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Hi !

My dry clutch feels way too stiff for my taste (Hypermotard 1100 `09). It`s OK on in normal road conditions, but when the road gets rough or in slow speed hill climbing it`s really killing my hand. Previous owner has changed original parts to Rizoma pressure plate and new springs which maker i don`t know. There reads "Innovative components" in the caps but nothing else. Please tell me if someone regonizes them. I forgot to test are they stainless steel, but i will check that later and inform.
I really like more look of the powder coated (?) black springs than the originals so i would like to keep the black color.

Just wanted to ask how much do the springs affect to stiffness of the clutch lever ? Many people seem to prefer Barnetts springs as good quality and OEM feel ?

Thank you.
 

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Just wanted to ask how much do the springs affect to stiffness of the clutch lever ?
The amount of force developed between the clutch plates is controlled by the stiffness (lb./in) of and number of clutch springs, specifically by the amount of preload on these springs. When the clutch is fully engaged, the friction force developed between the plates needs to be greater than the engine’s applied torque to prevent slip.

The force required to pull the clutch lever is ultimately controlled by the engine's power output. A Ducati superbike with a maximum torque of 65 ft-lb. transmitted though its clutch needs to have around 430 lb. of preload in the clutch spring(s) to prevent the plates from slipping.

This means that the hydraulic pressure on a typical 28 mm slave cylinder needs to be about 425 psi to overcome the 430 lb. spring preload and disengage the clutch. The distance that the slave cylinder needs to move (the pushrod that in turn separates the plates) has to be at least the thickness of the 2 mm dished plate in the clutch pack — say 3 mm tops.
About 94 lb. of force is needed to be applied to a typical OEM 13 mm diameter master cylinder piston to create 425 psi of pressure in the incompressible hydraulic fluid that, in turn, moves the slave cylinder. For every one mm that the slave cylinder moves the pushrod, the OEM master cylinder has to move about 4.6 mm.

In order to apply the required 94 lb. of force to the clutch master cylinder piston, the clutch control lever needs to be pulled, and here's where the lever's mechanical advantage comes into play.

The human hand can't repeatedly (without fatigue) apply 94 lb. of force to the lever so the master cylinder lever is designed to provide a mechanical advantage—to amplify the hand's force. The OEM design for example provides between a 4:1 (two finger) to a 9:1 force reduction (end of lever). This means that you have to normally apply between 23 and 11 lb. respectively with your hand to release the clutch.

The lever's mechanical advantage has it's consequences, however. Instead of having to move the master cylinder only 9 mm to disengage the clutch 2 mm, the end of the clutch lever now has to move more than 75 mm. In a racing situation this is undesirable because longer level movement results in slower shifts. Consequently, there's aftermarket radial master cylinders offered that reduce this movement, but at the sacrifice of higher clutch pull forces.

However, on the street it's desirable to have a longer lever movement, since the longer lever travel makes it easier to launch the bike from a stop by increasing the range of the "friction zone."

That said, the most practical way to reduce the clutch lever pull force is to change the diameter of the slave cylinder. The force-reduction aftermarket slave cylinder replacements offer around a 20% reduction but at the penalty of needing a longer clutch lever pull to get full disengagement.

A straightforward way to reduce pull effort is to reduce the force pushing the plates together. One way is to change the stock springs to ones having a lower stiffness. Another way is to reduce the number of springs from six to four. This gives a one-third reduction in lever pull as well as a one-third reduction in friction force in the clutch. Depending on the particular bike’s torque output, you might get slippage, but reports from owners say this approach works fine.

At least for awhile ...

Keep in mind that the force between the plates is determined both by the number of springs and the spring preload. Since preload is determined by the stack height, as the clutch friction plates wear the overall stack height decreases and consequently the force between the plates decreases.

So, decreasing your clutch lever force by removing springs will work for a new clutch but as the plates wear you will begin to experience slippage (and accelerated plate wear) and it's likely that you'll have to put them back in to get full mileage out of your clutch. The best way to test for clutch plate slippage is to apply full throttle power in top gear.

PS. The aftermarket stainless clutch springs that I've seen have a stiffness of 67.5 pounds per inch.
 

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OMG! That’s got to be the most ridiculous reply to a simple question I’ve ever seen. :)

Simply because you are not likely to change anything else effecting the pull yes, the springs are entirely what makes your clutch lever hard to pull.

There are different size slave cylinders that can have a small effect but at the cost of increasing lever travel more than some people like.

Like Belter said, best way to lighten the clutch is to pull two springs directly across from each other. Like at 12:00 and 6:00. I’ve tried this on both my 100 hp Monster and 150hp 999 and neither had any slip problems with fairly new clutch packs.




