Fork Suspension Settings
 

Still learning the bike and bringing all the maintenance items current. Searched general tech and found a few somewhat helpful but limited threads.

02 F4i. Forks are bottoming out (very soft) and I want to reset the adjustments back to factory as a starting point. I need to confirm where and how the adjustment points are before I start making changes:

Top center screw
Compression adjustment? Rotate clockwise for full hard and back off 1.25 turns?

Top large nut
Spring pretension. Currently set at 4th ring from top which should be factory setting.

Bottom of fork
Rebound adjustment? Rotate clockwise for full hard and back off 1.75 turns?

Settings are from the service manual. I could not find the "locations" and "how to" info. Probably there but having a "senior moment".
Thanks

If the forks are bottom out, try more pre-load. But really, if you are a big guy,
you may need to go to a heavier spring. There is only so much adjustment
you can do, before you harsh the ride too much trying to compensate.

If you aren't a big guy, check your fluid levels in the tubes. Heck, even if you are
a big guy. That can play difference, too.

Hope this helps, Ern.

Preload will just set your sag..it just preloads the spring so that won't really do anything if you're bottoming.

More compression is the way to go if you're bottoming out under hard bumps/braking, etc.

If you're pretty heavy, you'll never get everything right particularly the sag, so you should probably get the appropriate springs for your weight and have it re-valved/shimmed.

If you're not pretty heavy, then you may want to see if your fork seals are leaking in which case your fluid level is low which is probably why you're bottoming out. If you decrease the air gap, or increase the fluid level, this will prevent bottoming but too much and you can lock up the fork.

Pretty much this. To expand, pretty heavy for the f4i's front forks is about 125lbs, meaning you need new fork springs to keep from botteming out. I gopro'd on my side fairing at the track and it was enlightening to see how much the forks moved going down the strait at full throttle [meaning light front end load]. I was almost botteming out just shifting. Forget about braking [btw I am about 160lbs].

I weigh in at 160 lbs. As I mentioned in my OP, I need someplace to start before I start tearing things apart/modding and the OE settings seemed like a good place. I appreciate the advice so far, but it appears more appropriate for the second stage of consideration.

Stock is a good place to start yes. Just know that you won't stop the botteming out no matter what you do with the stock pieces on the bike.

change the fork oil out with 15wt maxima fork oil for better damping, and set the fork oil level 10mm higher than stock to prevent bottoming. problem solved.

Yeah, hard would be all the way clockwise and soft would be all the way counter-clockwise if you're trying to get your baseline setup. I would start by checking for leaks by the fork seals and if they look fine, set the preload as close as you can, bump the compression all the way up, put a zip tie on the fork (to see how much it's moving), and see if that works at all. If it does, start decreasing compression till you're happy and then make your rebound adjustment. That's probably the best you can do without actually getting some work done. There are tons of guides on the internet but keep in mind it's never gonna be perfect because the forks are setup for a lighter rider.

^I did the 15w Maxima thing, along with a stiffer spring (.95, I weigh 160-170+gear) but it is not recommended since cartridge forks shouldn't be using heavy oils and since it increases both rebound and compression. Fortunately the stock ss8 is a pretty heavy oil already so I went for it. I haven't been able to push the setup hard yet (Sunday hopefully), but on the street it's been 20x better. Better yet I just drained the fluid from the bottom and kept the forks on the bike...hardest part was getting the fluid level/air gap right.

I suppose raising the oil level would help prevent the bottoming and you would get increased dampening from the heavier fluid but I would not expect it to come out perfect. Still sometimes some fresh fluid does wonders, and for street riding, it might be the ticket.

But if you really wanna do it right, get a racetech kit, or send your forks out to someone awesome (racetech/traxxion), or to someone local, and have them reworked (resprung and revalved/ modify the stock valves/shim stack).

^ i suggested he use 15wt fork oil and a higher oil level if he wasn't changing internals. it's a whole other ballgame when you start changing springs/valves.

madman, since you replaced your spring with .95's, you *need* racetech valves (with 5wt oil) since the stock valves are too weak for that heavy spring rate. also i bet it was really hard to get your oil level right with the forks still on the bike...it only takes 15-30 minutes to take the forks off anyway.

stock SS8 is 10wt oil. 15wt adds just the right amount of damping to a stock setup. it won't make the stock valves compensate for a heavier spring though. raising the fork oil level about 10-15mm is a well-known trick to prevent bottoming...but take the forks off the bike for an accurate reading since every mm counts. you can't get an accurate level when the forks are angled while still on the bike.

so the OP's options are to try the aforementioned cheap fix that works quite well, or spend big bucks on a professional fork job.

I know you suggested to do that without any changes and it sounds like a good, simple trick to try. I did the same on my old Kawi with damping rod forks and it worked great. I think that could work well within reason (weight of the rider).

Sorry I shouldn't have commented on what I did to mine but hopefully I was clear that it's not the right way to do things. I reallllly don't want to hijack I just want to elaborate.

My argument is of course my actual experience since I did it anyway and it worked out great for me. Maybe I don't ride aggressive enough and I definitely haven't had the chance to really push the setup yet so I dunno, but on the street it works pretty damn good.

There have been people who just changed the spring and went with stock or lighter fluid and I heard a bunch of complaints about a springy ride. Judging from that, I have to say that this worked out much better. The ride is definitely not bouncy although it might be a *bit* too stiff. Who knows maybe it still needs a bit more rebound and a bit less compression (not achievable with the stock valves) but it's not bad on the street. No way it's as good as a revalve but maybe someone faster can ride mine this weekend and tell me what they think.

By the way I measured the oil in cc's and did it that way (very carefully, and making sure that all the oil was out). Then I double checked the gap by measuring from the low and high side of the oil level and took the average. Then I made sure they were both the same. Wasn't hard, just had to be super careful...and yes removing the forks is not that difficult but I didn't have the means at the time to lift up the front properly.