I have a KTM Duke 390 - 2013, single cylinder 373 cc motorcycle for 4 months now. I bought it from another owner when it was around 9500 km. now It's at 12000. This is my first bike, and I'm trying to improve my abilities, technical and theoretical knowledge about the bikes too.

For the last month-when winter got really harsh here-my bike started to behave differently. Especially in the mornings I start the engine, and immediately start riding without warming it up. And at the first stop at a traffic light no matter I'm on neutral, or pulled the clutch lever fully while on first gear the engine stops, and won't start for 10 to 15 minutes(bump-start works). Very very annoying behavior. In order to avoid this, I don't let the engine to run idle(always give some gas up to 2500/13000 rpm - its idle is 1500 rpm).

Interesting point is when I took it to KTM service they said:

"This is a normal behavior of single cylinder engines. You have to start it on neutral, warm it up at least 4-5 minutes. Than you're good to go. Otherwise it will stop and won't start for a while."

I took their advice and it works just fine. But I'm struggling to be convinced. I am planning to sell my bike around spring, and I don't want to put up a faulty bike for sale without knowing it's fault.

Do you guys think that this behavior is common and normal? Or should I dig deeper.

PS: My bike is still on warranty.
  • Did your issue get fixed? Commented Dec 22, 2015 at 21:43
  • Well, my bike got out of the service before I post this question. They said they've updated the ECU, and nothing's wrong with the bike. Since then I always warmed it up, and no problems. Therefore I cannot exactly tell if it is still same, or ECU update fixed the problem. But warming up is working, and making the first minutes of the ride much smoother. Not sure if I can call it a fix though :) Commented Dec 22, 2015 at 23:35
  • there's quite a few vid's of guys riding and pulling in the clutch and the bike stalls. This is after the motor is at operating temperature. Would be an interesting experiment to see if yours does that. Hopefully no more problems :) Commented Dec 22, 2015 at 23:37
  • No mine was doing it only when it got just started. After a few minutes it was fine even before. Commented Dec 22, 2015 at 23:57

4 Answers 4


Pretty Common Problem with the Duke 390

This is a very common issue with the KTM 390.

There are dozens of posts regarding customers who are experiencing the same exact issue. Additionally, there are a few YouTube video's that show the problem happening pretty consistently.

The various proposed issues related by customers seem to revolve around these theories in particular.

  • The bike comes with ECU programming that is too lean.

  • This is an innate issue with single cylinder larger bore motorcycles and can't be fixed.

  • A loose connector to the ECU

  • A dirty throttle body

  • A dirty fuel injector

  • Faulty ECU

  • Inadequate fuel pump pressure, faulty fuel pump

  • Faulty side stand switch

  • Faulty tip switch (kills engine when bike falls on it's side)

Here is a list of URL's from OP's on various forums.

Additionally, there are plenty of reviews from motorcycle magazines where they complain of the same exact issue.

Apparent Fix

There is a claim that the true fix is an ECU update. The justification was that the ECU had a map that was too lean.

Here is one post.

Confirmation I also called a friend that works at a local KTM shop. He indicated that there is awareness to the issue and that there is a service bulletin from KTM to update the ECU as well as set the idle 100 RPM's higher.

If it's under warranty the dealership should be aware of this and be able to resolve it without an issue.

please note that I called a US dealership, KTM is notorious for not releasing service bullets internationally

Additional Thoughts

I have seen this type of issues with dozens of bikes including my own. Most common fix was the ventilation hose being bound up and incorrectly routed so that when the tank was sat on the bike, the hose pinched. After riding for a few miles a negative pressure would buildup in the tank and the fuel pump couldn't overcome the vacuum.

I have also routed a breather line that was touching the exhaust and the hose melted, preventing it from being able to breath.

Thumpers and Stalling

I do not agree with the idea that single cylinders are prone to this. I have had 6 single cylinder 4-strokes. Some of them had a stalling problem, some did not. I was able to fix all of them. Issues ranged from bad fuel pumps to clogged ventilation breathers for the gas tank to air leaks or lean conditions.

I believe the thumper stalling idea is a myth that get's perpetuated. Certainly there are some models that may have an issue, just like this bike but I do not see this as a single cylinder issue so much as a KTM quality control issue in there manufacturing process.

Warm Up

All of the above being said I would still warm up the bike on cold mornings. The ECU will kick up the idle for a bit more oil pressure while it warms. Although not an air cooled engine parts still expand during warm up AND the oil get's thinner as the bike get's up to operating temperature. Also, I try not to drive vehicles until they are off choke. Old air cooled engine/carburetor habit that I believe still applies to more modern FI (fuel injected) vehicles.

