Busy front end after spring change

[KennyWiz]

I recently had the the springs changed all around on the bike and upgraded to a Wilburs in the rear. I resprung the rear with a 330lb spring from wilburs and 1.2kg (300lb ish) in the front. The front springs came with two pvc tubes precut. I had the forks done at a shop as I am not familiar with their dis-assembly. 5wt oil was used.

When I got the bike back I was quite happy. Guess anything other than what was on it was a vast improvement. Now I am noticing the front end is VERY "busy" at high speeds (above 70-80mph). I notice less with my wife on but I also don't ride as aggressive with her.

I've read other posts and thought it may be too much preload. The springs match my weight per the RT calculator and also match what I have in the rear. I asked the mechanic today and he said the PVC tubes did not put any preload on the springs.

I've played with the front settings and no fix. My current settings are:

Preload 5 lines showing.

Compression 5 out from full open (much higher spring rate, less compression needed)

Rebound 5 out from full closed

Any suggestions?

Thanks for your time.

 

[azitlies]

I recently had the the springs changed all around on the bike and upgraded to a Wilburs in the rear. I resprung the rear with a 330lb spring from wilburs and 1.2kg (300lb ish) in the front. The front springs came with two pvc tubes precut. I had the forks done at a shop as I am not familiar with their dis-assembly. 5wt oil was used.

When I got the bike back I was quite happy. Guess anything other than what was on it was a vast improvement. Now I am noticing the front end is VERY "busy" at high speeds (above 70-80mph). I notice less with my wife on but I also don't ride as aggressive with her.

I've read other posts and thought it may be too much preload. The springs match my weight per the RT calculator and also match what I have in the rear. I asked the mechanic today and he said the PVC tubes did not put any preload on the springs.

I've played with the front settings and no fix. My current settings are:

Preload 5 lines showing.

Compression 5 out from full open (much higher spring rate, less compression needed)

Rebound 5 out from full closed

Any suggestions?

Thanks for your time.

Ken when I changed out my springs on the ST1300, used sonic springs 1.2 kg.

From your description, the comment by the mechanic would worry me. In my case, the pvc tubes needed to be cut so the *entire* (overall) length (of spring, washers and pvc) matched what was the original length of the same components. It *sounds* like they may not have done that in your case...

Also, the fluid has to be the correct height (amount). It's hard to know what's going on without having it apart, but it sounds as though it's acting squirrely? As in not solid and planted? you say at high speeds, is it normal at lower speeds?

I'd still want to know why the mechanic would say the pvc lengths put not preload on the springs... that's bizarre.

 

[Bustanut joker]

Sure sounds like a preload issue.

Paging Jeff Ashe.. er, one of dem fart schmuckers here.

 

[KennyWiz]

I recently had the the springs changed all around on the bike and upgraded to a Wilburs in the rear. I resprung the rear with a 330lb spring from wilburs and 1.2kg (300lb ish) in the front. The front springs came with two pvc tubes precut. I had the forks done at a shop as I am not familiar with their dis-assembly. 5wt oil was used.

When I got the bike back I was quite happy. Guess anything other than what was on it was a vast improvement. Now I am noticing the front end is VERY "busy" at high speeds (above 70-80mph). I notice less with my wife on but I also don't ride as aggressive with her.

I've read other posts and thought it may be too much preload. The springs match my weight per the RT calculator and also match what I have in the rear. I asked the mechanic today and he said the PVC tubes did not put any preload on the springs.

I've played with the front settings and no fix. My current settings are:

Preload 5 lines showing.

Compression 5 out from full open (much higher spring rate, less compression needed)

Rebound 5 out from full closed

Any suggestions?

Thanks for your time.

Ken when I changed out my springs on the ST1300, used sonic springs 1.2 kg.

From your description, the comment by the mechanic would worry me. In my case, the pvc tubes needed to be cut so the *entire* (overall) length (of spring, washers and pvc) matched what was the original length of the same components. It *sounds* like they may not have done that in your case...

Also, the fluid has to be the correct height (amount). It's hard to know what's going on without having it apart, but it sounds as though it's acting squirrely? As in not solid and planted? you say at high speeds, is it normal at lower speeds?

I'd still want to know why the mechanic would say the pvc lengths put not preload on the springs... that's bizarre.

light and not planted, yes

Requested fluid set to 110mm as recommended by RT

The mechanic said he needed the PVC to match the OEM length but said it did not add preload. I was skeptical too.

I appreciate any help to get this locked onto as a preload issue. The mechanic said he would be happy to work with my if I could isolate the issue. (seems like its his issue not mine, but anyway).

