Clintnz's KTM 640 95,000km service

Discussion in 'Thumpers' started by clintnz, Nov 1, 2010.

  1. clintnz

    clintnz Trans-Global Chook Chaser

    Joined:
    May 17, 2004
    Oddometer:
    3,614
    Location:
    Rotoiti, New Zealand
    I was hoping to get to the 100K km mark but it was not to be, the metal on the sump bungs when I went to do a service last night confirmed that I wasn't just being paranoid when I thought the ol 640 was rattling a bit more than usual. :cry

    [​IMG]

    But hey, what's this sitting on the workbench? :D

    [​IMG]

    Luck would have it that I had just taken delivery of a big batch of parts, cheap from the USA c/- a friend who has just been over there. So I decided to tear into it. Starting a thread to detail the process seemed like a good idea so I can remember how it goes back together & maybe some of the engine & LC4 gurus on here can stop me doing anything stoopid.

    I wanted to get the top end off asap so I could check the bore & find out which piston I have (I or II) so I can order the piston kit, the last major item I need (I hope) None in stock in NZ so that will be a 3-4 week wait.

    The good news is that the cylinder looks OK. I brought it into work today & the workshop foreman measured it up with an internal micrometer, 101.00 mm everywhere. There is some scuffing but maybe not too bad? None of the marks can really be felt, What say the experts?

    [​IMG]

    [​IMG]

    [​IMG]

    I didn't have the camera at home last night so I will get more pics tonight along with some measurements of wear on the parts I have dismantled so far.

    Cheers
    Clint
    #1
  2. clintnz

    clintnz Trans-Global Chook Chaser

    Joined:
    May 17, 2004
    Oddometer:
    3,614
    Location:
    Rotoiti, New Zealand
    Anybody know anything about cylinder bore surface roughness? I've got a wee gadget that I use at work for measuring roughness so I thought I'd run it over the cylinder while it was sitting on my desk. It would only fit in sideways so the below readings are taken in the direction of piston travel, 1/2 way down the bore:

    Back wall (worn area) Ra = 41 micro inches
    Cam side wall (non worn area) Ra = 33 micro inches.

    I have Rz numbers & metric equivalents too if anyone is interested.

    Cheers
    Clint
    #2
  3. gunnerbuck

    gunnerbuck Island Hopper

    Joined:
    Nov 19, 2005
    Oddometer:
    4,383
    Location:
    N.V.I, B.C.
    I see you have a new con rod kit... Those fine wear lines on the front and back of the cylinder could be an indicator that the old one is starting to go....

    A light hone should fix that up...

    Did you check the ring end gap,old VS new rings?
    #3
  4. Phreaky Phil

    Phreaky Phil Long timer

    Joined:
    Mar 18, 2006
    Oddometer:
    1,940
    Location:
    NEW ZEALAND
    :lurk :lurk :lurk :lurk
    #4
  5. clintnz

    clintnz Trans-Global Chook Chaser

    Joined:
    May 17, 2004
    Oddometer:
    3,614
    Location:
    Rotoiti, New Zealand
    Yep, I think there is a good chance that the metal flakes on the magnet are from the big end, there didn't seem to be much radial play just wiggling it but the rod could be rocked side to side a fair bit.

    I'm going to measure the end gap & piston wear tonight, the piston & rings certainly looked due for replacement. I'm also going to take apart the rocker assembly, it will be interesting to see how much wear there is on the inlet roller bearing.

    Cheers
    Clint
    #5
  6. Tseta

    Tseta Lost

    Joined:
    Nov 30, 2008
    Oddometer:
    674
    Location:
    On the road
    We are getting many great rebuild threads here this winter!

    :wave

    [​IMG]

    In the '98 engine I'm doing, the rod does move side to side surprisingly much. However, the specification for axial play is as great as 1.0mm. Try it with a feeler gauge, it probably is within spec. The radial play is a different animal, I have no idea how to measure that.

    Cheers,

    Tseta
    #6
  7. benno.h

    benno.h cageracer

    Joined:
    Aug 14, 2010
    Oddometer:
    437
    Location:
    Brisneyland, Arse-Trailer.
    Hey mate,
    could you elaborate on this rod issue?

    I've been having some issues with my XR and the machinist reckons the rod may be at fault.
    #7
  8. Mark_S

    Mark_S Fair Weather Faggot

    Joined:
    Jun 13, 2007
    Oddometer:
    2,095
    Location:
    Kapiti NZ
    hope you get this all buttoned up before the Burt

    will be watching with interest
    #8
  9. gunnerbuck

    gunnerbuck Island Hopper

    Joined:
    Nov 19, 2005
    Oddometer:
    4,383
    Location:
    N.V.I, B.C.
    I have taken small engines apart with failed con rods and they often display piston cylinder scoring... I can only guess as to what exactly takes place to cause this but I would think that the vertical slop in the shot rod bearing causes the piston to rock back and forth at a much more accelerated rate than normal....
    #9
  10. Rosie!

    Rosie! Little MissAdventure

    Joined:
    Feb 25, 2006
    Oddometer:
    464
    Location:
    Rotorua, NZ
    Sadly the 640 won't be going to the burt :cry
    He's had to revert to plan six-hundred-and-ninety :evil
    #10
  11. JensEskildsen

    JensEskildsen Long timer

    Joined:
    Mar 24, 2009
    Oddometer:
    1,086
    Location:
    Denmark
    Looking forward to you're progress.