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The no name aftermarket Stainless clutch springs in my SS made the pull slightly stiffer. Adjusting the lever to fit my hand gave me an easier pull, though maybe the effort required didn’t actually change. An Oberon slave on my Monster made that a bit easier but not a huge improvement. I never regarded either bike as having a strong clutch pull. Arthritis is my main issue, and adjustable levers give me more grip with my shorter fingers.
 

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I have yet to run across aftermarket dry clutch springs that were not a good 10-20% stiffer than oem, but they are pretty.

As belter mentioned pull two and see if the clutch can slip, I have many customers riding with 4 springs and no problems. Some combinations to get a lighter clutch pull .

1. revert to lighter clutch springs-oem

2. keep the stiffer aftermarket springs but remove two opposite each other.

3. use oem springs and remove two as with #2

4. Buy a larger aftermarket slave cylinder and lighten the pull but know you are separating the pack less.

5. buy a aftermarket slave and master so you have hydraulic power (and range) to lift the stiffer springs that you do NOT need except for the fact they are pretty.

There is no reason you can not paint/powder the lighter oem springs, and 4 stiffer aftermarket springs will probably be close in rate to between 5-6 oem springs. Only downside to running 4 that I can think of is that if you break one in a crash you might not be able to ride home. If you have 6 and break one you can usually remove the opposite and ride home. You have options.
 

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The amount of force developed between the clutch plates is controlled by the stiffness (lb./in) of and number of clutch springs, specifically by the amount of preload on these springs. When the clutch is fully engaged, the friction force developed between the plates needs to be greater than the engine’s applied torque to prevent slip.

The force required to pull the clutch lever is ultimately controlled by the engine's power output. A Ducati superbike with a maximum torque of 65 ft-lb. transmitted though its clutch needs to have around 430 lb. of preload in the clutch spring(s) to prevent the plates from slipping.

This means that the hydraulic pressure on a typical 28 mm slave cylinder needs to be about 425 psi to overcome the 430 lb. spring preload and disengage the clutch. The distance that the slave cylinder needs to move (the pushrod that in turn separates the plates) has to be at least the thickness of the 2 mm dished plate in the clutch pack — say 3 mm tops.
About 94 lb. of force is needed to be applied to a typical OEM 13 mm diameter master cylinder piston to create 425 psi of pressure in the incompressible hydraulic fluid that, in turn, moves the slave cylinder. For every one mm that the slave cylinder moves the pushrod, the OEM master cylinder has to move about 4.6 mm.

In order to apply the required 94 lb. of force to the clutch master cylinder piston, the clutch control lever needs to be pulled, and here's where the lever's mechanical advantage comes into play.

The human hand can't repeatedly (without fatigue) apply 94 lb. of force to the lever so the master cylinder lever is designed to provide a mechanical advantage—to amplify the hand's force. The OEM design for example provides between a 4:1 (two finger) to a 9:1 force reduction (end of lever). This means that you have to normally apply between 23 and 11 lb. respectively with your hand to release the clutch.

The lever's mechanical advantage has it's consequences, however. Instead of having to move the master cylinder only 9 mm to disengage the clutch 2 mm, the end of the clutch lever now has to move more than 75 mm. In a racing situation this is undesirable because longer level movement results in slower shifts. Consequently, there's aftermarket radial master cylinders offered that reduce this movement, but at the sacrifice of higher clutch pull forces.

However, on the street it's desirable to have a longer lever movement, since the longer lever travel makes it easier to launch the bike from a stop by increasing the range of the "friction zone."

That said, the most practical way to reduce the clutch lever pull force is to change the diameter of the slave cylinder. The force-reduction aftermarket slave cylinder replacements offer around a 20% reduction but at the penalty of needing a longer clutch lever pull to get full disengagement.

A straightforward way to reduce pull effort is to reduce the force pushing the plates together. One way is to change the stock springs to ones having a lower stiffness. Another way is to reduce the number of springs from six to four. This gives a one-third reduction in lever pull as well as a one-third reduction in friction force in the clutch. Depending on the particular bike’s torque output, you might get slippage, but reports from owners say this approach works fine.

At least for awhile ...

Keep in mind that the force between the plates is determined both by the number of springs and the spring preload. Since preload is determined by the stack height, as the clutch friction plates wear the overall stack height decreases and consequently the force between the plates decreases.

So, decreasing your clutch lever force by removing springs will work for a new clutch but as the plates wear you will begin to experience slippage (and accelerated plate wear) and it's likely that you'll have to put them back in to get full mileage out of your clutch. The best way to test for clutch plate slippage is to apply full throttle power in top gear.