What should the OAL be if this is the case?

Thanks

 

[SkooterG]

1.2 lbs springs on the forks is definitely on the stiffer side. But you must be incorrect that you only have a 330 lb spring on the shock. I have never heard of one that low.

Not sure what you mean by 'busy'.

 

[Constant Mesh]

The 2003 Service Manual lists 100 mm for the oil level. Maybe an aftermarket spring changes the recommended level.

One might speculate that dialing in a bit more rebound than normal might be recommended for a stronger spring (slow the extension of the fork tube).

 

[azitlies]

light and not planted, yes

Requested fluid set to 110mm as recommended by RT

The mechanic said he needed the PVC to match the OEM length but said it did not add preload. I was skeptical too.

I appreciate any help to get this locked onto as a preload issue. The mechanic said he would be happy to work with my if I could isolate the issue. (seems like its his issue not mine, but anyway).

What should the OAL be if this is the case?

Thanks

See, now that's wrong, I don't think the replacement springs are the same length as the oem springs. Why he would say he needed the pvc lengths to be the same is ... it could only be if the springs were the same length...

that's not making sense.

 

[KennyWiz]

1.2 lbs springs on the forks is definitely on the stiffer side. But you must be incorrect that you only have a 330 lb spring on the shock. I have never heard of one that low.

Not sure what you mean by 'busy'.

Ah yes! It's set for a 330lb rider with gear, sorry. Not sure of the exact rate but they are as close to a match as I could get.

Busy:

The front end moves around alot and high speed. Does not feel planted. Light.

 

[r1byker]

As an experiment, just try lessening the pre-load and see what it does. Keep track of what your doing (as in, write it down) so you can go back to it as your baseline. If it feels better, then you know you're on the right track. If not, go back to baseline and then go the other way. Of course, the ideal thing to do is to set the sag.

 

[KennyWiz]

As an experiment, just try lessening the pre-load and see what it does. Keep track of what your doing (as in, write it down) so you can go back to it as your baseline. If it feels better, then you know you're on the right track. If not, go back to baseline and then go the other way. Of course, the ideal thing to do is to set the sag.

Preload is already all the way out.

Current setting listed in 1st post.

Thanks!

 

[Queensland Ken]

Hi,

I would tend to think 5wt oil would be a bit light.

When I did my forks, I replaced it with 10, better compression & rebound.

As mentioned in prior posts, record everything.

Cheers

 

[Fred W]

This should not be a preload issue. All that the preload really does is to modify the nominal ride height (dynamic sag). In other words, where in the range of the shock/fork the suspension will operate. For example, if the preload was too high you would be running at too high of a ride height, possibly allowing the fork to "top out" on rebound. It would also effect the steering geometry by varying the front height, but that is not germane to this discussion.

You say that the suspension is "busy" at higher speeds. That probably means that the dampening is not properly matched to the new spring rate and weight load. As you probably know, (low speed) dampening is varied by adjusting some orifices via the top and bottom clickers of the fork. One for compression (bottom) and one for rebound (top). These orifices are open the most, and provide the least dampening, when the clickers are turned fully CCW. Conversely, you can increase dampening by closing down the orifices, by clicking in a CW direction (easiest to remember, righty tighty). In general, a stiffer spring should require less compression dampening (because the heavier spring is fighting fork compression more on its own) but increased rebound dampening (to keep that hefty spring under control).

I would suggest that your busy feeling is caused by excessive (especially high speed ) compression dampening. When you hit a sharp, quick road variation, the suspension is not allowed to absorb the impact because it is overdamped. Try backing off the compression dampening significantly (too much) and feel if the busy ness changes.

The size of the orifice is only one part of the equation. The other significant part being what weight of oil that you are trying to jam through those the little holes. You mention the shop stuck in 5 weight oil, but which one? Not all 5 weight oils are the same, or even close, in viscosity. If the oil is considerably heavier, then that along with the stiffer spring means that your high speed compression dampening may be way too high.

Unfortunately, the clickers adjust primarily the low speed dampening with some carry over into the high speed. What this ultimately means is that you may end up having to change the viscosity of your fork oil to achieve both the high and low speed dampening that you need.

I would tend to think 5wt oil would be a bit light.

When I did my forks, I replaced it with 10, better compression & rebound.

Just as a point of reference, the stock Yamaha fork oil is generally considered to be a 3 weight oil. But as I mentioned, none of the oil purveyors seem to be able to agree on what "weight" means. In any case, the Yamaha fork oil is very light viscosity.

