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Discussion Starter #1
Hi everyone, I'm posting this up in the hope that what I have worked out a fix for the bloody annoying issue of clutch drag on the EXC models. I haven't actually done the mod to my bike yet so I could be setting myself up for a fall!

Basically I was getting so pissed off with this issue that I thought that I'd sort it out once and for all, I have tried ATF (650cc) and I think that helped but it did not get rid of the issue. I have taken my clutch apart and checked all of the plates for warps, they are all OK and they are all over the minimum thickness, I have set up the XYZ ring as per the manual and I have checked the clutch basket for notches and it is OK. (Only minor notches that you always get).

After doing some measuring I found that the slave cylinder can move a total of 5.2mm, when the clutch is assembled the slave is pushed back up its bore around 3.2mm leaving 2mm before the piston bottoms out in its bore. This means that the piston in theory could move the pressure plate 3.2mm before it reaches the end of its travel and locks up.

I have modified my clutch lever to give the master cylinder piston a bit more stroke, this did move the lever further from the handlebars, anyway when the lever is pulled the clutch pressure plate on my bike moves out 1.79mm, my theory is that if I can increase this movement then the clutch plates will move further apart which means that it hopefully won't act like a fluid coupling like it does at the moment!

The mod I am going to try is to use a different master cylinder, have just purchased a second hand a Brembo master cylinder off ebay which came of a Ducati, the piston is 13mm which is 30% bigger than the 10mm KTM one, all things being equal (like the stroke of the piston) then this should move the pressure plate another 30% which takes it out to 2.3mm. In theory the clutch lever should be 30% harder to pull and this would be the case if the clutch used 'normal' coil springs but diaphragm springs are very odd things, the pressure required to move them can actually decrease at certain points in their movement so God knows what the pressure at the lever will be.

Plenty could go wrong with this mod or it might just not make any difference!

If this all works I'll post up my results. If I don't post anything up it ain't worked!
 

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A 13mm master is 69% bigger than a 10mm
 

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Discussion Starter #3
A 13mm master is 69% bigger than a 10mm

Eh, how did you work that out? Just pulled this off the web...

To calculate the percentage increase: First: work out the difference (increase) between the two numbers you are comparing. Then: divide the increase by the original number and multiply the answer by 100. If your answer is a negative number then this is a percentage decrease

In my case the difference between the numbers is 3, so according to the above the percentage is 3/10 X 100 which works out to be 30% I hope I've got this right!



EDIT... Oh fuck, the area is 69% bigger, that's fucked up everything!:eek::eek::eek::eek:

FUCK FUCK FUCK! 11mm piston is 21% bigger, 12mm piston is 44% bigger....dunno which one to go for now.
 

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Discussion Starter #4
Just purchased a 12mm unit, I now have a 13 and a 12mm unit, oh well that will teach me to jump straight in without thinking! (Anyone on here ride a Ducati and need a clutch master cylinder? LOL )
 

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Easy mistake to make, and I doubt you'd be the first or last to make it.

What highlighted it to me years ago was the difference between the same brake setup with a 12mm and a 1/2" master cylinder. Totally different in terms of feel.

Was suffering a similar fate with clutch drag earlier in the year. Switching from Putoline back to Silkolene light gear oil cured it for me.
 

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Its not just on the EXC though, I took my month old 300 back yesterday for the dealer to have a look at. They found a load of air in the clutch hose and after a bleed through the clutch felt a little betterbut still had a fair bit of drag. The mechanic said that every off road KTM has the same problem to demonstrate it he got a brand new 4T 350 crosser, plonked it in gear and told me to push it, the rear wheel was virtually locked solid.
 

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The mechanic said that every off road KTM has the same problem to demonstrate it he got a brand new 4T 350 crosser, plonked it in gear and told me to push it, the rear wheel was virtually locked solid.
If he did that with the engine off he probably screwed you...
 

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my 300 starts to drag a wee bit only once the oil has over 10 hours on it ..... that is with 700ml rather than the stated 900ml (700ml is enough for the oil to show on the level screw) - using castrol/elf/motul/ipone 10w 50. + 5.1 clutch fluid.
 

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You could just run Putoline Nano Trans GP and forget measuring or needing to take apart anything. No drag. No wear and perfect action for 20 hours. You tend to notice it’s ready for a change as you become aware of having to change gear, up to that point it’s so slick it’s changed gear without a thought. Perfect.
 

