2000 KTM 640 piston/barrel

Discussion in 'Thumpers' started by greasyknuckles, Sep 30, 2020.

  1. greasyknuckles

    greasyknuckles n00b

    Joined:
    Sep 29, 2020
    Oddometer:
    2
    Location:
    Bredasdorp, South Africa
    Good day fellow riders

    I apologize to any mods if this question has been answered in another thread. I did go through the index and found nothing that answered my pretty specific question.

    I bought a 2000 KTM 640 Adventure 2 months back with 37800Km's on. It is visually a used but not abused bike and the price was not bad. Before I bought the bike I did some research on which model years gave which problems and all that common issues.

    Naturally the bike started making a sound I did not recognize one day on a short trip. I immediately thought that I have delayed the preventative maintenance (main shaft ball bearing to roller bearing upgrade) one km to far and stopped and had the bike picked up. The next day I started stripping the engine covers on both sides and drained the oil and low and behold, filings.

    I inspected the famous ball bearing and expected the worse but was, at first, glad to see the bearing in good condition and fully intact (still going to replace it while the engine is disassembled). It quickly dawned on me that a intact bearing means the problem is elsewhere.

    Long story short completely stripped the engine and found that the conrod had play on the crankshaft and that the piston and cylinder has been badly grooved. I have attached photos of the barrel and the piston.

    I have read all the info I can on rebuilding these LC4's but cannot find a answer to my specific question(s).
    I understand that there is basically two ways of repairing the cylinder;
    1. Face the cylinder wall and re-plate it with Nikasil.
    2. Bore out the cylinder and insert a steel/iron sleeve.

    I am a student thus having a small budget. I would like some advice as to what method would be the most inexpensive considering how the bike will perform afterwards as well. I will be replacing the conrod as well as the piston and all the goodies with it. If it happens to be to re-plate it where can I have the cylinder faced and re-plated in the Cape Town or Mosselbay area?

    Feel free to ask any other questions you may have.

    Thank you for all the advise and knowledge I have already gained from this forum and you good posters out there ( Creeper and Laramie).
    Thank you in advance for the advise and help.

    Attached Files:

    #1
  2. NevBlu

    NevBlu Been here awhile

    Joined:
    Feb 1, 2014
    Oddometer:
    312
    Location:
    Carson City, NV
    Yes the piston needs to be replaced and cylinder honed at a minimum (replating is preferred). My rebuild post may help you, however sourcing machine shops and parts will be in your court. Good luck.
    #2