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All clutches in the Sigma Performance Competition Slipper Clutch range are delivered with settings that, with a fresh set of clutch plates, will give a reliable and efficient slipper clutch action. Our very first British Championship Supersport victory with Jay Vincent at Brands Hatch in April 2004 used the 'as delivered' settings.
As standard our clutches are lighter and smoother in operation than the OEM clutches fitted to some sports bikes. Our clutches typically weigh around 1 kilo against about 1.5 kilo’s for the OEM slipper items.. so as standard you have quicker throttle response, a smoother and more accurate shifting action and as a result of a ball bearing equipped ramp system and more track sensitive ramp angles you get a much smoother action.
For major changes in feel different ramp angles are required, on several clutches in the range we can supply different angle ramps but these tend only to be for bikes where we feel there is a need for different designs. That doesn't mean you shouldn't try something a little different though. Slipper clutches work by the back torque from the rear wheel forcing the centre of the clutch to rise up its ramps, this in turn pushes the pressure plate off the top of the pack. The more violent the back torque (for very violent think three full racing downshifts and no clutch) the further the centre rises. Once the clutch pack has broken (ie the plates are not clamped hard together any more and the clutch is slipping, the centre stops rising, indeed it starts to fall..as it falls the clutch re-engages, as soon as it does it is driven back up the ramps, starting the cycle again. An equilibrium point is quickly reached.
So lets consider the situation, all our clutches are designed to have a 1mm centre to pressure plate clearance with a fresh clutch pack, what happens if we reduce that distance? Well the clutch works earlier that's what.. When the clearance is set at 1mm there will be a few occasions where a small amount of back torque isn't enough to allow the clutch centre to travel right up the its stroke. If we reduce the thickness of the pack, which brings the pressure plate closer to the centre, then the clutch will work when previously there was not enough back torque to make it work. Where it was always going to work anyway, now it will work earlier, that translates into further before the corner and with less engine braking..…
Adjusting the clearance is quite simple, just remove one of the metal plates and replace it with a thinner one, checking the operating clearance as set out in the CD that came with your clutch. (Care; on Suzuki’s only don’t forget to readjust the pushrod clutch adjustment next to the front sprocket to a minimum of 0.5-0.8mm slop every time the clutch pack is thinned, do not assume that adjusting the cable at the handle bar will do).
It is possible to run the clearance right down at 0.4mm, but bear in mind heat build-up will change some clearances, and because the clutch is working more it might wear the plates more so the tighter the clearance the more regular checking needs to be done. It goes with out saying that if you have your clutch set at 0.4mm and heat closes the gap by 0.2mm mid race then wear of just 0.2mm will result in clutch slip. Race over…
So, at 0.4mm the clutch will work pretty much as soon as you shut the throttle, and whenever you shut the throttle. At 1.0mm it will work slightly less often and will not work for small amounts of engine braking. All of these clearances change as the friction plates wear, and they can only be adjusted by different pack thicknesses, with Suzuki and Honda clutches we can move things by 0.3mm jumps, on the less subtle twins we can only move them by 0.5mm jumps, and that's close enough.
A rider will feel the difference between 1.5mm and 0.6mm but the difference between 0.8mm and 0,6mm is going to be as miniscule as the measurement!! Remember we don't want a clutch that feels different too easily or normal wear will cause problems. In most case the best friction plates are the standard ones, they appear to take the additional loads placed on them by a slipper clutch in their stride.
A second adjustment is to change the strength of the main clutch springs. The stronger the spring rate the harder the clutch centre has to work to hold the clutch disengaged. The effect is to transmit more engine braking through, BUT it gives the plates a much harder time. You do not have to change all the springs; you can say have 2 stiff ones and 3 (or 4 depending on the clutch) a weaker ones.. just make sure the stiffer springs are distributed opposite each other to equalise the effect. If you do deliberately increase the spring rate for this effect you must monitor pack wear more closely.
Some times major increases in power mean stiffer springs are need to stop slippage going forward. Things will work far better if the increase in spring rate is just sufficient to handle the extra power. For some bikes we have built clutches with different angle ramps to ensure that stiffer springs do not affect the gentle slip action we prefer.
Lets have a look at the latest info we have on the various clutches we sell, and remember they are all designed to function just fine with a new original clutch pack, if you insist on experimentation these numbers are intended to provide a little guidance.
