790 Reported Clutch failures - My 12k mile examination

Discussion in 'Parallel World (790/890)' started by windblown101, Nov 10, 2019.

  1. mrmoto

    mrmoto Just another inmate

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    +1 on the oil jet considerations. Correct on the less "less oil = more heat = glazed discs/plates = slipping clutch + overheated springs (= under spec measurement)

    Back in my 950 SE days, I experimented with oil jet sizing and ended up removing (don't do this without researching!) the oil jet. I also drilled MANY more holes in the inner basket to allow more uniform oil flow through the discs, and +30% stiffer springs. Clutch action was SO much better!

    In a related topic... I assume a high quality 100% synthetic oil? PowerSyn 10w-50 was my go-to... The oil selection will affect clutch overheating and therefor wear/issues. [Ducking my head] How often do you change the oil?
    #21
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  2. windblown101

    windblown101 Long timer Supporter

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    In my case 1st oil change was at 600 miles; 2nd oil change at just under 3000, third one at about 8k miles (5k on the oil, I was traveling at the time). Motorex on the first 2 changes. Amsoil on the third. However my clutch issues are no where near what some others have experianced. I was not experiencing any unusual clutch behavior. Simply wanted to have a look.

    New springs and clutch pack are in route and I'll have them early next week. I'm installing new rather than going with the original ones out of an abundance of caution. The ones in there would likely be fine. I dont see signs of glazing on the discs or plates and as mentioned they are in spec. But the clutch obviously had gotten pretty hot at least once in its life evidenced by the cooked (but not carbonized) oil on the centerplate.

    I'm not ruling out oil flow as a potential issue, or the possibility that clutch adjustment may have played a part, or that the clutch may simply be more prone to heating due to its design. Given that some of the early clutch problems have cropped up on mostly street ridden machines I'm less inclined to think the combo of TC and clutch work is a primary cause in all cases. A production variance with some componant being out of spec on some bikes cant be ruled out either, but certainly not a proven fact at this point.

    I don't have an oil pressure adapter plate to check the affect of a larger oil jet so I'm not inclined to experiment with oil jet size. Instead I think I'm going to switch to Motul 7100 10-40, make a point of having a slight bit extra play in the clutch lever and will check the clutch in 3k miles to see how it looks.

    I might even put an extra washer on the clutch springs to reduce the slipper affect slightly. By the time I check the clutch again hopefully folks with much more experiance in clutch design than I will have determined if there is a design issue to be rectified or not.
    #22
  3. justinope

    justinope Long timer

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    Yeah it seems like drilling out the oil jet to .5 mm instead of .3 mm is a solution some owners are pursuing from some replies I've seen on the 790 facebook groups.

    RE your question: my bike has been dealer maintained according to the maintenance schedule prescribed in the owner's manual, nothing any sooner than those intervals since its been ridden rather gently I hate to admit.

    I saw Bill Cairns is trying to organize a law suit against KTM UK on facebook in the big KTM 790 group. Was pretty sad to read so many owners are commenting on his post to "suck it up" or "sounds like you need a Honda" just because they didn't get hit by the issue like others did.. being straight KTM apologists for no good reason, was sad to see that
    #23
  4. windblown101

    windblown101 Long timer Supporter

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    Agreed. It's a shame it may come to that but if I had a clutch explode early on and was denied warranty and then found out others were experiencing the same thing happen to them I'd be wanting answers.

    Those answers, whatever they may be are not likely to surface without a lawsuit. As a manufacturer I imagine it's a tricky business deciding whether to warranty a wear item or not when the cause of the failure may not be known with certainty. Replace one and the flood gates open, justified or not. Ignore a potential issue and you might get your hat handed to you.
    #24
  5. kubcat

    kubcat Been here awhile Supporter

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    https://advrider.com/f/threads/team...our-bank-account.1413859/page-3#post-38795296

    Here's a post that indicates KTM is aware of the problem with a lack of oil in the clutch and addressed it in the 890 engine design. Of course there have been some observations that the poster is less than objective, so there may be some speculation or unfounded assumptions being made. Gave me pause, and I assume the minimum we 790 owners would want to consider is rejetting/drilling before too long.

    Maybe have to consider a trade up to the 890ADVR when it comes out in 2021.
    #25
  6. windblown101

    windblown101 Long timer Supporter

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    Saw that too. Not saying it's not true but I'll wait for a less "enthusiastic" source before I lend much credence to it. The same source loudly claimed the 790 fuel pump/filter design was would cause owners endless heartache, and he had a solution to offer... LOL.