A true 10 weight oil would be far too viscous for the stock orifices in a Yamaha fork. You would not be able to open the clickers far enough. But some company's 10 weight could be as thin as a 3 weight. That's why it is important to know what the actual viscosity of the oil you are using is, not the "weight" rating.

Here's my favorite fork oil viscosity chart. Look yours up and compare it to Yamaha 01 Fork oil (hint... it's way down at the bottom)

 

[ahchiu]

I have the Hyperpro setup and they call for the front to be PRELOAD 3 lines showing, COMPRESSION 15 clicks open +/- 4(counter clockwise), REBOUND 6 clicks open +/-2, I have my preload with no line showing and that put my sag @ 35mm

 

[Bustanut joker]

Good explanation Fred.. I was assuming by busy he was indicating something like the forks "topping out" while on the upstroke.

 

[KennyWiz]

This should not be a preload issue. All that the preload really does is to modify the nominal ride height (dynamic sag). In other words, where in the range of the shock/fork the suspension will operate. For example, if the preload was too high you would be running at too high of a ride height, possibly allowing the fork to "top out" on rebound. It would also effect the steering geometry by varying the front height, but that is not germane to this discussion.

You say that the suspension is "busy" at higher speeds. That probably means that the dampening is not properly matched to the new spring rate and weight load. As you probably know, (low speed) dampening is varied by adjusting some orifices via the top and bottom clickers of the fork. One for compression (bottom) and one for rebound (top). These orifices are open the most, and provide the least dampening, when the clickers are turned fully CCW. Conversely, you can increase dampening by closing down the orifices, by clicking in a CW direction (easiest to remember, righty tighty). In general, a stiffer spring should require less compression dampening (because the heavier spring is fighting fork compression more on its own) but increased rebound dampening (to keep that hefty spring under control).

I would suggest that your busy feeling is caused by excessive (especially high speed ) compression dampening. When you hit a sharp, quick road variation, the suspension is not allowed to absorb the impact because it is overdamped. Try backing off the compression dampening significantly (too much) and feel if the busy ness changes.

The size of the orifice is only one part of the equation. The other significant part being what weight of oil that you are trying to jam through those the little holes. You mention the shop stuck in 5 weight oil, but which one? Not all 5 weight oils are the same, or even close, in viscosity. If the oil is considerably heavier, then that along with the stiffer spring means that your high speed compression dampening may be way too high.

Unfortunately, the clickers adjust primarily the low speed dampening with some carry over into the high speed. What this ultimately means is that you may end up having to change the viscosity of your fork oil to achieve both the high and low speed dampening that you need.

I would tend to think 5wt oil would be a bit light.

When I did my forks, I replaced it with 10, better compression & rebound.

Just as a point of reference, the stock Yamaha fork oil is generally considered to be a 3 weight oil. But as I mentioned, none of the oil purveyors seem to be able to agree on what "weight" means. In any case, the Yamaha fork oil is very light viscosity.

A true 10 weight oil would be far too viscous for the stock orifices in a Yamaha fork. You would not be able to open the clickers far enough. But some company's 10 weight could be as thin as a 3 weight. That's why it is important to know what the actual viscosity of the oil you are using is, not the "weight" rating.

Here's my favorite fork oil viscosity chart. Look yours up and compare it to Yamaha 01 Fork oil (hint... it's way down at the bottom)

Compression is set at 5 clicks from full open

Rebound is set 5 clicks from full closed

(Listed in 1st post)

Fork oil used was Maxima Racing Fork Fluid (85/150, 5wt)chart shows slightly heavier than stock Yamaha

I understand I would have some issues after such a drastic spring increase. I'm just worried about the pvc "spacers" adding preload to a setup that was ordered to be neutral just springs alone.

I can use different oil but if I am not certain of the spring setup, the oil change may be moot.

Called RT and they were no help. They said the PVC spacers can be cut to length to achieve the "correct preload". I noted my issue and was told to try cutting. I requested a proper length and was told to cut a little off each time until the proper feeling was achieved.

Really? There HAS TO BE a measurement out there, right? I'm gonna go broke having the tech take the forks off and apart multiple times. My tech told me the pvc spacers were necessary to the install?

 

[superfuzz]

I'm not going to pretend to be a suspension tech (actually probably know just enough to screw everything up)but I can tell you about my experience with what sounds like similar fork symptoms.

Many moons ago, I had (what turned out to be) an incompetent mechanic install stiffer Race Tech springs in my Superhawk. When I got it back, the handling felt ***-low for lack of a better description; like I was riding with a passenger all the time. Didn't feel at all planted. Tried ajusting the sag but couldn't get enough even with the adjusters all the way out.