And before you start playing too much, remember that we believe the standard numbers, a 1 to 1.2 mm clearance (1.5mm on Ducati’s and other big twins) will do just fine for most riders in most situations.
All these comments should be read in conjunction with the fitting instructions included with your clutch.
Clutch set up info:
>Ducati
>Ducati 48 tooth
>Ducati 848 / Sport Classic / Multistrada / ST3 / ST4 (all big wet clutch models)
>Aprilia 450/550
>Honda SP - 1/2
>Honda CBR1000RR (2004/2005)
>Honda CBR600RR
(2006 and on)
>Honda CBR929/954 (2000 - 2004) (SC50)
>Honda CBR600RR (up to and including 2006)
>Honda CBR600RR (2007 on)
>Honda CBR600RR (2007 Evo Corsa on)
>MV Agusta 1000
>Suzuki Hayabusa
>Suzuki GSXR1000 (K1-K4)
>Suzuki GSXR1000 (K5 and on)
>Suzuki GSXR 600/750 (K1-K5 inclusive)
>Suzuki GSXR 600/750 (K6 and on)
>Yamaha R1 (pre 04)
>Yamaha R1 (2004/2005)
>Yamaha R1 (2006)
>Yamaha R1 (2007 and on)
>Yamaha R6 (up to and incl. 2005)
>Yamaha R6 (2006 on)
>Accessories
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Ducati
All bikes with air-cooled clutches since 1990. Six ramp, dry type. Hard anodised in grey with a Red pressure plate using a ceramic friction surface; Uses standard clutch plates and springs. Includes both Clutch centre and Alloy basket
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Ducati make several different types of clutch plate, original fibre and steel; aluminium forging and steel and two types of sintered plate, small O/D and Big O/D. There are three types of metal plate too. 1.5mm plain; 1.5mm bowed and 2.0mm plain.
Sintered plates are used on really high horsepower stuff. Anything under 130 bhp can use the steel or aluminium plates. The aluminium plates are brilliant and light, they don't damage the baskets as much and reduce the flywheel effect; and as they cost the same as the old steel set they are a bargain.
The big O/D and little O/D sintered plates are the high horsepower jobbies. The little O/D versions are the street SPS plates and the big O/D versions are a lighter version historically used on
factory and customer race bikes for racing. We can supply any of the types (I knew I had been in this Ducati game too long!!).
The clutches work fine at a clutch centre to clutch pressure plate clearance of 1.5mm, 1.0mm is as low as you will ever need to go, the pulses from a big vee twin are pretty unsubtle so the delicacies of a really small clutch centre to pressure plate measurement are not needed. Only 1.5mm and 2mm metal plates are available so any change will be in 0.5mm jumps. Used in conjunction with a combination of worn and new friction plates very accurate clutch clearances can be achieved.
Ducati's will occasionally judder away from a stop though (those same big pulses jerking everything around). Standard packs of plates include 1 bent /warped 1.5mm plate in their assembly. This needs to be in the centre of the pack. (you can spot the bowed plate by putting the metal plates on a flat surface and finding the one(s) that are bowed).
If you have 'off the line' judder try one or more of these plates, keep them in the centre of the pack and where you can arrange them so the bent sides point at each other, make sure they don't all point he same way as this just messes up the pressure plates. The bent shape damps some of the shock of the clutch going together; unfortunately they also create a little drag so the plates can wear more, still if you have a problem it is a solution.
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Ducati. 48 tooth
All bikes with air-cooled clutches since 1990. Six ramp, dry type. Hard anodised in grey with a Red pressure plate using a ceramic friction
surface; Uses standard clutch plates and springs. Includes Clutch centre, 48 tooth Alloy basket and plate set.
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These clutches come with their own 48T tooth pack so the friction plate side of things are sorted. Metal plate comments and Clutch centre to pressure plate clearance are the same as the older 12 tooth clutch above. Because of the 4 separate dished plates used in this pack; in racing it helps the bike get off the line more smoothly, the clearance may measure up to 1.8mm on its first use. As long as its dropped down a little within the next few hundred miles its fine.
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Ducati. 848 / Sport classic / Multistrada / ST3 / ST4 (all big wet clutch models)
Six ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch friction plates and springs.
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The clutches work fine at 1-1.2mm, 0.8mm is as low as you will ever need to go, the pulses from a big vee twin are pretty unsubtle so the delicacies of really small clutch centre to pressure plate clearances are not needed.
