Sigma slipper clutch - first impressions

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misterdimwiddy
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Sigma slipper clutch - first impressions

Post by misterdimwiddy » Mon Sep 30, 2013 10:07 pm

First time out today with Sigma unit fitted. Have used original (high mileage) standard plates and springs.

Image

Brands Indy Club MSV day with blue sky from dawn to dusk. Lovely. Bike did not miss a beat; just drank 500ml of Castrol Power 1.

Immediately obvious even on sighting laps that usually large amount of engine braking is much reduced. No drama though as 320mm discs are more than up to the job. Niel Spalding reckons you loose about 80% of the original engine braking which worried me before I rode it but it feels very good.

Clutch lever makes a curious 'cable has just snapped' type feeling when the clutch does slip but once it's done it once or twice it is no bother and then goes pretty much un-noticed.

Over all impression for what is a pricey mod is that it is very beneficial on the track. Flat out in fourth approaching Paddock and you can simply knock it down into third at very high revs, brake and turn in. No fear of the rear locking/fish tailing, beautifully stable and minimal over revving on the over-run. It used to rev very high with the stock clutch when changing down.

Same story entering Druids, bottom bend and Clearways. I never once felt as though I was rushing into a turn too fast (which I do when I am trying too hard) and with the prospect of rear instability gone, you can simply concentrate on going in faster and getting your line through the turn. Enabled me to really get the jump on many of the IL4's out of the corners.

I recommend the upgrade and believe that the claims Sigma make for the unit are all valid, particularly with a big high compression twin.

Just a shame that it is not a visible mod and the only evidence I have for my big spend is a Sigma Performance key fob and a small cardboard box in my shed!

TRX now tucked away for the planned winter mods.

The more I do to the bike the more I love it!

coxylaad
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Re: Sigma slipper clutch - first impressions

Post by coxylaad » Mon Sep 30, 2013 11:05 pm

looks good. how much did you pay for it if you don't mind me asking?

cobbadiggabuddyblooo
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Re: Sigma slipper clutch - first impressions

Post by cobbadiggabuddyblooo » Tue Oct 01, 2013 1:42 am

I shall be fitting mine in about two months. Any mods needed to get it to fit inplace to the std set up???
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misterdimwiddy
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Re: Sigma slipper clutch - first impressions

Post by misterdimwiddy » Tue Oct 01, 2013 1:00 pm

coxylaad wrote:looks good. how much did you pay for it if you don't mind me asking?
£660 so obviously not a cheap mod.

I've put so much into the bike already that it was a shame not to go the whole hog.

New FCR's, 878JE, crank regrind, YZF front and rear, Akra etc etc

The turbo went on my mates Golf recently and that cost him £650 so for me it is not that difficult to spend hard earned money on a luxury item instead of a bill you were not expecting.

Would not bother fitting one for the road though.

misterdimwiddy
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Re: Sigma slipper clutch - first impressions

Post by misterdimwiddy » Tue Oct 01, 2013 1:11 pm

cobbadiggabuddyblooo wrote:I shall be fitting mine in about two months. Any mods needed to get it to fit inplace to the std set up???
Nothing really. Clutch nut torque is much tighter (120Nm?) than Yamaha spec (70Nm) but checked with Sigma and he tells me that they are all done that tight. All of the basket spacers are as for original Yamaha.

Also the lever actuation insert that pokes through the centre of the pressure plate seems very sloppy (because you have to take out the face roller bearing used in the original). The new clutch has a roller bearing instead and from an engineering point of view it looks all wrong to me! Sigma again reassured that all would be OK and it is.

Measuring up to ensure the stack height is correct is easy with a vernier caliper; mine was 1.40mm which is correct for a big twin. Changing this (1.00 to 1.4mm recommended) with thinner 1.2mm plates (XS750) alters the point at which the clutch slips.

I am sure you will have no problems but let me know if I can help if you do.

The feeling at the lever is unusual the first few times it works but soon becomes normal.

I ride using the clutch exactly as I did before the slipper (using the lever); no banging down three gears and expecting it to cope with such abuse (which lots of R6 riders do apparently).

I feel it will help transform my track day riding.

cobbadiggabuddyblooo
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Re: Sigma slipper clutch - first impressions

Post by cobbadiggabuddyblooo » Tue Oct 01, 2013 11:21 pm

Excellent thanks for that. I know Neil mentioned about the pushrod and wasn't sure on things there as they had never actually fitted one themselves to a TRX about 12 mths ago when I purchased mine. So I'll make a point of measuring the two bearings though as a reference .
laughter is the best medicine

misterdimwiddy
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Re: Sigma slipper clutch - first impressions

Post by misterdimwiddy » Wed Oct 02, 2013 7:05 am

In the image above you can see the Sigma radial ball race with the actuation spigot poking out towards you. This is where the sloppy fit is. There is about 2mm difference in the ID of the bearing and the OD of the shaft.

In the stock clutch there is a radial face type ball race which has to be removed.

The actuator spigot locates in the cover casting and so it is not as loose as it first seems when the motor is back together.

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