    A bigger jet and perhaps a hole drilled into the clutch push rod if needed would seem to be the trick if lack of oil flow is the problem. I'll hold off on that one for now. The problem with solutions to this type of problem which takes time to develop is a lot of miles have to be ridden to really know the outcome. I'd much rather have to replace a clutch pack once a year (if actually needed) than drop oil pressure too low to the rest of the motor.
    #26
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  7. Velociraptor

    Velociraptor TrackBum Super Supporter

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    Installed the Rekluse Torque clutch today. Very easy job. 1,800 miles on my 790r with 70% street 30% dirt including some tough rocky riding. OEM clutch looked OK in my opinion. Clutch pack measured 36.5 which is basically no wear. The three springs were 42.9, 43.03, and 43.09 which is also close to new. There was a small amount of oil pooled at the end of the clutch shaft which makes me think all is working well on my bike. IMG_1568.jpeg IMG_1567.jpeg IMG_1563.jpeg IMG_1566.jpeg IMG_1565.jpeg IMG_1562.jpeg
    #27
  8. windblown101

    windblown101 Long timer Supporter

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    As a follow up - New clutch pack and springs arrived today. Old springs measured a bit over 1mm shy of the 43mm minimum length called for in the repair manual. The new ones measure 43.95mm.

    Now I'm off to install the clutch and check valve clearances while I'm in there to replace a leaky valve cover gasket. If all goes well and I'll have it buttoned up and ready to ride tomorrow. :clap
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  9. AdvRonski

    AdvRonski They call me......Ronski

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    I decided to take a look at my clutch, with 8000 miles on the bike. I haven't had any clutch issues, but the bike gets ridden hard, so I was curious about the condition of the plates.
    The pressure plate looks good from the outside-
    IMG_20191121_105323.jpg

    The clutch springs are within specs, but with 15mm of installed preload, I don't think 1 or 2 mm's would make much of an impact on it's operation.
    IMG_20191121_105531.jpg

    The clutch pack is in excellent condition, so that's great. But, I was curious how the slipper/booster mechanism operates. The outermost steel clutch plate is larger in diameter than the rest, and indexes to the pressure plate. Then, slight clutch slip on decel will rotate the pressure plate relative to the hub, and the ramps will engage and take up some of the pressure from the clutch springs.
    IMG_20191121_110225.jpg
    IMG_20191121_110400.jpg

    Any clutch slip under power, will rotate the pressure plate in the opposite direction, relative to the hub, engage the other set of ramps, which create additional pressure to prevent clutch slippage. I see plenty of oil in the interior of the clutch hub, and my personal opinion is that clutch failures are not related to insufficient oiling of the clutch. I still feel it's a case of an inadequate amount of freeplay at the clutch lever, which allows slippage to begin, and then prevents the ramps from adding any additional clamping force. Once the plates start to overheat, no amount of engine oil would provide enough cooling to prevent catastrophic damage to the clutch, if the rider keeps feeding power through the slipping clutch.
    Just one guy's opinion, but as a Automotive Master Tech for over 40 years, I saw plenty of destroyed clutches, with the majority of them being operator-induced.
    #29
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  10. windblown101

    windblown101 Long timer Supporter

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    Nice, that clutch looks mint. Thanks for weighing in!

    I plan to monitor free play closely moving forward with my new springs and clutch pack and will take another peek inside again down the road. As you mentioned even a slight bit too tight on the freeplay could prevent the ramps being able to rotate fully and achieve full clamping force. That's why I didn't even bother talking to the dealer about mine. I suspected it was user error. For less than $200 bucks I'll call that a cheap lesson.

    When I pulled mine apart the bike had not been run for a few weeks and the clutch was much drier, but had also had a lot of time to drain. My oil jet wasn't plugged.
    #30
  11. Toddv

    Toddv Been here awhile

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    I would tend to mostly agree, and it seems like most of the folks that had clutches burn up and explode didn't even realize they were slipping so it's probably safe to assume they weren't monitoring freeplay in the lever. For us guys who wrench on our own stuff and are in tune with our machines it would be picked up right away if the clutch was slipping but not for everyone. I picked up my 2020 R today and I checked freeplay before I left the parking lot, it was good at the lever and also at the arm at the clutch cover.

    but, if the oil jet did clog up, it would wear the clutch prematurely and could cause the issue. Once the plates are worn to the point they are slipping heat takes over and causes the catastrophic failure if the rider doesn't catch it. All the clutches I've seen pictures of that failed were worm completely through the friction surface and the steels were black and blue from heat, the aluminum (at least they look like they are aluminum?) friction plates aren't going to tolerate that kind of heat.