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Aprilia 450/550
Five ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch friction plates and springs.
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The clutches work fine at 1-1.5mm, 0.8mm is as low as you will ever need to go. The standard metal plates have a very square shape on their teeth. As set out in the instructions the standard plates have to be swapped for a set out of a Honda CRF450.
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Honda SP-1/2
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Six ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch friction plates and springs.
The clutches work fine at 1-1.5mm, 0.8mm is as low as you will ever need to go, the pulses from a big vee twin are pretty unsubtle so the delicacies of really small clutch centre to pressure plate are not needed.
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Honda CBR1000RR (2004/2005)
Six ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and springs.
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Uses standard clutch plates and springs. The clutches work fine around 1-1.5mm; 0.8mm is as low as you will ever need to go. Don't forget the cush rings need to be taken out from the back of the pack. For racing use we recommend these are put back in the centre of the pack (with their appropriate friction plate) as they soften some of the race start difficulties caused on all the CBR1000RR bikes by a weak basket.
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Honda CBR1000RR (2006/2007)
Six ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and springs.
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Uses standard clutch plates and springs. The clutches work fine around 1-1.5mm; 0.8mm is as low as you will ever need to go. Don't forget the cush rings need to be taken out from the back of the pack. For racing use we recommend these are put back in the centre of the pack (with their appropriate friction plate) as they soften some of the race start difficulties caused on all the CBR1000RR bikes by a weak basket.
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Honda CBR1000RR (2008 plus)
Six ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates.
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Uses standard clutch plates. The clutches work fine around 1-1.5mm; 0.8mm is as low as you will ever need to go.
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Honda CBR600RR 06 and on
Six ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and springs.
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Uses standard clutch plates and springs. The clutches work fine around 1-1.5mm; 0.8mm is as low as you will ever need to go. Don't forget the cush rings need to be taken out from the back of the pack. For racing use we recommend these are put back in the centre of the pack (with their appropriate friction plate) as they soften some of the race start difficulties caused on all the CBR1000RR bikes by a weak basket.
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Honda CBR929/954 2000 to 2004 (SC50)
Five ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and springs.
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The clutches work fine at 1-1.5mm; for full on racing 0.6mm is as low as you will ever need to go. Don't forget the cush rings need to be taken out from the back of the pack. This clutch uses standard 2.6mm thick metal plates; the pack can be thinned by using VFR800 (2.0mm) metal plates.
For full racing use a full size friction plate instead of the increased O/D one left after the cush rings are removed. Springs also may need to be changed, make sure they have the same I/D as the originals. Some kit springs are made with too small an I/D, using them can lock up the slipper mechanism.
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Honda CBR600RR up to and including 2006
Five ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and springs.
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The clutches work fine at 1-1.5mm; for full on racing 0.6mm is as low as you will ever need to go. Don't forget the cush rings need to be taken out from the back of the pack. This clutch uses standard 2.6mm thick metal plates; the pack can be thinned either by using the 'Sigma clutch shim pack' or by using Honda CBR900RR (2.3mm) 954 or 919cc models or VFR800 (2.0mm) metal plates.
For bigger power outputs (130 bhp plus) use a full size friction plate instead of the increased O/D one left after the cush rings are removed. Springs also may need to be changed, make sure they have the same I/D as the originals. Some kit springs are made with too small an I/D, using them can lock up the slipper mechanism.
If you are using Honda race kit parts, or are making more than 130bhp you should use the 'Pink' marked spring, part # 22401-MBG-000. This has the correct I/D and O/D. If the springs you have are not an easy fit do not use them. These racing springs are stronger than necessary with even full house Ten Kate engines only requiring 2 or 3 out of the five springs to be HRC type.
Clutch operation will be smoother with slightly less spring and/or a clearance around 0.8mm. If you need more spring for the clutch to hold under hard acceleration you should consider using one of our 33 degree ramp clutches to regain a smooth overall action.
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Honda CBR600RR 2007 on
Five ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and springs.
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This clutch has a reduced ramp angle of 33 degree’s designed to work with the stronger standard springs on the 2007 and on bike (the same as last years HRC racing spring actually).
