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Discussion Starter #1
I need to lighten the clutch pull for my wife (she suffers with Carpal tunnelI) have searched the forums and found a bit of info, namely extending the lever at the gearbox 18mm and that the 2015 model had a lighter pull due to some slight tweaks. Does anyone know what these tweets were, can they be done to a 2014. Or is there aftermarket options?
 

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Extending the actuating arm at the gearbox will lighten clutch action at the expense of a longer lever travel.
 

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Discussion Starter #3
Longer clutch pull isn’t going to work to be honest, she has very small hands so the adjustable levers we have fitted may not let us get away with the longer travel.
 

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Have you considered getting a Rekluse automatic clutch? It should let her ride without ever touching the clutch lever (including stop and go)

https://www.ktm.com/powerparts/engine/engine-parts-4-stroke/rekluse-radius-x-centrifugal-force-clutch-kit/?year=2015&category=KE3-16007255/KE4-16007257&segment=Naked Bike&model=F4303O1

It's only listed for 2015+, ditto on Rekluse's site. I'm not aware if there are any differences between 2014 and 2015 models that would make it not fit...
According to some retailers, it should fit all Dukes (ex https://www.ebay.com/itm/NEW-KTM-390-DUKE-RC-Rekluse-Radius-X-Centrifugal-Force-Clutch-Kit-2013-2018-/133047434305 )
 

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Discussion Starter #5
I hadn’t even thought that could exist! I will look into it as an option thanks.
 

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If my high school physics doesn't fail me, as long as you have the same amount of work to do (pulling the clutch apart against the springs), you can only trade off force vs distance. No matter which method you chose, wire or hydraulics, the only way to decrease the force of the pull is to increase the distance you need to pull, which is a problem if she has small hands.

Granted, high school physics doesn't take friction into consideration - if there's considerable friction within the clutch cable which causes the stress, rather than the force of the clutch springs, you may gain on moving to a hydraulic clutch. But if that were the case, your first step would be to lubricate (or replace) the cable. A properly maintained clutch cable has very little friction and the force you feel on the lever is purely from the springs.
 

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A good point. I don’t regard the 390 as having especially strong clutch pull. A lot of people use only one or two fingers.
 

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As I mentioned, depending on the MC you choose as in a larger diameter MC will replace the same hydraulic fluid to the operating cylinder easier than a smaller diameter MC.
I think this will make the clutch movement at the handlebars less "long" and lighter to operate, no?
 

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There's no free lunch :) The energy to expand the clutch springs has to come from somewhere. In physics, Work is literally Force x Displacement, if you decrease one, you need to increase the other. With a hydraulic system, you're just replacing mechanical leverage with hydraulic leverage. The ratio of cylinder diameters is a direct analogue to the ratios of levers in a mechanical system, and the end effect is the same.

So if there's no benefit to using hydraulic systems, why do some bikes use them? Or why did we go from cable-operated brakes to hydraulic brakes? The short answer is a hydraulic system is more consistent and delivers better feel because the sides of the hydraulic line expand less than a cable. This is especially needed for brakes, where you tend to extend prolonged, large force and you want to be able to modulate it minutely. The smaller flex of the system means your actions are more directly transferred to the slave, and you're not wasting a lot of that force on stretching a cable, more of it goes directly to the brake pads / clutch springs.

But in general, even 600 supersport bikes, like the newest ZX6R, often come with cable-actuated clutches, because it's just not that important to have these almost-on-off devices controlled with the precision and efficiency of a hydraulic system.
 

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Discussion Starter #11
As I mentioned, depending on the MC you choose as in a larger diameter MC will replace the same hydraulic fluid to the operating cylinder easier than a smaller diameter MC.
I think this will make the clutch movement at the handlebars less "long" and lighter to operate, no?
A larger diameter piston in master cylinder will reduce lever travel but increase load (volume of fluid being moved). A smaller diameter will lighten the load but increase the travel required to fully disengage the clutch.

