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[Locked] KTM problems

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Kannnicht Tausend Meter, Jul 10, 2012.

  1. Hello

    I've a KTM 85sx, and it's turned out to be a real pain in the arse...

    Most of the time, it won't start.

    What happens is that the spark-plug gets very easily fouled. I've tried all sorts of oil-petrol mixes, but I think the bike has a far serious problem.

    Maybe it has something to do with the fuel to air ratio?

  2. Are you revving it hard enough? Many 2 strokes foul when they're not thrashed.

    Stick to the mixture specified in the manual and look elsewhere.
    Air cleaner dirty?
  3. It's not being thrashed all the time (trail riding).

    I'll check the air filter
  4. have you the right grade spark plugs in the bike?? do you have good spark when you remove them from the motor?? do you clean the spark plugs after they get fouled ? then check if they have good spark before you reinstall them ?? have you messed around with the air mixer screw on carb ?? and YES stick to mixture specified by manual .. after you start the bike how long until the plugs foul??,
  5.  Top
  6. I too have a KTM85 sx (2005 Model), it was fouling plugs like no tomorrow, I would have to carry several plugs just to get through a day at the track, even tried Iridium plugs.

    I messed with Fuel/oil ratios.... everything from 32:1 to 55:1 but still fouled plugs. (now run 37:1)

    I too thought the young fella wasn't ringing it's neck, so I'd jump on it and flog it... but still fouled plugs.

    Finally: took it to KTM Wodonga... the bloke knew exactly what the problem was... as fouling plugs constantly, is the tell tale sign the the 'Stator' in buggered. He replaced the Stator... I have changed the plug once in the last 2 years.. =D>


  7. Mate, this is déjà vue.

    Would you mind me asking how much it cost to fix?
  8. lol at your username.
  9. The Germans have it spot on...

  10. Fully fitted: it cost me $500.

    but if you are mechanically minded; you may be able to do the work yourself.
  11.  Top
  12. Hi
    I have a KTM 85sx.

    Spark plugs are very easily fouled. I found that two or three spark plugs were needed to get through a day of riding. This wasn't just a case of not riding hard enough, even while flogging it they seemed to foul.

    I was told that perhaps my Stator (generator) was buggered and was giving a weak start. (See https://netrider.net.au/threads/ktm-oil-problem.133619/)

    Today I pulled the bike out again. After a few kicks there is turnover, like she's starting, before dying in a few seconds.

    Most kicks there is exhaust coming out the back end. I wonder - Where there's smoke there is fire, right??

    A few years back we had the muffler packed tightly to keep the beast quiet. Maybe this is preventing a start?

    Do I have a problem with my stator? Or my muffler? Or both?

  13. check your spark out by pulling the plug and earthing it on the side of the engine. It should be a strong blue spark.

    I'm betting it is carbie problems however.
  14. I just tried with a new spark plug AND aerostart with no luck.
  15. You still need to test for a good strong spark as ibast has explained.
    If you have good spark, then look at fuel.
  16. OK, so now it's either fuel or air, fuel is most likely. Why didn't Aerostart work though? Does it have good compression?
  17. Do a plug chop. This was more standard road racing practice in the 2T days but no reason it won't apply to an MX engine.
    Find a place you can wind it up to flat out in top. Quickly close throttle, pull clutch lever, hit kill switch and coast to a stop.
    Pull the plug out and look at it. What colour is the ceramic around the electrode.
    It should be light brown. Black is too rich, white too lean.

    As a suggestion, over time engine vibes can wear the needle valve on the carb float bowl, causing the float level to run high and the bike to run rich.
    If the needle valve has a step worn in it, it's cactus.
  18. does it have reasonable compression ?
    worn piston rings/bore?
    Is there a possibility that you have broken a piston ring or had a mild seize and nipped a ring in the groove and/or scored the bore?
    low compression would cause starting difficulty.
  19. How can I check for compression?
    I have had people say the stator can cause fouling in these bikes
    And that would explain the start up issues. Maybe there is a weak spark but not consistent

    I had my muffler packed tightly to reduce noise. Could having I too right foul it up and make it hard to start?