To skip to the end of my story, the spacers were too long and even with the preload adjusted to zero (all lines showing, all the way out, whatever) the fork was riding too high in the stroke.

A different mechanic cut the spacers, IIRC to match the RT spring lenth+spacer to match the overall length of the stock spring, and that solved the problem. I was able to actually use the preload adjusters to get the correct amount of sag and the forks felt great.

My guess is that someone screwed up the spacer length.

 

[azitlies]

These things seem to become overly complicated waaaaaaaaaay too fast...

everyone wants to help, which is good, but me thinks you need to start with the basics, before moving to the secondary stuff.

Like Superfuzz suggests also, I'd start with the installation the tech did. He keeps on saying things that just don't sound quite right to me... So, he says he cut the spacer to the same length as the original spacer... You need to ask him why? You need to have a conversation with him and try to verify that the overall length of what went in was the same as what came out (spacer, spring and any washers).

Because you didn't do the actual work, it may be difficult to communicate with him. But what you need to know "did he cut the spacer so that the entire length matches up with the original entire length". That's how you measure how to cut the spacer, if done properly. There's no other way. If he can't answer that question, he probably doesn't know what he's doing.

The next thing I'd checking, assuming the above is correct, is the type of and amount of fluid. Again, you didn't do the work so you'll have to enlist the help of your tech. But do some research, know what yer talking about, then ask him intelligent questions, to find the answer.

AFTER you determine the answer to the above two questions, then get all involved in the clicks from in, clicks from out, orifices, viscosity, etc etc. If the tech didn't assemble it properly, none of this stuff is going to matter...

 

[HaulinAshe]

These things seem to become overly complicated waaaaaaaaaay too fast...

everyone wants to help, which is good, but me thinks you need to start with the basics, before moving to the secondary stuff.

Ding Ding Ding... We have a winner!!!

Start with the basics, go back to the basics. All the discussion about fluid weights, clicker settings etc. is irrelevant to spring rates. ALL suspension starts with spring rates. You cannot assume that the rear springs are for a "330-lb rider". Someone may have screwed up and installed the wrong spring. Incorrectly springing a Sport-Touring bike is the most common mistake made. Most of the formulas/charts/calculations used for everything else go out the window for S-T. S-T requires a delicate balance of performance and comfort that often requires re-springing to get it just right for a particular rider.

So... what I'm trying to say and taking too much time to get there is...

We know your front springs are 1.2 kg/mm (which is stiff for an FJR). What is the rear spring rate? It should be marked somewhere and should be in the 130-170 N/mm or 850-1,100 lb/in range. Look for similar numbers or some part number that can be referenced.

Then get back to me. I'll do my best to help you.

 

[HaulinAshe]

I've played with the front settings and no fix. My current settings are:

Preload 5 lines showing.

Compression 5 out from full open (much higher spring rate, less compression needed)

Rebound 5 out from full closed

Any suggestions?

Understand that despite what the manual implies, the "lines showing" is merely called preload. It actually does NOT effect fork spring preload, but is instead a ride height adjuster. In that regard, it has the same typical effect on steering sensitivity as a true preload, which is probably why Yami decided to refer to it as such.

Front Fork Spring Preload on an FJR fork is set entirely by the spacer tube lengths used above the fork springs. The stock configuration provides for roughly 11.0mm of spring preload which is actually applied as the fork caps are screwed into place. With the caps removed, the "assembly" will have a couple millimeters of "play", causing the entire assembly to compress or preload approximately 11.0 mm during final assembly.

Substantial/excessive front fork spring preload (spacers + springs) too long, can result in a harsh ride feeling, especially at the top of the stroke where movements are quick and small. I assume that to be the "busy" feeling you are expressing. But I tend to do well with the *** in assume.

The fact that you have both compression and rebound set to 5-clicks, tells me that you may be looking for something that isn't going to be there. Those clickers don't allow the stock valving to function reliably below 6-clicks. Your re-spring should have resulted in a starting clicker setting(s) of 10-15 clicks.

There is a problem getting sufficient fork rebound damping using the recommended oil weight with non-OEM/stiffer fork springs. That's why anytime someone clearly requires 1.2 kg/mm fork springs on an FJR, I insist on re-valving the cartridges. Using heavier weight fork oil will work, but that solution also increases the harshness of the ride up top (slab riding etc.). Works great in the twisties and/or when two-up and loaded, but totally sucks when solo or slabbing it for hours.

I really need to give up typing so much!!!