95-97 KTM LC4 Flywheel / Rotor warning

Discussion in 'Thumpers' started by Donkey Hotey, Jun 21, 2006.

  1. Donkey Hotey

    Donkey Hotey De Jo Momma

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    There was some tribal knowledge floating around regarding the failure of some 1996 KTM rotors. Basically, the rotor magnets would disbond from the flywheel and chew the stator to bits while circulating broken magnet pieces in your bearings (not good).

    The parts were silently upgraded somwhere back in 96-97 time frame. I never knew what the visual difference was to be able to identify the good one from the bad one.

    Thanks to help from Tom S who shared pictures of his destroyed rotor, we now know how to visually identify them. Mine had not self destructed (yet). This is what they look like:
    View attachment 76225

    It only takes removing your ignition sidecover and replacing one gasket to have a look-see. The difference is obvious when you see them. The old style has exposed magnets with glued joints. The new part has the magnets enclosed behind sheet metal. I don't think the part numbers ever changed. I ordered a new one for my 96 Duke and those are the parts side-by-side before I installed the new one.

    This was 'known' for 1996 LC4's but may apply to late 95's or early 97's. Be safe instead of sorry. Don't wait for it to destroy your engine.
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  2. Donkey Hotey

    Donkey Hotey De Jo Momma

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  3. creeper

    creeper Still alive...

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    Interesting that KTM would continue to use a segmented magnet rotor into the mid 90s when everyone else had gone to the one piece magnet in the late 80s.

    Just a little addition to your interesting and useful post... the segmented magnet rotors are very fragile. If you drop one, even tap one with a hammer, you can loosen the glue seal of one or more magnets. You can even break a magnet into pieces.

    For those that have this type rotor, any time you remove it, handle it carefully and always "thumb check" the magnets to make sure they are still well glued in place.

    Good post Greg :thumb
    C
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  4. Donkey Hotey

    Donkey Hotey De Jo Momma

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    So you wouldn't automatically replace one of those 'old' rotors? At least some of the engines I've heard of had never been apart and the magnets failed anyway. It was enough of a reason for me to buy the part preemptively ($275 IIRC). What say you oh mighty Creeper?
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  5. ChrisC

    ChrisC Amal sex?

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    I'm wondering what the clean point is for the change-over from the segmented rotor to the single piece type ('98 - '99 - ?)
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  6. Donkey Hotey

    Donkey Hotey De Jo Momma

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    I should add that getting the starter clutch hub off the back of the old flywheel was a PITA! They used some kind of gray thread locker that put red loctite to shame.

    It took a propane torch on each bolt (6 of them) to get them loose. Once out, I had to chase the threads multiple times (with oil) to cut all the threadlocker out. Even then, it was so tight I feared breaking the tap (6mm). It was some mean stuff. I used contact cleaner then red loctite for reassembly.
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  7. creeper

    creeper Still alive...

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    If one can afford it, and/or it's available, then yes I would replace it as a kind of preemptive strike... but for those where that's not possible or practical, then a thumb check would at least provide some peace of mind.
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  8. Donkey Hotey

    Donkey Hotey De Jo Momma

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    I can't swear to it but an educated guess would be that it only applies to electric start LC4's. 1996 was the first e-start models (Adventure and Duke). That's also the year the problem cropped up.

    Yours doesn't appear to have the same construction. If it were mine I'd leave it alone. This is exactly why I posted the pictures. I didn't know what the bad one looked like either.
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  9. Beez

    Beez Given to fly

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    I had one of the segmented rotors on my '97 620 RXC. :cry Failed and damaged the stator too, however the bike still worked. It did not look as bad as Tom's. I attempted to fix it myself but when I got to those 6mm allen head bolts I cried uncle and gave it to the professionals. It now has the solid rotor. :D
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  10. Donkey Hotey

    Donkey Hotey De Jo Momma

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    So that was an electric start model? It sounds like 'yes' since you mentioned the 6mm bolts.
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  11. Beez

    Beez Given to fly

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    Yes. e-start.
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  12. Donkey Hotey

    Donkey Hotey De Jo Momma

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    I finally tore down my 97 620 Adventure's engine last night. I'm not the first owner so I can't swear that the rotor wasn't changed but it has the newer style rotor.

    So based on Beez having the old style and my 97 having the new style, it's fair to say that 1997 was the crossover year (might be yes, might be no--safest to look). Any e-start from 96 is a must look. Consider this to be the KTM's 'doohickey.' At least KTM fixed it though :lol3
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  13. Nico

    Nico The Sexiest of Silverbacks.

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    Thought I'd wake this thread from the coma it's been in for 2+ years.

    Why might you ask? Because my segmented magnets gave up the ghost this weekend. 1500 miles after I had inspected the things visually/thumb pressure style. Dammit. :baldy

    Fundage was in limited supply and I honestly have seen very few reports of these things failing, so I felt safe in gambling these were good to go. I lost.

