wilbers fork springs/fork stiction???

[Ramblin Man]

Since I put in my wilbers fork springs, it seems like the forks have more stiction than before. I went from a set of 04 springs to the wilbers, and from 12.5 weight oil to 7.5.

I thought that maybe I had reinstalled the my superbrace incorrectly but I removed and retorqued it and it didn't change.

I have the preload cranked all the way out. I have my compression damping almost all the way out also.

Overall the ride is great, and the forks work well over the larger ripples and bumps, but on the smaller bumps the handlebars follow the road contours instead of the front wheel, if you get my meaning.

Its almost as if the weight of the oil is too high, and maybe it is, but it was the recommended weight by wilbers and half the weight that was in there.

Just wondering if anyone experienced anything like this. I'm a big guy so I wouldn't think I would be suffering from this type of problem.

 

[UberKul]

I felt that also and can only attribute it to the new springs offering more resistance at the beginning of compression stroke. Remember we did have to compress them just to get the nut started. The best thing I did setting up the forks after the spring install was crank in a few more clicks of rebound. FWIW.

 

[twowheelnut]

RM, call Klaus. I have nothing but happy happy, joy joy. 7.5 weight and all (manufacturer specs not withstanding, of course).

 

[dobias]

Ramblin Man,

Unless your 12.5w & the 7.5w oils are the same brand, you're just kidding yourself with any comparison. True viscosity (measured in stokes) doesn't have any relationship to the "weight" shown on the fork oils.

The actual Wilbers 7.5w oil is an unpublished viscosity so there's really no way to compare it with any other brands. When asked what viscosity his 7.5w oil was he would only say, "try it you'll like it."

dobias :glare:

 

[Geezer]

Fork Oil Comparison Table

I used Silkolene RSF 2.5, which is very close to the Yamaha 7.5 that came from the factory. I did adjust the damping a few clicks over the course of several rides. I have no complaints.

 

[twowheelnut]

Fork Oil Comparison Table
I used Silkolene RSF 2.5, which is very close to the Yamaha 7.5 that came from the factory. I did adjust the damping a few clicks over the course of several rides. I have no complaints.

Kayaba's oil, though not labeled as such, is closer to '5' in their speak, according to one of their stateside racing engineers spoke to last year, FWIW.

 

[UberKul]

Fork Oil Comparison Table

Very handy!

Makes me think the Bel-Ray 7wt I used is a little heavy. No clue of the operating temps inside the forks but mine definitely feels better after riding a while.

 

[Ramblin Man]

I've only used bel-ray in the FJR. I've mixed though. I had 12.5 which was really equal parts of 15 and 10 weight oils, and this time around I mixed 10 and 5 to get 7.5.

So Wilbers was recommending "their" 7.5 weight oil huh? I've only got two more clicks to go and I'm all the way out. I may just be over sensitive.

I guess I can always get the mighty vac out and remove measured quantities of oil from each tube and replace it with straight 5 weight to see if that helps.

Maybe I should pull the caps and replace them in an effort to reduce the amount of air in the tubes. Overall I'm happy with the springs. It just they're a little stiff. Maybe I just need to give it another couple weeks.

 

[dobias]

IMHO either Bel Ray 3w (11.0 t@40C) or Bel Ray 5w (17.1 cSt@40C) would provide a close match to Yamaha's #01 fork oil they rate as 10w (15.6 cSt@40C). I used Silkolene 2 1/2w (13.6 cSt@40C) for that reason & I'm happy with the range of adjustments.

dobias :glare:

 

[jestal]

One other thing that you might try is to decrease the rebound damping setting and see if that helps.

The Wilbers springs are very progressive and pretty soft for the first bit of travel...at least the ones I got were that way.

If you have too much rebound damping dialed in the fork and "pump down" and not recover on the small bumps so that it seems to be hard or have a lot of stiction as you describe.

"Pump down" is common with too much rebound damping for the given (effective) spring rate. Pump down is a phenomenon where the fork compresses over a bump and, due to excessive rebound damping, it cannot return to the original position before the next bump comes along. This condition gets worse and worse as the fork cannot extend on rebound rapidly enough before the next bump comes along. You might have the rebound set OK for the heavier rate of the spring that you get into on bigger bumps but that same setting is too much for the light weight part of the travel (those small bumps you mention). That is another problem with variable pitch springs and another reason that I did not like them and used a straight rate spring from RaceTech instead of the Wilbers. Tried the Wilbers and didn't like them.

The top black knob on the fork tubes is the rebound damping adjustment. Screw them in (tighten) gently until they bottom and back out about 10 clicks. Ride it and see if your problems persist. Then back them out another 10 clicks and see if the problem gets better. You want to make a significant change from the 10 turn baseline to see if this is the problem and if reducing rebound damping will help. If it works OK at 20 clicks out then start adding rebound damping by tightening 1 click at a time to see where the rebound damping becomes critical for pump down and back off a click or two.

This could also be brought on by the softer initial rate variable pitch Wilbers springs combined with too high a viscosity fork oil. Even if the fork oil is a bit too heavy you should be able to get rid of enough rebound damping to see if the problem is pump down and see if you can improve on it by dailing out preload as an experiment. If you end up having to go 20 clicks out on rebound to make the situation better then I would go to a lighter fork oil to get back into the normal range of adjustment.

 

[Ronman]

It could be your forks are binding from not being aligned. Before changing anything, I'd ask if you made sure everything was aligned before tightening the triple clamp, fork brace and axle pinch bolt?

I'll tighten just one of the lower triple clamp pinch bolts on each leg, (I'll tighten the top pinch bolt first on my dirt bike, but I think the FJR is probably too heavy to be supported by the upper clamp) then brace the front tire against a wall while compresing the forks several times. I'll then tighten the upper triple clamp bolts and remaining lower triple clamp bolts, leaving the axle pinch bolt loose. Bounce it a few more times, then tighten the axle pinch bolt. It's okay to have the axle tightened before starting this procedure, but remember to tighten the pinch bolt last.

 

[dobias]

I have to add a big "Amen" to Jestal's advice about fork rebound pump down. I found that was a big part of my problem with the (HID) headlights bouncing &/or jiggling. It brought out the worst in cagers I happened to follow on two lanes even though I gave them distance.

I had to back off the rebound from several clicks out to 15 clicks out and also reduced the tire pressure from 42 to 36 lbs. The headlights are very steady now.

I just put on a few hundred miles to make certain, but, I'm surprised by the big reduction (if not elimination) of my hands going to sleep! Yes, the "carbs" were synchronized this spring but I was still contemplating the last resort of bar end weights. I'm convinced the forks adjustment made that much of a change in vibration.

I have Wilbers springs and Silkolene 2 1/2w fork oil.

dobias :glare: