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How to replace starter sprag on KTM 950/990 (LC8) - write up

Discussion in 'Dakar champion (950/990)' started by keener, Apr 5, 2014.

  1. gefr

    gefr Life is a trip

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    So the verdict is proven with three installations of the 640 sprag as is operating properly.
    Great findings.
    Cheers
    #41
  2. keener

    keener Speed changes you.

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    That's great news. I'm guessing the lip on lc8 version is only to hold the sprag in place during installation and disassembly? Can you confirm that?
    #42
  3. KMS6

    KMS6 Mountains and Motorcycles ...... and Hockey Supporter

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    I would agree, couldn't see any other purpose for the lip. The 640 sprag that I used still wouldn't pass completely through the hub, even with no lip, so it was pretty much the same situation. Once the sprag is in place in the hub, the hub is bolted to the rotor, and the rotor is bolted in place it didn't seem to me like the lip on the 950 sprag would serve much purpose.
    #43
    keener likes this.
  4. keener

    keener Speed changes you.

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    Transferring the beans isn't difficult, but regardless its good to know 640 part is a drop in!

    Without the lip, the sprag may get left behind when removing the assembly or fall out,... This must have an improvement to make assembly easier.

    One big advantage of using 640 housing is that if the sprag fails again, one won't need to take out the green loctited screws. That loctite is hard to find.
    #44
  5. arnix2013

    arnix2013 Arnix

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    Thanks for a very good write up. Helped me out a lot. But on first attempt it did not work as expected, started once and then failing - not same as original failure, all the beans were in a very bad shape.
    Taking it apart again showed that the free wheel gear had significant wear. Ordered a new one, part 60040020000, put it all together again. And now the engine sounds like never before in my history with the bike.
    A good advice might be to inspect the free wheel gear before putting it all together again.

    DSC_0252.JPG
    #45
    DistortedAxis, outbacktm and keener like this.
  6. gearheadE30

    gearheadE30 @LC8Adventures Supporter

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    For whatever it's worth, I've also done the 640 sprag swap and it's working great. I transferred the beans, though.
    #46
    keener likes this.
  7. Gadjeep

    Gadjeep Adventurer

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    Has anyone heard of having a shot sprag lock up the motor? I have an 04 950 Adventure and when I went out to start it on Saturday things got serious.

    I touched the start button and it sounded like maybe it made one revolution before a loud bang and no more starter turning. Subsequent pushes of the button got only a click. I put it in 6th gear and tried rolling it ahead but it only dragged the wheel. I then bumped it backwards a few times and it finally released. I then touched the starter again for just about 1 second and it spun over very quickly and made a clicking sound. That's the last I touched the starter.

    I pulled the generator cover and found no shrapnel so far and I'm now pouring together the tools to pull the rotor.

    Any info not already in the sprag write up would be appreciated. thanks
    #47
    rocky86 likes this.
  8. keener

    keener Speed changes you.

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    I can not think of anything else other than jammed sprag beans to cause this issue. Did you ever hear anything unusual in the past when starting the bike?

    In my case it made that horrifying loud sound during start once in a while before it finally gave up.
    #48
  9. Gadjeep

    Gadjeep Adventurer

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    Never anything horrifying but it did seem like the starter would kick out early at times requiring several stabs at the button. It's my first lc8 so I don't have much to go on.
    Thanks for the help!
    #49
  10. keener

    keener Speed changes you.

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    Yes that sounds like it.

    Take the generator cover of and then take the torque limiter gear off at the top. At this point if you hit the ignition ,your starter should spin freely. Do this so you can be sure you dont have any starter/relay... issues.

    If starter was fine, you can proceed to checking the sprag.

    Hoe many miles do you have on the bike?
    #50
  11. Gadjeep

    Gadjeep Adventurer

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    Yes, the starter is ok and turns freely. The bike has 54k mi and has never has the sprag serviced according to the PO. Still waiting on my rotor pulling tools but expect them tomorrow and hopefully get some time to work on it Sunday. Will be sure to update. Thanks again for the info and support. :beer
    #51
  12. Gadjeep

    Gadjeep Adventurer

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    So I pulled the flywheel, sprag and associated parts and unfortunately found none in bad shape. I'm afraid my issue may be deeper.
    #52
  13. keener

    keener Speed changes you.

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    How did you determined that? Did you take the whole thing out ? There is nothing else there that could fail other than a few gears that transfer the load from starter to the flywheel. I'm curious!

    Here is how I would test it:

    Once you have the freewheel (#12 )in your hand when you put the sprag on it you shpuld be able to turn the freewheel by hand without any resistant but of you turn the sprag or spage attached to the stator magnet (#18) to the same direction , then it should makebsolid engagement with the freewheel.

    Try to force by stopping the freewheel with your other hand see if slips. Look for wear marks on the beans of sprag (a bit of wear normal to some degree) and no wear or scratches on the freewheel.

    [​IMG]
    #53
  14. SteveO

    SteveO scratched and bruised, but not out Supporter

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    I know this thread is over a year old, but in my research of the starter Sprag brought me here.


    In reading and looking through people's responses, this is just a full on horror-show.



    In the teardown of my bike I've noticed that my Sprag gear is brand new. It appears the previous owner replaced this part at least. I'll have to inspect the Ingition Rotor and the Freewheel to determine the condition of those items. Hopefully they are new as well.
    #54
  15. keener

    keener Speed changes you.

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    I'm now doing this on my girlfriend's BMW F650GS. I heard it making that nasty bang sound once or twice. Tonight I pulled it apart. This Austrian Rotax engine is very similar to LC8. The sprag system is nearly idendical.

    Anyway, I'm writing this here to say on the BMW world someone has figured out which oil seal shares the same spring used in their starter sprag.

    Replacing that spring early can save you from having to replacing the whole sprag.

    I looked this up for LC4 engines that has similar sprag I used in my write up here. I found this thread:
    http://advrider.com/index.php?threads/222515/

    On that thread someone claims SKF Seal # 19993 has the exact same spring we need. And if that works for LC4 it will work for LC8. Someone should try this.

    Cheers
    #55
    Bonnie & Clyde likes this.
  16. SteveO

    SteveO scratched and bruised, but not out Supporter

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    Very important info here. thanks for the info.
    I've ordered my 640 Sprag for my 950. I plan on measuring them to see the exact differences.
    #56
    outbacktm and keener like this.
  17. gefr

    gefr Life is a trip

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    O. C. In full deployment.:clap
    Cheers
    #57
  18. rossguzzi

    rossguzzi 990 Adv.

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    Any news on this ??

    Also, is it mainly the 950`s that suffer from bolts coming loose ? Mine starts just fine, no noises, just wondering if I should pull the cover and check ?

    Cheers.
    #58
  19. Unsquashable72

    Unsquashable72 n00b

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    #59
  20. Unsquashable72

    Unsquashable72 n00b

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    Hi I did my sprag at the weekend and had to fit the LC4 as complete be because the housing if the LC8 completely fell apart. I fitted the LC4 sprag with the circlip facing inwards to the engine. When trying to start it, it now just spins on the shaft, could someone let me know if I have put the sprag in the right or wrong way round? The mating surfaces are a little worn so not sure if this is the reason?
    #60