KTM Duke 390 - Does it have to be hot to ride?

Question

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.

Answer 1

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.

• YouTube video showing the issue with a cold engine

• Unresolved stall issue on a KTM 390 forum

• Forum post where OP has the issue with a brand new vehicle

• A bunch of people saying 'me too'

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.

Answer 2

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.

Answer 3

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.

Answer 4

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.