sag is usually a guide for a factory type default setting.
3-From 5mm to 35mm at the rear and 10mm to 45mm at the front would be the total range usually considered. For "sporty" handling about 25/30mm rear and 35/40mm front would be most common.
4-The more the rear is raised (sag reduced) compared to the front, the quicker the steering.
5-When a spring is shagged, such as when the static sag at factory default preload is half or more of the suspension travel, get a new spring made for your weight. (Racetech are excellent for this). Jacking up the preload will just make the ride harsher and hardly compensate for bottoming or improve handling. (My rear spring is nearly history-probably because the previous owner pulled a trailer and rode two up.)
I would suspect a new 'Bird would be close to right brand new except for a turn or two down on the preload C ring at the back and a 4mm to 6mm spacer under the rear shock mounting. However, if you usually ride solo and don't weigh more than about 70kg and are not likely to explore serious lean angles, there would probably be no serious need to change anything until the springs start to get tired.
I very much recommend all 'Bird owners establish what state their suspension is in and whatever it is, work in the direction of a good setup, preferably a quicker steering option. It is quite amazing how well an already good handling and nice steering design that it is can be transformed into something quite stunning for such a large and fairly heavy bike.
Make all setting changes conservatively and take the time to ride long enough after each adjustment to think about what has changed.
There are many other aspects that can be discussed (preferably standing next to the bikes in the back yard with a few frosties and a barbeque on the go), so please feel free to question further.
:beer: :beer: