The 2017 Sherco/Scorpa Clutch - A Big Change

Discussion in 'Trials' started by motobene, Sep 26, 2016.

  1. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,133
    Location:
    Wichita Mountains SW Oklahoma
    Here is a Sherco illustration of their new clutch. My earlier engineering hunches about what they would do to make this work were correct:

    upload_2016-9-26_11-19-39.png

    They can boast, but it's not 100% Sherco technology. Rather it's a flavor of the Xui R&D guy's GasGas clutch first introduced on the 2002 GasGas Pro, then later used in the Ossa and TRS (not sure about Vertigo). Same idea as the original with same 3-plate scheme, steel outer hub and primary, gear smaller diameter, and less thick. Same ability to handle more torque with a light lever pull while having fewer plates and being smaller. Hopefully in year 1, the same wonderful feel of a well set up GasGas clutch!

    What I'm not sure about is how they are rockering off (presumably) the outer hub to lift the Belleville washer-spring via the triangle plates. Notice also that the the outer part of the spring contacts what looks like a hard washer that sits on a thick sort of first plate.

    Sherco has done a very good job of fitting this type of clutch into the existing Sherco cases and adapting to pushing OUT on the triangle plates versus the GasGas method of pushing in from the clutch cover (this is why the Sherco triangle plates angle in rather than out).

    Unlike GasGas, however, the Sherco interpretation retains the removable clutch cover so you can get quicker access to the clutch and - this is fun! - watch it work dynamically.

    One of my earlier observations was that they would have to employ not the standard diameter clutch slave cylinder but rather, like GasGas, a smaller diameter slave cylinder. These types of clutches require MORE slave cylinder throw due to the leveraging of the triangle plates. And there it is in the illustration, a dinky slave cylinder diameter. Smaller bore, in I suspect the same casting, so it will look the same from the outside.

    This master cylinder definitely won't work on the direct-lift clutches! The previous master cylinder on a 2017 would result in a super stiff clutch.

    It is POSSIBLE they could sell a retrofit kit IF the primary transmission shaft is unchanged. The gotcha could be how they are retaining the assembly against the push-out force. I see there a bolt, not a nut, however. Here is the old set-up, nut on threaded shaft:





    So splitting the cases may be required to fit a new clutch.

    One rider recently said he rode a 2017. They are out? He said he still preferred the modified-to-4-springs clutch on his 300ST to the 2017. It will be interesting if they nail this thing first year. TRS had to learn as GasGas did to use a softer spring for most riders. If the first version of the Sherco clutch pull is on the stiff side, the majority will want less pull. Then there are the clutch plate materials and other nuances. But I'm confident that if Sherco don't nail it first time they'll get it right fairly quickly. But it's not so risky, as examples of this type of clutch abound.
    #1
  2. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,133
    Location:
    Wichita Mountains SW Oklahoma
    Very good report, Zuendapp! Just the kind of info that is great!

    The 2017 standard Sherco has the same ignition as my `16 Factory. So the motor, other than the clutch, is probably identical to the `16 Factory models, and they run really good! The suspension on the `17 standards is chrome plated steel Tech forks same as always, and probably that good working Olle shock. I could see how you were impressed. These newer Sherco/Scorpas impressed me so much I now own one.

    How was clutch pull on the new Sherco clutch compared to your GasGas?

    Were your clutch issues with the `14 GasGas from the master cylinder nipping the cup seals?
    #2
  3. Tomb Raider

    Tomb Raider Been here awhile

    Joined:
    Dec 15, 2010
    Oddometer:
    392
    Location:
    NW Washington
    Why is it, that all these manufacturers are taking so long to make a clutch that acts like it should. Dirt bikes and street bikes all slip, and lock in ? My 85 NH 700s and my 14 Super Tenere are hydraulic, my 2003 DRZ 400s is cable. All work like a clutch should. I just put a EBC Dirt Digger in the DRZ and love that thing now.
    #3
  4. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,133
    Location:
    Wichita Mountains SW Oklahoma
    Sorry, but I don't understand your reply. Which manufacturers? Trials bikes in general have had some of the best manual clutch action for a long time. They all 'slip and lock in' as they should.
    #4
  5. Tomb Raider

    Tomb Raider Been here awhile

    Joined:
    Dec 15, 2010
    Oddometer:
    392
    Location:
    NW Washington
    I thought that was the issue here ?
    #5
  6. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,133
    Location:
    Wichita Mountains SW Oklahoma
    I was not criticizing Sherco or any other manufacturer for long use of the multiple helical compression spring clutch that dominates almost all of motorcycling, including the three example motorcycles you cited. They work well. The new clutch at issue could work a fraction better, and that gets enginerds excited.
    #6
    Tomb Raider likes this.
  7. Tomb Raider

    Tomb Raider Been here awhile

    Joined:
    Dec 15, 2010
    Oddometer:
    392
    Location:
    NW Washington
    OK, Just one thing I've read on this site is how some Trials Clutches are not so good. That clutch you put up looks like Honda TRX-250 R clutch except for the slave part. U are a big part this site and info, keep R comin.

    But the top NEW doesn't.
    #7
  8. lineaway

    lineaway Long timer

    Joined:
    Oct 1, 2011
    Oddometer:
    8,429
    Location:
    nm
    It`s easy to be confused as all clutches have very easy lever pull any more. Bene takes that a step further with his wanting an ever lighter pull with more progression in even the most modern of bikes. I agree that a four spring clutch can at times work well. The confusion comes in at what expense you get his highly progressive clutch. When the top riders are using even higher spring rates for the aggressive riding they do. So an average person reading through the threads on clutches might come to the same conclusion as Tomb Raider. For what it is worth, if you ever have a chance to ride one of Bene`s bikes you will be impressed on how well everything works.
    #8
    motobene likes this.
  9. Norman Foley

    Norman Foley Devotee of the Husqvarna

    Joined:
    Mar 20, 2004
    Oddometer:
    1,999
    Location:
    New York... The Finger Lakes
    It's a 125, but my clutch works awesome, with super light pull on the my '17 GG. I am a trials novice, but I ride small bore enduro bikes and know how to use a clutch to modulate power and traction.
    #9
  10. laser17

    laser17 Long timer

    Joined:
    Mar 6, 2008
    Oddometer:
    1,439
    Location:
    Boston,Massachusetts
    Bene - To answer your question from above, Vertigo also uses a Belville washer style clutch. I think they use the full Xui design with the CF plates and stepped preload ring for adjusting the hit/lever pull as well.
    #10
  11. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,133
    Location:
    Wichita Mountains SW Oklahoma
    #11
  12. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,133
    Location:
    Wichita Mountains SW Oklahoma
    Interesting! With Sherco also adopting this type of clutch, the majority of trials bike manufacturers now have them. Beta and HRC Montesa may have eyeballs on this trend. Though the difference between the basic designs functionally isn't that great, the so-called 'diaphagm' clutch is slightly superior overall, including parts count and possibly manufacturing cost, though the unitized steel outer hub and primary gear is no doubt and expensive bit.

    That reminds me of my air-cooled VW days. Back in the `70s there were two clutch pressure plates available for the Veedubs, helical compression spring and diaphragm. The latter engaged more predictably and felt better under the left foot.
    #12
  13. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,133
    Location:
    Wichita Mountains SW Oklahoma
    Thanks!

    Hey I looked up the TRX 250-R clutch on Google Images and found it is just a conventional helical coil spring clutch with 5 instead of the more preferred 6 springs (`cause I can remove two if I want to with 6).

    Now you've mystified me regarding what 'top NEW' is!
    #13
  14. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,133
    Location:
    Wichita Mountains SW Oklahoma
    Good to know. Manufacturers tend to start out stiffer with these clutches then back off later. Last thing a manufacturer wants is a reputation for excess slipping under the more abusive riders. Then they build some confidence and back off on spring-related pressure to make the majority happier.