PS. The aftermarket stainless clutch springs that I've seen have a stiffness of 67.5 pounds per inch.
This has got to be the Response of the Day Award Winner! Just awesome! Well done sir! :)
 

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I have yet to run across aftermarket dry clutch springs that were not a good 10-20% stiffer than oem, but they are pretty.

As belter mentioned pull two and see if the clutch can slip, I have many customers riding with 4 springs and no problems. Some combinations to get a lighter clutch pull .

1. revert to lighter clutch springs-oem

2. keep the stiffer aftermarket springs but remove two opposite each other.
Two weeks ago I removed two from my new Ducabike clutch after Ducvet's suggested it to me.

Amazing - I now have a clutch that is slightly stiffer than other non-Duc brands.
No problem with slippage.
Not that I plan to crash, but could keep the spare two under the seat.
 

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You’re better off just keeping your phone charged. If you crash hard enough to ruin a clutch spring I doubt you’ll be riding it home anyway.
 

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i rode a 1098 once that had two posts broken off so the only spring pattern that allowed equal load across the plate was 3 springs. it might slip if you really pinned, but i was amazed how much it didn't slip.
 

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Discussion Starter #11
I have yet to run across aftermarket dry clutch springs that were not a good 10-20% stiffer than oem, but they are pretty.

As belter mentioned pull two and see if the clutch can slip, I have many customers riding with 4 springs and no problems. Some combinations to get a lighter clutch pull .

1. revert to lighter clutch springs-oem

2. keep the stiffer aftermarket springs but remove two opposite each other.

3. use oem springs and remove two as with #2

4. Buy a larger aftermarket slave cylinder and lighten the pull but know you are separating the pack less.

5. buy a aftermarket slave and master so you have hydraulic power (and range) to lift the stiffer springs that you do NOT need except for the fact they are pretty.

There is no reason you can not paint/powder the lighter oem springs, and 4 stiffer aftermarket springs will probably be close in rate to between 5-6 oem springs. Only downside to running 4 that I can think of is that if you break one in a crash you might not be able to ride home. If you have 6 and break one you can usually remove the opposite and ride home. You have options.
Good list. Thanks for that. I thought about spraying the OEM springs, but i doubt regular paints won`t last long. I don`t have possibility to powder coat them, so i just use spray can or paint gun. Propably spray them because i don`t want to buy special paint and flex addon for so small project.

Forgot to mention that i currently have short levers. Previous owner had changed them (they look www.the2wheels.com levers). I will change them back to originals when i found black ones. This came with silver levers from factory.

Good advices from all of you, thank you. And Stregas reply was...pretty amazing :D
 

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If you crash hard enough to ruin a clutch spring I doubt you’ll be riding it home anyway.
Not always. early clutch covers were a nice thick cast aluminum so they took a fair bit of abuse without any clutch damage. The later version (late 90's) became a sheet metal stamping that would easily dent in a tip over and if the clutch was spinning under the cover (or if you started it with the dent) you are likely to break an inner clutch hub post. Likewise for the cool kids who mounted carbon fiber covers, they look good and would keep your toes out of the clutch but had little to no protection for a clutch part.

To this day my #1 addition to most of my Ducati dry clutches is a thick billet clutch cover to protect whats underneath. Well except my street monster that might as well not have a cover, it has some titanium tubing 1/2 cover that is sexy but will cost me money some day.
 

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That’s exactly why I switched out my pretty little CF cover to this for track riding.




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Woodcraft is good stuff!

My only nitpick with them is that they copied the dimensions of the cover from the later version stamped steel cover. You know the one that used a rubber sound deadening gasket that quiets the clutch noise? On an open clutch cover :confused: So if you remove the sound deadening gasket on your open clutch cover be sure to pick out the 4 brass spacers in the gasket or your clutch cover will likely hit the clutch springs.

If they had copied the earlier cover there would be no need for spacers. I think I dislike it more when great companies do silly things and when they know it and do not fix the design flaw. and for the record they are one of my favorites to deal with.

I will add I do not mind shorty brake levers as long as they are quality and not "cheap" but I have a real distaste for shorty clutch levers as I find the loss of length an issue I don't like two finger clutch levers and Ducati's. fixing that may be all you need. I have found rattle can paint holds up just fine on clutch springs and if it wears away every few years you can touch it up in minutes.
 

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I leave the gasket on only because the paint underneath is totally messed up from years of having it there.

My beef with all the covers is how much they stick out even without the gasket. There’s almost a 1/2” of excess clearance.


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