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Discussion Starter #11
You could just run Putoline Nano Trans GP and forget measuring or needing to take apart anything. No drag. No wear and perfect action for 20 hours. You tend to notice it’s ready for a change as you become aware of having to change gear, up to that point it’s so slick it’s changed gear without a thought. Perfect.
OK so did you have clutch drag at any point then you filled the box with Nano and it totally fixed the issue? If you did then that is something worth trying for sure!
 

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Discussion Starter #12
OK so the Putoline oil may well be the fix for this issue but it ain't cheap and I've started down this route of fiddling about with the clutch so I may as well keep trying in order to see if it is possible to sort it out without using the Putoline oil. I've just put 650cc of ATF in the gear box and with the clutch pulled in I rotated the rear wheel whilst the engine was in gear in order to get the oil around the clutch plates. Then with the clutch lever tied up so it was pulled back to the handlebars and the bike in first gear I used a digital weight gauge to rotate the back wheel by pulling on the bolt that forms part of the rim lock. It took 1.6kg of force to turn the wheel.

Things are not looking all that good though because I then drained the oil, removed the clutch cover plate and removed the clutch pressure plate, it still took 1.6kg of force to turn the wheel even with no pressure on the clutch pack! This must just be due to the plates sticking together, this does not bode well! (Although I guess with the engine running the plates might shake apart I suppose)

I have another idea! I have worked on some engines where the plain plates have a section cut out of the circumference so that they are out of balance, the plates are then stagger in the basket so that the whole clutch is balanced. The idea is that the out of balance plates tend to pull themselves away from the friction plates. Only problem with this is that there is no going back if I cut lumps off the plain plates! (Apart from buying new plates).

Anyway its keeping me busy in the garage if nothing else!
 

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Discussion Starter #14
Interesting! I'll check that out on my clutch. I can see that causing some issues if the xyz ring is a mega tight fit on the spring although as long as the pressure plate does actually move away from the clutch pack the clutch should disengage, if the xyz plate and spring somehow stops the pressure plate from moving away from the clutch pack you should feel that by the clutch lever on the handlebars locking up of being jerky.

I might just open up the centre hole in the spring a touch anyway!

EDIT...Reading your post again I see that your pressure plate was not lifting off the clutch pack 'square', that would 'defo' cause some issues!
 

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Have you gone through all the standard things first? Use the OE spec'd motorex oil, fresh clutch pack, basket and hub not notched?
 

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Discussion Starter #16
Have you gone through all the standard things first? Use the OE spec'd motorex oil, fresh clutch pack, basket and hub not notched?
I did use the 'standard' oil when I first got the bike, the clutch was not all that good. The plates are not new but I have carefully checked them all, none of them are warped, I checked them on a glass plate and they are all above the minimum thickness. I stacked all the plates together then tried to compress them by hand, they were solid.

The basket as very minor marks on it, I can not really call them notches. The hub is not notched and in this respect the design is quite good because the plain plates ride on hard steel tubes rather than the hub itself.
 
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Nano saved my rev3 clutch issues. I was about to start filing plates and basket and doing all kinds of mods that I’d been told about and read about. Someone suggested using nano not atf. I thought why not. It’s easy and not expensive due to the oils longevity. I changed it to nano and it was better. I then changed it again for the other 500ml and no more clutch issues for the rest of the time I had the bike. When I got my 200 as a new bike I put it in that too. The clutch has never dragged and still no wear on the plates at 220 hours. Nano will be going in my 150 from day one based on this experience.

Atf works but it’s not for me.
 
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You could just run Putoline Nano Trans GP and forget measuring or needing to take apart anything. No drag. No wear and perfect action for 20 hours. You tend to notice it’s ready for a change as you become aware of having to change gear, up to that point it’s so slick it’s changed gear without a thought. Perfect.
But two things would be worth to be done:
.) fill less than specified
.) make sure the clutch is properly bled
 
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Discussion Starter #19
Hmm, this Nano stuff does sound good, maybe I should have tried it before spending money on master cylinders! :confused::confused::confused:
 
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Discussion Starter #20
Tried both a 12 and a 13mm master cylinder today, what a waste of time (and money!) neither of them lifted the pressure plate more than the standard master cylinder. I guess the stroke of the new units was less than the standard unit so even though the diameters were bigger the total amount of fluid being displaced was the same as the standard setup.

Anywho, I've ordered some Nano GP so I'll see how that goes, I'm sort of thinking that I should just replace the clutch plates even though mine seem fine, actually there is a touch of blue on a couple of the steel plates.


What plates have you guys used or is the KTM stuff the only stuff worth using?
 
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