The clutches work fine at 1-1.5mm; for full on racing 0.6mm is as low as you will ever need to go. This clutch uses standard 2.6mm thick metal plates; the pack can be thinned either by using the 'Sigma clutch shim pack' or by using Honda CBR900RR (2.3mm) 954 or 919cc models or VFR800 (2.0mm) metal plates. This clutch can be retrofitted to the older CBR600RR bikes.
For bigger power outputs (130 bhp plus) use a full size friction plate (preferably the same part number as the one next to the pressure plate in the standard pack) instead of the increased O/D one left after the cush rings are removed. Springs also may need to be changed, make sure they have the same I/D as the originals. Some kit springs are made with too small an I/D, using them can lock up the slipper mechanism.
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Honda CBR600RR 2007 Evo Corsa on
Five ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and springs.
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The clutches work fine at 1-1.5mm; for full on racing 0.6mm is as low as you will ever need to go. This clutch uses 2.0mm thick metal plates from a VFR800 or our 2.0mm titanium plates. The use of thinner metal plates significantly reduces the rotational inertia and weight of the clutch. This clutch can be retro fitted to the older CBR600RR bikes.
For bigger power outputs (130 bhp plus) use a full size friction plate (preferably the same part number as the one next to the pressure plate in the standard pack) instead of the increased O/D one left after the cush rings are removed. This clutch has a reduced ramp angle of 33 degree’s designed to work with the stronger standard springs on the 2007 and on bike (the same as last years HRC racing spring actually).
Springs also may need to be changed, make sure they have the same I/D as the originals. Some kit springs are made with too small an I/D, using them can lock up the slipper mechanism.
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KTM 990 LC8 (all models)
Six ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch friction plates and Suzuki GSXR1000K5-7 springs.
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The clutches work fine at 1-1.5mm, 0.8mm is as low as you will ever need to go, the pulses from a big vee twin are pretty unsubtle so the delicacies of really small clutch centre to pressure plate are not needed. Suzuki GSXR1000 K5-7+ steel plates will fit and are available in different thicknesses if you want to adjust the clearance or make up for pack wear.
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KTM RC8
Six ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch friction plates and Suzuki GSXR1000K5-7 springs.
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The clutches work fine at 1-1.5mm, 0.8mm is as low as you will ever need to go, the pulses from a big vee twin are pretty unsubtle so the delicacies of really small clutch centre to pressure plate are not needed. Suzuki Hayabusa steel plates will fit and are available in different thicknesses if you want to adjust the clearance or make up for pack wear.
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MV Agusta 1000
Four spring, eight ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch friction plates and springs.
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Suzuki Hayabusa
All years. Six ramps, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and springs.
Buy online
This clutch uses 6 x GSX-R 1000 K1-K4 clutch springs. It works fine between 1-1.5mm, you can go down to 0.7mm by replacing either on or both the 2.3mm metal plates in the pack with standard 2.0mm plates. The clutch can also be used on the SV1000 with the use of different metal plates.
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Suzuki GSXR 1000K1-K4
All years. Five ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and springs.
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This clutch works fine between 1-1.5mm, you can go down to 0.7mm. If you want to adjust the clutch different thickness metal plates are available either by using the 'Sigma Clutch shim pack' or by using standard Suzuki plates(available as standard Suzuki parts)
- Thickness Suzuki catalogue No.
- 2,3 21451-40F 00 Standard on GSXR 1000
- 2,0 21451-40F 10
- 2,6 21451-40F 20
We can supply these plates also.
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Suzuki GSXR 1000 K5 and on
All years. Five ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and springs.
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This clutch has lower ramp angles than the standard slipper clutch to work better and more smoothly with the standard, slightly stiffer springs of the later Suzuki’s. In addition to the changed ramp angles this clutch weighs in at about 400 grams (nearly one third!!) lighter than the standard item greatly improving throttle response, acceleration out of corners and gear-shift quality.
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Suzuki GSXR 600/750 K1-K5 inclusive
All years. Five ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and springs
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The clutch works fine around 1-1.5mm, 0.6mm is as low as you will ever need to go. Don't for get the cush rings need to be taken out from the back of the pack. This clutch uses standard mixture of 2.0 and 2.3mm thick metal plates; the pack can be thinned by using more standard 2.0mm metal plates or ones from the Honda VFR 800 (don't laugh, it's the same stamping!!).