  • 1
    +1 for "I do not agree with the idea that single cylinders are prone to this." I was wondering why a single cylinder 4-stroke would suffer from this. Agree that it might be more of a design issue than something inherently theoretical
    – Zaid
    Commented Dec 21, 2015 at 20:55
  • I'm wondering out loud here.. It seems like this model is suffering from a lack of cold-start enrichment. It would tally with the "ECU reflash" fix
    – Zaid
    Commented Dec 21, 2015 at 20:58
  • @Zaid agree that's an issue/fix combo. The other weird thing is that there are youtube video's of guys riding with a gopro and they pull in the clutch while coasting at almost any speed and the engine dies. My buddy indicated that they are related in a sense that they are both fuel map issues in the ECU Commented Dec 21, 2015 at 21:01

Firstly This is common on high capacity single cylinder engines where the compression ratios are very high compared to relatively sized multi cylinder engines.

I have ridden a KTM 390 and I have faced this issue sometimes, getting it to restart is a pain, trust me its normal behaviour there is no fault or issue with the bike, its just the way the bike is designed.

What you can do is after starting, either idle or drive at very low speeds for a couple of minutes and then you are good to go. I would say at least 3 or 4 miles.

PS: This issue also persists when the engine is very very hot.

  • Thank you, it's good to hear this :) So warming it up at start works for my problem. But you are saying it can happen when its too hot too, what is the approach to avoid that? Commented Dec 21, 2015 at 14:05
  • Just Let it cool for a bit , like 10 minutes and then start again, KTM said they have fixed this issue by increasing the ON time and trip off time of the radiator fan so that it does not overheat for the 2013 model onwards. Not sure if your bike is the new one, If you had not gotten that issue yet then i think you need not worry plus where i live we have constant outside temperature of 110 degrees to 120 at peak times so that also contributes to the issue. We actually dont have much of cold start issue so to speak off compared to European countries. :-)
    – Shobin P
    Commented Dec 21, 2015 at 14:08
  • Waow, it's pretty damn hot. Well I haven't ridden it more than 150 km a day. So I'm not sure if it is okay or not :) But now at least I'll know why it happens :) Thanks. Commented Dec 21, 2015 at 14:12
  • You can go beyond , The Bike can Handle it, KTMs are actually pretty good for colder climates you should not have any heating issues like we do.
    – Shobin P
    Commented Dec 21, 2015 at 14:28
  • :) I'll see it in few weeks. I'll be going to a 400km ride and coming back at next day. We'll see how it handles. Commented Dec 21, 2015 at 14:41

Its always good to warm up a engine before a throttle -away -to glory. I keep my ktm idling for 2 mins and then constant throttle at lower gears when i start off i dont ride it above 50kmph for the first 10 mins. I keep it in 3rd gear. And once optimum engine temperature is acheived i resume natural riding. This has worked for me. Also, if u r into an habit of shutting of bike the moment u stop, then just leave him idling for a couple of seconds so that the cycle is disinteruppted.

  • upvoted you so you can get some rep and function better in the site. Seems like you are fellow lover of motorcycles. Cheers, see you around. Commented Jan 20, 2016 at 4:24
  • True story. I understand 2 wheels better and know a cent. This forum has helped me so much about the other greener side. Thanks mate.
    – Seeker
    Commented Jan 20, 2016 at 5:56
  • This may be true in the case of a KTM with fueling issues, but in general for engines it is not. It's best to drive an engine normally on cold startup. Oil is fed better at above-idle RPMs than at idle. In fact, many motorcycle mfgs recommend to never idle the engine for > 10 mins.
    – justinm410
    Commented Sep 27, 2016 at 18:10
  • For carbureted bikes you'll want them to warm up more but on a fuel injected machine you're good to go as soon as you're ready after it's started. On a very cold day I will sometimes wait for the temp gauge to show a value other than 'LO' but otherwise start up and roll out.
    – Nathan V
    Commented Sep 27, 2016 at 19:30

I think this is a very common issue with the 390. It is clearly running very lean when cold for whatever reason. I won't speculate as to why, but it does not seem to ever be "fixed" as far as I know.

I have an RC390 and every single 390 owner I have talked to has this issue. I have seen many ride off from parking spaces and "pop" when they open the throttle and stall within seconds. (Almost all will have issues restarting after this pop, but the bike will eventually start again) I have Power Commander and the previous owner had the bike on a dyno and it still does this.

The bike starts fine almost always the first time and then you just need to keep it rev'ed just enough to stay running till it warms up. Took me a bit to figure out how much throttle to give it when cold (not much) to not rev it too much but to keep it running. (rev'ing a cold engine is bad). Opening the throttle quickly and too much when cold is a sure way to stall my bike. Once I sorted this out, it has not really been a big problem.

I have other single cylinder motorcycles (FI and carb) and they are all a bit more finicky than my multi-cylinder bikes when cold, so perhaps the time it takes for that piston to come back around twice and fire again gives the bike more time to stall. But it actually never really occurred to me before seeing it stated here, so not really a huge thing.

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