Big Mac has hit the nail on the head with his post. I converted my Buell to a hydraulic clutch, effort is exactly the same - I did it because the original was prone to allowing water into the gearbox.

I see there was modifications on the 2015 bikes that made it lighter, I don't suppose anyone knows what these were?
 

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The 2017 Duke does have a very light clutch,
But it appears to have a very zig zag cable run (Compared with the single curve aimed for by classic bike fettlers) so there may be a lot of friction which a hydraulic system would avoid?
 

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This is a 2016 Duke though.

The 2017 Duke does have a very light clutch,
But it appears to have a very zig zag cable run (Compared with the single curve aimed for by classic bike fettlers) so there may be a lot of friction which a hydraulic system would avoid?
 

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clutch cables

Hi
Same principle applies though.
If the clutch cable curve is simple and smooth there wont be much friction so a hydraulic clutch wont help much.
If the cable curves sharply or back and forth there will be more friction and probably lost movement so a hydraulic clutch will help.

You can get some guide by seeing if the cable moves when the clutch is pulled. If it wriggles under your had as the lever is pulled that indicates lost movement and friction in the cable
 

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You can also unhook the cable from the engine and see if you get noticeable friction by pulling an unladen lever. I'd be surprised if a well-lubed cable was grabby due to being weirdly routed, that'd be horrible engineering on KTM's part.
 

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Discussion Starter #16
Judging by what people have said, the new model does have a lighter clutch, this is either due to lighter clutch springs or a slightly different design somewhere - like longer actuating lever at the gearbox end of the Bowden cable (for example)

Is there no-one who has had both bikes apart and spotted anything?
 

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I believe the change was made earlier, there was a mid-life upgrade of the first gen Dukes that included a slipper clutch. I can't find reliable info on whether the second gen Dukes got a different clutch than the upgraded first-gen, but it's definitely also a slipper.

Slipper-assist clutches tend to have an easier pull than normal clutches, it's not a question of cabling but rather of using weaker springs, allowed by the more efficient shape of the contact surface.

Apparently pre-upgrade first gen Dukes may be retrofitted with the slipper clutch, at lest according to this thread: https://www.ktmduke390forum.com/forum/engine-technical-discussion/24898-oem-slipper-clutch-upgrade.html

Might be worth checking which clutch is in Deb's Duke and how much the OEM slipper clutch found in the newer model costs. The parts numbers on https://www.bike-parts-ktm.com/ may tell you if the clutch is different and/or interchangeable


From what I see, the 2014 model has 5 springs on the clutch:
https://www.bike-parts-ktm.com/ktm-motorcycle/390_KTM/2014/DUKE/390-DUKE-WHITE-ABS/CLUTCH/720/26/0/720
The 2016 model has 3 springs, which signifies a lighter-pull slipper clutch
https://www.bike-parts-ktm.com/ktm-motorcycle/390_KTM/2016/DUKE/390-DUKE-WHITE-ABS/CLUTCH/670/25/0/670

The 2017 second-gen model's clutch assembly looks the same as 2016. In fact, the part number is the same since 2015+:
https://www.bike-parts-ktm.com/ktm-motorcycle/assignment_spare_parts/90232111010
 

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From what I can tell by the parts catalogue, 2015+ models have a different CLUTCH RELEASE LEVER CPL. and BRACKET CLUTCH CABLE, but otherwise are housed under the same cover. The gearbox main shaft is also the same.
 

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Discussion Starter #19
Big_Mac, as ever, you’re a star. On fitting the BoosterPlug is noticed that the outer clutch cable has worn and the wire is all rusted, just ordered a new cable as it was only £15 delivered! I will see what that’s like. Thanks for the info & the links I will look into it. ?
 

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Discussion Starter #20
New cable fitted. As worn as the old outer cable was, I think the thin tube that houses the inner cable was still in good shape as the new cable doesn’t seem and better. Sitting on the bike, Deb seems to think that it’s actually going to be ok. Time will tell.....
 
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