There has been a few clutch failures, at fairly low mileage, and the people affected have been quite vocal as very few of the failures have been covered by KTM. The numbers of failures is however very very low. Since I wrote this article, in November 2019, the number of clutch failures stayed really low. There were 6 known at that point, and this number didn't even doubled since then. At this point this is a very rare occurrence. I'll update this article if I receive more updates.
Reports of failures
The main post triggering the attention to the issue was Quintin Mclaughlin's report: he had only just run the bike in and had the initial service before setting off on a road trip through France, Spain and Portugal. Clutch failed at only 2,000 miles (3200kms).
On the comments on this FB post there are other report of failures: Uli Schildt picked up his bike in Arizona and rode 3,000 miles back to Washington State. A week later his clutch failed.
JP De Villiers, still on the same FB post, writes, "After my first clutch burnt and the fault was put on me after only 2700 km. I put a Rekluse torque drive with the hope it will be a stronger replacement. It took exactly 300 km, clutch started taking high and slipping exactly like before."
Those were simple failures, where replacing the clutch plates and the spring was enough to go back on. Unfortunately some riders experienced more catastrophic failures requiring a 3k "rebuild of the engine". Bill Cairns was the first one, but Yevhen Karel described a similar failure on this FB post : "the clutch plates were burnt, broken into pieces. Then clutch powder blocked the oil filter, oil pump, etc. and the oil could not circulate as it should (the oil could not be seen in the check window). As a result, some oil has been found in the exhaust. Now the engine needs to be rebuilt, cleaned and new clutch to be installed".
There is another report from Mark Ferbrache's of a failure at 9000 kms, still on the same long FB post. But in this case note that Mark uses the clutch a lot: " you're on the clutch the whole time. Plus if you're on a really narly climb your going to be on the clutch a lot". As opposed to a small trial bike, slipping the clutch all the time on a big adventure bike is going to cook it in no time.
Alarmed by the news of clutches failing, windblown101 decided to open his, just to check, and found it in working order. He still changed the springs as they were slightly out of spec. So here you go, pics of a good clutch.
I leave the last word on this to gearheadE30: "Clutch failures (unconfirmed). Probably similar to range of experiences people had with 950/990 clutches. From what I have seen, most of these failures have been from abuse. I have only seen one that actually looked like a surprise failure, which appeared to be due to insufficient oil flow. The outermost clutch few clutch plates and fibers didn't seem to be cooling adequately and showed obvious signs of heat. Seems to be fairly uncommon but we may see that the "meoni clutch mod" from the 950/990 becomes a popular change. One also looked like clearance between the input shaft shaft ID and the clutch release "tension bolt" part number 63532048104 was maybe too tight and not letting oil through to lube the clutch...but that was just from looking at wear patterns in pictures so it is hard to say. I'm calling this an open question, but it's worth saying that the clutches held up great in Morocco and the only problems we had were due to unusual abuse".
What we know about the clutch
The clutch on the 790 is a wet design, but instead of just dipping in the oil a feed is also injected via a jet in the center of the clutch shaft. This jet is on the worklist of recommended work to be performed at every service (See the Service manual, page 414). Note that this is not a new system for KTM, the same overall design has been present on older models like the 950.
Some believe that those failures are due to the jet being blocked by debris in the oil, preventing lubrication of the plates and causing an early failure of the clutch. A KTM dealer even diagnosed it as such. There are suggestions to increase the jet size, and/or drilling holes in the basket, but those are not proven to actually work (The fact that it worked on the 950 16 years ago, doesn't make it the panacea for a brand new bike). Plus increased oil flow will make finding neutral more difficult. See also this post with good information about pressure and the size of the hole.
Recommendations
The #1 recommendation is if you feel the clutch slipping, stop ASAP. From first sign of slippage to unusable bike seems to happen in a very short time.
Check the freeplay. Often. Lack of freeplay at the lever will cook a clutch fairly quickly: make sure to control it (procedure is in the manual). For those using a CamelADV extender, to keep the same freeplay on the clutch you need to make the freeplay on the lever a little longer.
Finally when the traction control intervenes and leads to the engine bogging down it's important not to slip the clutch to raise revs, instead you should leave MTC to do its job.
Wear item
The clutch is a wear item. As such, like brake pads or tires, those failures are not covered by any guarantees, including the KTM one. For this reason none of the failures above were covered, to the dismay of the owners.
Some believe there is a technical issue with the bike causing the early failures, and if it is the case, the clutch should be changed free of charge, along with the cleanup job to remove bits of clutch material from all the oil passages.
Acknowledgment
I was kicked into gear into writing this article thanks to Tim Cullis. He posted another great post on an UK forum, which served as the original base for this article.
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