    How is the servicehistory for the bike looking? Any "major" work done previously?
    #11
  12. clintnz

    clintnz Trans-Global Chook Chaser

    Joined:
    May 17, 2004
    Oddometer:
    3,614
    Location:
    Rotoiti, New Zealand
    Hi Jens, you are right, I should give some history of the bike. I bought the 640 new in April 2004, it was a run out 2003. It has been serviced to the recommended schedule from new, by the local KTM dealer for the first 12 months & then by me since then. On the rest of the bike I have had the forks & shock serviced a couple of times each, replaced all the wheel bearings a few times & done the steering head & rear linkage bearings once or twice. I have welded up a crack in & reinforced the rear subframe last year.

    I have done the common minor jobs on the motor over the years; re sealed the cam cover, replaced the countershaft seal & o-ring a couple of times & replaced the starter sprag clutch. At 50 000km I replaced all the cam & rocker bearings, rebuilt the water pump & replaced the cam chain. The only part showing excessive wear at that point was the inlet cam follower roller bearing.

    Cheers
    Clint
    #12
  13. clintnz

    clintnz Trans-Global Chook Chaser

    Joined:
    May 17, 2004
    Oddometer:
    3,614
    Location:
    Rotoiti, New Zealand
    Trouble is, it's the start of summer here :umph Luckily I have plan #690 in place for the next ride. :evil

    The play in the conrod I was referring to is the movement of the top of the rod through an arc side to side.

    Anyway, back to the used 640 internal engine parts porn:

    Some carbon on the piston, but not too much:

    [​IMG]

    The skirts are well worn, but not too deeply:

    [​IMG]

    [​IMG]

    The most worn part of the piston skirt measured up with my cheap but fairly accurate calipers at 100.80mm. With the bore at 101.00 this gives a clearance of 0.20mm vs the max spec in the manual of 0.12mm.

    The end gap on the top ring was 1.04 & the mid ring was 0.64mm vs the max spec of 0.80mm. The oil ring was 1.25mm vs a max spec of 1.00mm, so well due for replacement.

    It's worth noting that despite this wear the bike was not using much oil, maybe 2x 100-200ml top ups between 5000km services.

    I pressed out the cam follower rollers & they were in fairly good shape, especially compared with the wear I found on the old inlet roller shaft back when I replaced these at the 50 000km mark.

    [​IMG]

    Then I stripped some more parts off the bike & gave everything a wash.

    [​IMG]

    [​IMG]

    Cheers
    Clint
    #13
  14. B-Rod

    B-Rod RubberNecker

    Joined:
    Jul 28, 2007
    Oddometer:
    2,012
    Location:
    Alberta
    Just pulled my rocker cover today, and at 30K, my rollers look pretty good. I can't recall, did yours fail at 50,000? I've read a couple posts where they failed at 30K, so I'm doing mine once the parts come in. Bummer about doing this at the beginning of the season. Must be only spring though, so you should be able to enjoy a fresh bike for the majority of the season.

    What con-rod kit and piston did you end up with? KTM or other?

    #14
  15. Jan from Finland

    Jan from Finland Registered

    Joined:
    May 2, 2005
    Oddometer:
    573
    I wouldn't have worried about that amount of metal. Assuming there are no big pieces of bearing casing or such. I have about the same mileage and the engine has been opened twice. Most likely the metal comes from transmission gears. Especially 4th and 5th gears do wear, if you ride too much at low revs.

    :ear
    #15
  16. clintnz

    clintnz Trans-Global Chook Chaser

    Joined:
    May 17, 2004
    Oddometer:
    3,614
    Location:
    Rotoiti, New Zealand
    Yep, it's not too bad, we ride year round here anyway, with the the peak of activity usually Jan - April, so I won't miss out too much. One of the reasons I didn't hesitate to tear into the motor was that my brother offered me use of his 690 for the 10 day trip Rosie & I have planned in 3 weeks, It'll be fun to give the 690 a good test out.

    My inlet roller hadn't totally failed at 50K km, but was getting close. I noticed the valve clearances opening up so in light of several reports of the rollers being an issue I opened up the head to replace them, the wear side of the inlet shaft was clearly worn & getting quite rough.

    I have the KTM conrod kit & have just ordered a KTM piston kit. There is a good chance that there is better stuff available but since there is zero data on long term reliability of aftermarket rods & pistons for these motors I decided to stick with what I know is capable of lasting another 95K km.

    Cheers
    Clint
    #16
  17. clintnz

    clintnz Trans-Global Chook Chaser

    Joined:
    May 17, 2004
    Oddometer:
    3,614
    Location:
    Rotoiti, New Zealand
    Yeah, if I hadn't had all the parts & the offer of a bike to borrow I might have run her a bit longer, but the next ride is going to be near 5000km & I didn't want to break down 2000km from home.

    The 640 used to always have a lot of fuzz on the bungs but for the last 20-30K km they have been a lot cleaner, so the sudden appearance of this really flaky metal plus the motor maybe sounding a little more rattly than usual made me decide to get stuck in.

    Cheers
    Clint
    #17
  18. crazybrit

    crazybrit Long timer

    Joined:
    Mar 16, 2006
    Oddometer:
    8,553
    Location:
    Portland, OR
    I like your logic. Looking forward to seeing how things progress.
    #18
  19. rogerh

    rogerh Adventurer

    Joined:
    Apr 5, 2008
    Oddometer:
    90
    Location:
    Hamilton, New Zealand
    Yep, the change on the sump plug would have me alarmed. Good call to rip into it I would say. Last thing you want is a catastrophic failure.

    Good luck and have fun. See you soon. Weekend maybe :evil.
    #19
  20. tdreyer

    tdreyer KTiM

    Joined:
    Mar 24, 2008
    Oddometer:
    508
    Location:
    Used to live in Crestview FL, now ????
    :lurk Really watching this one as I've just over 52k mi. on mine.
    #20