    One thing hard to change after the release is slave cylinder diameter. If the clutch feels stiff because the diameter is a fuzz too small it's a DOH! moment.

    I see on closer inspection the casting is in fact more anorexic on the exterior shape.

    Sounds like you just got unlucky with your particular GasGas by having multiple non-optimal elements in a functional group on the same bike.

    Where have those non-optimal BrakTec master cylinders gone? In dusty boxes? I know how to make them work well and would gladly do some good with them :-)
    #14
  15. TrialsFish

    TrialsFish Adventurer

    Joined:
    Sep 23, 2016
    Oddometer:
    12
    The other bonus to switching to a belville design is that it eliminates the clutch "Creep" at high rpms. Both my 15 Beta 4t and my 16 Scorpa 300 have a noticeable creep when winding the motor up at a stand still. I haven't had a chance to test a 17 sherco yet but I have been told by a few of the team riders that it eliminates it completely.
    #15
  16. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,133
    Location:
    Wichita Mountains SW Oklahoma
    I am mystified again, this time about creep at a standstill, as I've not experienced that.

    Are you talking about being pushed forward when balanced and stopped in gear, clutch lever pulled in, then holding the motor wide open? Perhaps to 'clean out' the motor?

    Maybe I don't experience creep because I NEVER need to 'clean out' a well jetted motor after warm-up.
    #16
  17. TrialsFish

    TrialsFish Adventurer

    Joined:
    Sep 23, 2016
    Oddometer:
    12
    Yes that is the creep I am talking about but I mean in the context of winding up the motor wide open for a splatter from a dead stop. I also agree with I never need to clean out my properly jetted scorpa.
    #17
  18. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,133
    Location:
    Wichita Mountains SW Oklahoma
    OK, thanks. I'll check into this.

    The clean-out issue is from a fooling of the brain. Fuel utilization is a function of load. Revving out an unloaded 2 stroke it can have the motor 4-stroke more some and thus sound 'dirty' and in need of a 'cleanout.' Beyond the need during warm-up to blow out oil that has settled into the bottom of the crank area after the bike sits a few days, there is zero need to do in-event cleanouts on properly jetted bikes.
    #18
  19. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,133
    Location:
    Wichita Mountains SW Oklahoma
    The helical coil spring clutches are larger in diameter and have many more plates. The added surface area running in oil can create some 'torque converter' effect, especially when using thicker oils and on clutches that tend to have a little more drag.

    When I pulled the 2 clutch springs, I observed the pressure plate was lifting off on a slight tilt, so I shuffled the remaining 4 springs around until the pressure plate lifted off level. Perhaps that will reduce a torque converter effect?

    I have been using the Silkolene Light in the Sherco. My clutch still hits a little fast so I got a quart of the slightly thicker Silkolene Comp Gear. This is stated as semi-synthetic so it will have a higher viscosity index, making it stay thicker when hot. That should also increase the torque converter effect. Will report on that after I try it.
    #19
  20. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,133
    Location:
    Wichita Mountains SW Oklahoma
    Here is the 2017 clutch assembly:



    Here is the 2016 Factory clutch assembly:



    As you can see, the new clutch drops parts count by a lot. Also, the older clutch outer hub is two parts riveted together with more parts. The 2017 hub is single piece steel just like the GasGas part.

    Here is the 2017 transmission assembly:



    The 2016 Factory assembly below shows the external thread is there on the end of the clutch transmission shaft. Note the parts are not numbered in this particular illustration, but you can see in the parts number difference of the clutch transmission shaft in the list.

    The 2017 shaft does indeed have an internal versus external thread, as I suspeted:



    I have also confirmed the center cases part numbers are different, the 2016 is 5547, and the 2017 is 6387.

    The slave cylinder is now 6590 versus the previous 5528.

    And very notably, the countershaft sprocket for 2017 is a 9 tooth versus the 10 tooth in 2016, and the rear sprocket is now 44 versus 42!

    Retrofitting 2016 and previous with the new clutch is not a practical option as too many parts are different.
    #20
    laser17 likes this.