    So yea, Both scenarios are possible IMO but I think improper free play is probably the most likely culprit.
    #31
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  12. TheGr8Pumpkin

    TheGr8Pumpkin Been here awhile

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    I was going to say the exact same thing. Quite a few of the people I have heard complaining about destroyed clutches are also self-admittedly non-wrenchers . . .
    #32
  13. TrailTrauma

    TrailTrauma Nemophilist

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    I wonder if any of the clutch failure population installed the Camel 1 finger clutch 'without' paying attention to the need to tweak the clutch lever free play afterwards.
    #33
  14. Velociraptor

    Velociraptor TrackBum Super Supporter

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    I have the Camel product but paid close attention to the free play and my stock clutch was OK at 1800 miles. I still replaced the clutch with the Torq Drive from Rekluse and on the first ride I was adjusting the free play quite a bit. I seemed to keep losing free play for awhile-maybe because the fiber plates were getting soaked with oil and expanding a bit? It finally settled down though.
    #34
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  15. windblown101

    windblown101 Long timer Supporter

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    Loss of freeplay in a clutch system that pulls the pressure plate away from the clutch pack with the lever as found in the 790 would normally be associated with wear or in your case perhaps just the new clutch settling in.
    #35
  16. braaap!

    braaap! Long timer Supporter

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    Agree!

    And I'm just being a (post) dick because it's friday and tomorrow I'm riding to thrash my clutch foreplay. I mean free play.
    #36
  17. justinope

    justinope Long timer

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    FWIW I checked mine regularly and still encountered the issue. I also never noticed any slipping or changes in clutch behavior until the excessive heat symptoms / corresponding clutch feel that caused me to bring it into the dealer.

    As an aside though- I really don't appreciate people being KTM apologists about this situation.. sorry to be blunt but this unsubstantiated shifting the blame towards owners on a machine that should be (over)built to take a beating is rude to your fellow riders and IMO detracts from the overall conversation since KTM should, at the very least, feel compelled to investigate it further especially on a new model year bike. I didn't make it to high mileage on quite a few bikes now (without premature failures) by accident- it was through proper maintenance by either myself or the dealership (if I didn't have time). I will 100% admit to not loving to wrench on my bikes, but that shouldn't make me guilty of my stuff torching itself. KTM might think it does, but you'd think other riders would understand that at the very least. Seen it on here and facebook groups both now and it really irks me.

    Putting it differently- even if you think its user error like KTM does, how many other bikes out there have had similar "fragile clutch" issues?
    #37
  18. windblown101

    windblown101 Long timer Supporter

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    The jury is still out and in the meantime folks are going to have various opinions and theories. At this point an opposing view is just that. It has not been proven right or wrong.

    Like you and many others I haven't ever felt the need to replace a clutch pack so early and I've ridden a bunch of miles on and off pavement on a variety of KTMs and other makes as well.

    I do suspect the clutch on the 790 is a bit more susceptible to damage than average or that there is a production variance possible simply because of the number of reports of clutch issues compared to any other bike launch I can think of. That doesn't rule out the possibility that with a bit more awareness that it becomes a non issue. Time will tell.
    #38
  19. Toddv

    Toddv Been here awhile

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    Nobody is saying they are happy with the way KTM is responding, I think their response is shitty but it's a typical response for a corporation in such a situation, it's called loss prevention. What us folks are doing is using our mechanical experience and knowledge to try to figure out why this is happening to prevent future failures, especially on our own bikes. None of us want to be in your position I can assure you. I'm an ASE master tech and have been a technician for over 30 years and specialize in diagnostics. I'm a problem solver... I never said your failure was your fault, only that there may have been signs that something was wrong before it was caught, something or some way for the rest of us to detect and catch the problem before it becomes catastrophic. This way we can know what the actual cause is, something that will benefit everyone.

    Most clutches will just slip until they have no more grip without exploding, they basically bottom out before going metal on metal due to the loss in plate thickness from loss of friction material. The heat you were feeling was almost undoubtedly generated from undetected slippage (friction) but when the clutch plates broke it made it hard to determine what was wrong in the first place to cause it.
    #39
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  20. Thumper Dumper

    Thumper Dumper Been here awhile

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    Installed my Rekluse RadiusX clutch and measured the old one.
    Plates in perfect condition with no wear. Springs measure 48,2mm.
    My manual says minimum length is 48mm.
    I’m not heavy on the clutch and haven’t done any extreme off road and only have 3500km on the bike.
    25569A9A-6035-4F91-ADBE-1D228BB8DCEE.jpeg
    #40