The only problem I’ve ever had with a KTM was when my Super Adv’s front tyre deflated slowly on day 4 of ownership. It was a badly fitted spoke/tubeless tyre gasket, but they sorted it out in 24 hours and gave me a £200 credit note for the inconvenience 🙂
Apart from that, problem free (touch wood) since 2015 for the Super Adv and 2021 for the Super Duke GT.
You can buy my Super Adv, if you like 😉
As a brand, I’ve only heard of problems with the smaller engined stuff that gets used off-road a lot, but most of those are usually used quite hard. The 1290 LC8 engine is a mechanical marvel and truly one of the greatest bike engines ever made. 175bhp and 106lbft torque (80% of which you get at just 2500rpm). I only have to quietly blip the throttle when the lights go green and I’m 100 yards ahead of all other traffic. It’s quicker to 150mph than a Ducati 1299 Panigale or BMW S1000RR sports bike. But they’re also very well behaved/usable/comfortable on road too. Sports touring with the best of both worlds (and words).
Having said all that, they depreciate faster than a Ducati or BMW, but the salesmen aren’t as welcoming as BMW. Parts and servicing are a fair bit cheaper, though. It’s like they build them so you can cheaply replace the bits that they know will wear out/take abuse. Looks can be a bit Marmite for some people, but I like them, and I like having something a bit different. Handling - I’ve never felt more in sync with a bike than the Super Duke (better than ’Blade or S1000RR on road, probably on track too).
If you’re serious about buying one…
KTM seem to come out with a new version of their bikes every two years (like clockwork - must be the Austrian heritage), though Covid has bucked the trend this year. You can almost always save big bucks buying a brand-new-but-old-stock bike when the newest model arrives. My 2020 Super Duke GT was £4K cheaper than the model that replaced it and was the exact same bike apart from the exhaust going from Euro 4 to Euro 5 regs. Pre-2020 GTs are a gen1. Mine is gen2 and they improved it a lot over the original but the 2021 update isn’t worth having until the gen3 arrives (but even then, maybe not - I expect the same as the latest Euro 5 model but with their adaptive cruise control auto radar system added). Any KTM is definitely worth a test ride, though.