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Suzuki GSXR 600/750 K6 and on
All years. Five ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and springs
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This clutch has significantly lower ramp angles to work better with the standard, slightly stiffer springs of the later Suzuki’s If you want to adjust the clutch different thickness metal plates are available either by using thinner standard Suzuki plates (available as standard Suzuki parts).
In addition to the changed ramp angles this clutch weighs in at about 500 grams (almost one third!!) lighter than the standard item greatly improving throttle response, acceleration out of corners and gear-shift quality.
The clutch works fine around 1-1.5mm, 0.6mm is as low as you will ever need to go. . This clutch uses standard mixture of 2.0 and 2.3mm thick metal plates; the pack can be thinned by using more standard 2.0mm metal plates or ones from the Honda VFR 800 (don't laugh, it's the same stamping!!).
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Yamaha R1 (Pre 04)
Five ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and spring
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This clutch wins UK National level car races on a standard clutch pack it works fine around 1-1.5mm.
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Yamaha R1 (2004/2005)
Six ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and spring.
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This clutch won the Canadian Superbike championship on a standard clutch pack. It works fine around 1-1.5mm but preferably near 1.0mm.
If the clearance is not correct, you will need to either change all the friction plates to new ones or replace some of the metal plates using different thickness steel plates as shims. Suitable alternative standard Yamaha steel plates are as follows; 5VY-16325-00 = 2.0mm thickness and 4BI-16325-00 = 2.3mm thickness. This clutch also fits the 2006 and on Fazer 1000.
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Yamaha R1 (06)
Six ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and spring.
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This clutch works fine around 1-1.5mm; preferably nearer 1.0mm.
If the clearance is not correct, you will need to either change all the friction plates to new ones or replace some of the metal plates using different thickness steel plates as shims. Suitable alternative standard Yamaha steel plates are as follows; 5VY-16325-00 = 2.0mm thickness and 4BI-16325-00 = 2.3mm thickness.
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Yamaha R1 (07 and on)
Six ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and spring.
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This clutch works fine around 1-1.5mm but preferably nearer 1.0mm. The clutch features different ramp angles to standard to work more smoothly in racing conditions and with harder springs. The lower ramp angles means it is better to leave the standard starter motor on when racing. In addition to the lower ramp angles the clutch is nearly 500grams (one third) lighter than the standard item improving throttle response, acceleration out of corners and the quality of the gear shifts.
If the clearance is not correct, you will need to either change all the friction plates to new ones or replace some of the metal plates using different thickness steel plates as shims. Suitable alternative standard Yamaha steel plates are as follows; 5VY-16325-00 = 2.0mm thickness and 4BI-16325-00 = 2.3mm thickness.
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Yamaha R6 up to and including 2005
All years. Six ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and springs.
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For track day use the standard plates are just fine; for full on racing starts though the standard plate seems real grabby. We firmly recommend you use Yamaha Factory race kit plates if you are going to be doing any full power launches.
The clutch works fine at 1-1.5mm, 0.8mm is as low as you will ever need to go. Don't forget the extra plate that needs to be taken out from the back of the pack. This clutch uses standard 2 .0mm thick metal plates; the pack can be thinned by using the thin plates from the old Yamaha XS750 or XS850 (don't laugh, it's the same stamping!!).
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Yamaha R6 (2006-on)
All years. Six ramp, wet type. Hard anodised in grey; Clutch centre only. Uses standard clutch plates and springs.
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For track day use the standard plates are just fine; for full on racing starts though the standard plate seems real grabby. The clutch features different ramp angles to standard to work more smoothly in racing conditions and with harder springs. We recommend you use Yamaha Factory race kit plates if you are going to be doing full power launches. In addition to the lower ramp angles the clutch is nearly 500grams (one third) lighter than the standard item improving throttle response, acceleration out of corners and the quality and speed of the gear shifts.
The clutch works fine at 1-1.5mm, 0.8mm is as low as you will ever need to go. This clutch uses standard metal plates; the pack can be thinned or thickened by using the different thickness plates included in the standard pack.
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Accessories
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Clutch pack shims; a set of different thickness metal plates to allow you to experiment with different thickness clutch packs. Just remove an existing metal plate, measure it all up and substitute one for the pack.
Preload spacers; different thickness preload spacers to allow adjustment of the main springs
Service kits; replacement centre springs, clips and ball bearings.
Copyright Neil Spalding 2002- 2014
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