Suspension setup for a FS650 SM

Hey everyone I just recently purchased a 2006 FS650 with a supermoto conversion and I was thinking of tweaking the suspension a little. I am around 80 kgs and would be doing the majority of my riding on the street with an occasional swap to knobbies for some trail riding. I have not done any suspension work before so I figured the 'Berg would be a good bike to practice on. I haven't had a chance to ride the bike a whole lot yet but in the few rides that I have taken it has absolutely won me over, fantastic power delivery and way lighter than my old Suzuki SV 650!

I prefer an FE with street wheels rather than the other way around. gearing is murder because if you short shift on tall gearing you end up doing 110mph in first at idle and the scenery is going past very fast indeed.

I'd say to enjoy both shen starting with an FS is damn near impossible!

regards

Taffy

Shim Restackor is a suspension simulator: Shim ReStackor, Finally software to tune a shim stack

It's great! I came in knowing very little and ended up building custom valving for my DRZ forks with it. Really brought the bike under control. Very satisfying work. I learned a bunch from this thread: https://www.thumpertalk.com/forums/...evalve-shim-stack-discussion-recommendations/

(It's certainly possible to bring an FS closer to enduro behavior.)

I 2nd Taffy. The stock FS 8.8 shock and 48kg forks with street valving is not what you want to deal with offroad. My 06 FS650 conversion.
I set up my 07 550 to do both with shortened. 06 enduro shock and raised forks for supermoto. It works surprisingly well with just the clickers stiffenned up for that purpose and can still be used offroad clicked the other way. But I do have the complete 07 enduro suspension, wheels and triples on the shelf when needed.

pollo

Since I am starting with an FS anyway, would changing out to a larger rear sprocket in addition to some suspension tuning help bring it more under control off road? I did notice when I was riding it home that it certainly likes to be in the higher revs. I won't be racing or anything like that but the main reason I would want to be able to do offroad is just to be able to go out for a weekend now and again with some friends.

If you can bare it huss try. But at 175lbs I would imagine you could go all the way soft with FS suspension and still get beat up on the trails.
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This is entirely doable. Best now to gather some information and get a feel for what you want. Have you had the bike out on a trail? How did it feel? Have you had the opportunity to compare to other bikes? Let's figure out what's good for you. It would be great information for this project if you could take your FS out with some friends' bikes to swap and compare.

Personally, I'd rather have a bike too stiff on the trails than too soft.

There are lots of things you can do. Let's set gearing aside for now; It's easy to solve IMO (just a question of sprockets). Especially because the 650 has such a broad power band AND a six-speed wide-ratio gearbox. We'll easily find a solution for gearing, whether it's a fixed set of sprockets or different sprockets for trails vs. street. Gearing Commander should help: Gearing Commander âš™

There are a few different approaches you could take.
- Just ride it as-is.
- Adjust the clickers, see if you can find some good settings for trails vs. street.
- Revalve the suspension. This is wayyyyy easier than people think. At least now that we have good damping simulators. The mechanical job itself is easy.
- Get a set of FE front forks, front brake, brake lever, and wheel and swap that in/out of the clamps. This is a quick swap. You'd be surprised. Easier than changing the front wheel. (I don't know if it's realistic to swap the rear damper back and forth like this. Maybe? I don’t know how quickly that can be done, but I believe it’s more involved so we’d probably leave that off the table.)

The biggest differentiator is the damping curve. This is mandated by the valve stack inside the front and rear dampers. Mostly you change the compression curve to fit the intended use. I’d hazard a guess that the FS’ compression damping is quite high, and probably rather stiff in the low-speed region. Probably stiff in the high-speed too. For trails, I find plenty of high-speed damping is fine, but I could imagine that you’d at least sometimes want a little less compression damping in the low-speed to get the suspension to float over trail trash. By nature the compression dampers mostly affect the low-speed damping, so you can probably get a ways there by just loosening up the compression clickers. If it still feels hard, then I’m 100% confident that you can pull your front forks apart, measure the shim stack on the compression valve, and simulate a new stack that works mostly the same on the street and can be turned to softer on the clickers.

Other aspects are the fork offset which affects front wheel trail which is different between the 17”/17” and 21”/18” wheelsets, and the front brake size. It’s entirely reasonable to find a balanced compromise. Spring stiffness doesn’t really matter that much. This tells you why: Spring Rate Selection … basically with a stiffer spring the suspension can act faster and will actually feel PLUSHER if valving is right. At the crazy stiff end you start running into issues with rebound damping if you take compression damping way out, but it’s solvable.

But start by get that bike on the trails and see how you like it

Note also that the tires are part of the suspension. If you can run at lower pressures then that can take the sting out of harder hits. I mean you can always just deflate but that creates the risk of flats, but there are ways to go tubeless. I believe a TUBliss tubeless setup in the knobby wheelset could be useful in your case. These help by allowing you to run way lower pressures than with a tube.

Careful selection of tires can also help, something with a strong carcass.

Most guys I have seen wanting to go from FS to dirt end up swapping suspension. Just what I have seen.
The thing is, you can go into valving and all, but you will also take away from how good the bike is as a supermoto if you ever want to get serious about it. But more than that is that if it is a true FS it has the shortened suspension along with the Radial brakes and 310/320 rotor. Not something I would think you would like offroad even if you got it to fit. The supermoto wheel needs offset to go on the enduro suspension and I imagine there are fitting issues trying to get the enduro wheel to fit the FS forks and caliper. Im not even sure I have seen that. And the brakes are very powerful. And watch out for the 320 rotor in the rocks. The FS fork leg will not take the enduro floating brakes with smaller rotor either.
You can pick up a set of Ktm enduro forks for about $250 on ebay if you cant find Husaberg. The shock for about $100. And the thing is, your FS forks and shock are a wanted item. They would probably be snatched up quick if you sold them. And would probably get more for them than enduro.