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My motorcycle, a KTM Duke 200, while riding is producing varying acceleration. This is during a single ride. For about a few minutes, the acceleration is alright, then after a few minutes, the acceleration seems to drop. Once I turn off the bike at traffic, and I start again, the acceleration seems normal. After a few minutes, the problem occurs again.

  1. The fuel is not a problem, as I'm refilling high grade fuel, which I've been using from a long time.
  2. I've checked out the air filter and I clean it thoroughly. In fact, even changed it to just check if that was the issue.

So what might be a problem? Am I looking at anything major?

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  • Does the turn-off-turn-on fix work when the engine is hot?
    – Zaid
    Feb 29, 2016 at 17:35
  • What year is your Duke?
    – DucatiKiller
    Feb 29, 2016 at 17:40
  • @Zaid - Yeah. It works. But for like two minutes or so.
    – Iceman
    Feb 29, 2016 at 17:51
  • @DucatiKiller - It's a 2013 one. She's clocked 30000 km.
    – Iceman
    Feb 29, 2016 at 17:52
  • Carburetor or fuel injection version?
    – DucatiKiller
    Feb 29, 2016 at 17:54

2 Answers 2

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Since this is a fuel-injected bike, this sounds like an air-fuel mixture problem.

Air-fuel mixture problems arise when the mixture is either too lean or too rich. If bad enough, both can result in poor acceleration:

  • In lean mixtures, there is too much air and/or too little fuel

    Typical causes for this include an intake leak which is allowing unmetered air, malfunctioning MAF/MAP/lambda sensor and partially-clogged injector.

  • In rich mixtures, there is too little air and/or too much fuel

    A stuck-open injector, over-pressurized fuel line, under-reading MAF/lambda sensor could cause this.

The temporary "restart" fix makes me suspect a bad lambda sensor; it's quite common for vehicles to run in open-loop mode for a couple of minutes. Assuming this is a narrowband sensor, you could confirm that it is working as it should using the test outlined here.

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  • This sounds more like fuel starvation to me rather than lean.
    – DucatiKiller
    Feb 29, 2016 at 19:48
  • @DucatiKiller isn't that the same thing?
    – Zaid
    Feb 29, 2016 at 19:53
  • I've always, right or wrong, differentiated the two between a fuel system delivery issue between the injector and the pump and a lean condition from unmetered air or a mapping issue of some sort. Perhaps I'm splitting hair but that's just how my mind has segregated issues over time
    – DucatiKiller
    Feb 29, 2016 at 19:55
  • A lean condition may be caused by fuel starvation, but isn't the only possible cause. However fuel starvation will always cause a lean condition...
    – Nick G
    Feb 29, 2016 at 21:40
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It may be something with the ignition system. Check the spark-plugs. This tends to happen if there is dirt or some type of gunk on a spark plug.

Might be worth checking the throttle position sensor.

The fuel system may require cleaning with some Seafoam or some liquid cleaner that works well with cleaning fuel systems.

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