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Thread: New to the forum, LC4 640 questions

  1. #21

    Default Re: New to the forum, LC4 640 questions

    The attachment didn't work, not sure why. I looked in my manual though and see the tool. I can probably make one, if not I'll go ahead and buy it. So might be on hold for now... Sure hope I find a smoking gun when I get the cases split!!! lol.

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  3. #22

    Default Re: New to the forum, LC4 640 questions

    Click image for larger version. 

Name:	20200530_200733.jpg 
Views:	7 
Size:	62.4 KB 
ID:	38058Not sure why the attachments dont work, looked at them yesterday
    Last edited by ejr; 05-31-2020 at 09:22 AM.
    2005 450 exc
    1996 620 rxc
    1986 250 mxc

  4. #23

    Default Re: New to the forum, LC4 640 questions

    Thanks. I went ahead and found a puller on amazon I believe will fit, and it was pretty inexpensive. I have everything as far as I can get without pulling the flywheel. I did pretty good using automotive pullers, and other tools to get everythign apart lol. I should have the rest apart by next weekend. I found some axial play in the piston pin (a lot) and the connecting rod main/lower bearing (not a lot there). Not sure, may be normal. Also, the piston skirts appear scored. The cylinder walls are not though. Other than the axial play, everything seemed tight and there was no slop in the rotating assembly. Also, everything on the top end, cam, rockers, etc. appears fine.. The connecting rod bearing/bushing at the piston pin looks a little rough. I'm gonna try to upload some pics/videos.

    There's also some axial play in the mainshaft (think that's what it's called, the shaft the clutch is on). Again, not sure if normal or not.

    Is there a "main engine rebuild kit" available? With bearings and more importantly gaskets? Or do I need to order all this stuff individually?

    Main bearing (connecting rod to crankshaft) axial play:

    Connecting rod to Piston bearing axial play:
    Attached Thumbnails Attached Thumbnails 20200531_095701.jpg   20200531_104953.jpg  

  5. #24

    Default Re: New to the forum, LC4 640 questions

    Piston looks bad, that's got to be some or all of the noise.
    How loose is the skirt in the bore ?
    That " axial " play on the piston is normal I think.
    Every engine I have had apart had that. It should be tight enough so it has no
    Rotational play or any up and down either.
    That piston though has been lacking oil for whatever reason.
    There is a jet screwed into the case below the piston that sprays oil on it, make
    Sure it's not plugged. I think that side to side on the crank, connecting rod is normal
    Also. You have a repair manual yes? It explains all of that.
    Endplay in the crank itself is important I know for certain.
    The cylinders are pretty tough with the nakasil coating on them
    And can survive more than one pistons demise. If it still looks
    Good and measures in spec. It can be reused. Just be careful with
    Honing them out, you dont want to remove the coating.
    Last edited by ejr; 05-31-2020 at 11:10 AM.
    2005 450 exc
    1996 620 rxc
    1986 250 mxc

  6. #25

    Default Re: New to the forum, LC4 640 questions

    I couldn't feel any play in the piston when it was in the cylinder by pushing on it. Seemed normal/tight fit. But yeah that scoring certainly doesn't look normal. Not sure I can say though that that amount of scoring would cause the volume of shavings I found. At this point, doesn't really matter, going to replace anything that's looking suspect. Now I'll wait on the flywheel puller. I was able to use a ball joint splitter to pull the timing gear off the crankshaft. I'm thinking the universal flywheel holder tool I bought will also double OK as a sprocket gear holder. Should be able to get away with minimal special tool purchases.

    I don't really plan on replacing every bearing (unless I could find like a master kit that has it all). I just don't want to have to source all the individual parts. The odometer shows ~12,000 miles. I never checked when it still was operational, but I assume that's real and working. I know the bike sat for several years before my father in law got it, he had to do some work to it to get it running. Also, not trying to be argumentative, but to the person who said the head had been replaced due to the color of it, the owner's manual I have has the same bike on the cover with a silver engine and black head...?

  7. #26

    Default Re: New to the forum, LC4 640 questions

    There are examples of black heads on silver cylinders just by doing a search.
    Silver on silver too so I agree. Aluminum wouldn't stick to magnet so must be something else.
    Some shavings are not unusual thought. Some of that could be clutch related, probably about time anyway with 12000.
    That one mainshaft bearing that has been a problem I replaced but the one I took out was fine.
    Probably out in the garage somewhere.
    2005 450 exc
    1996 620 rxc
    1986 250 mxc

  8. #27

    Default Re: New to the forum, LC4 640 questions

    Is the piston aluminum?

  9. #28

    Default Re: New to the forum, LC4 640 questions

    Always thought so, but maybe not so sure now, does a magnet stick ?
    2005 450 exc
    1996 620 rxc
    1986 250 mxc

  10. #29
    KTMTalk Member
    Join Date
    Aug 2002

    Default Re: New to the forum, LC4 640 questions

    Check the cam lobes and rocker arm rollers and adjustment screws for wear. Replace the water pump bearings. There were many variations of those motors made by KTM with slight differences so it is best to order OEM gaskets for your model bike. Regarding the black head and gray engine. Our 2001 LC4 engine is all black and other models all gray. I do agree that there are pictures of engines that are gray and black but I am not sure if they are factory or not. OEM pistons were made by ELKO. If you buy an after market piston measure the cylinder bore to ensure that there is sufficient clearance.

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