    My bike is a 1997 RXC 620, e-start.

    Situational background:

    I've been riding to and from work up until Tuesday of last week, when I swapped my road oriented tires to DOT knobbies for the trip up north (woohoo!). Never any indication of trouble until Friday afternoon, when I tried to fire her up for a quick ride around the property. She just said click click click. WTF? She fired first kick, so I though nothing of it. (Battery must be on the way out, right? Sure.)

    Well, I got about 15 miles or so into this little ride and realized I'd neglected to top off my tank. Of course, this was when she sputtered and quit. I switched to reserve and tried to pop start her from about a 25 roll. Instead of roaring back to life, the rear locked in the sugar sand, bringing me to a stop. Put my foot down, into a hole of course, and gently laid her down on her port side. Picked her up and saw a nice oily puddle andmy timing sight glass laying in the sand. WTF? Dismount, clean the glass best I can and try to push it back into place. Except, I see two frayed wires in the timing window. Oh shit, this thread pops into my mind. :(:

    Step back and notice a couple pieces of "glass" in the oily sand. Broken bits of magnet. Oh shit. This sucks royally. Stuff the sight window back in place, push the bike to the side of the trail, leaving the key in the ignition just in case someone wants to relieve me of my new headache. (full coverage is cheap) Walk the 3 miles back to camp, grab trailer and bring Elsie back. Cursing all the way. :becca

    Where I stand now is wondering how far into the motor the shards of magnet made there way. Hopefully, they are all local to the magnets and haven't been circulated. If someone with knowledge of whether or not there is a oil return passage in the stator/flywheel/starter motor housing, please speak up. My gut feeling is there are probably little abrasive magnets in all my bearings, but I am a bit of a pessimist when the shit hits the fan, FWIW. Hopefully, that's not the case. If I have to go beyond the 4-hunny in parts I am looking at right now, she may be on the parting block. I really don't want to do that, but money's tight around Detroit these days.

    I have had little luck finding the oil circuit schematic that has been posted here numerous times. If someone can point me to that, I would be grateful.

    I need to track down a flywheel puller tool. If somone has one I could borrow, I'd be grateful. Even willing to pay a rental fee. That, or maybe I'll go the way that has been suggested in Losiu's thread for the starter re-build about using a HF cheapo. We shall see.

    Couple pic's I took tonight...

    Shards of magnet picked from the sand. (notice the grains still attached)
    [​IMG]

    Oil pan plug magnet... (not too furry, I hope)
    [​IMG]

    Busted magnets and ruined stator...

    [​IMG]

    And, introducing Minnie, my '69 MTD TrailFlight mini bike. I figured I could ride her all weekend, you know, make the most of it. Till her carby gave up the ghost and started pouring fuel from the overflow hole every time the petcock was opened. One of those weekends, I guess. :baldy
    [​IMG]

    Sorry for the big assed pics.

    Fair warning for anyone with early e-start LC4's. Swap the flywheel if you have the segments. This sucks ass, I can attest. Bitch of it all was this is the best she's run since I got her and we were tearing up the sugar sand like nobody's business. Ohhhh, the memories.
    #13
  14. jfn68

    jfn68 Banned

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    The mid90-late 90 lc4s are also known to give cdi/coil/stator problems,both my 95/98 both had issues.
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  15. Donkey Hotey

    Donkey Hotey De Jo Momma

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    Wow, I'm really sorry to hear about your blown rotor. When I saw activity here, I was hoping it was due to the Husky TE610 thread that I started:
    http://www.advrider.com/forums/showthread.php?t=374357

    A picture was posted of a 610 in pieces and it sure looks like they have the same, segmented rotor as the LC4. So far, nobody has responded. Maybe they didn't have the problems?

    I can't say for sure what I'd do in your situation. Obviously, you need a new rotor and maybe the stator. Since it's a big magnet, I'd look around elsewhere for magnet particles. There's no stronger magnet in that engine so if all the debris is ferrous, there's a fair chance that it's all stuck to the flywheel or stator area.

    A tear-down would be no fun. Since it blew while it was running, what's the worst you could do now? If the bearings are contaminated, they'll let you know after a few hours of running. If not, mabye you got away with it? It's worth a try.
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  16. meat popsicle

    meat popsicle Ignostic

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    :cry

    dagnabit! Well, I can help with this bit:

    [​IMG]

    and no, I'm not sorry'bout the big ass pic. thanks Creep :wave
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  17. Nico

    Nico The Sexiest of Silverbacks.

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    Thanks guys. I thought Meatpop might be the one to have the schematic I sought.

    Gotta get hold of a flywheel puller to inspect a little further into the motor. I may bring a boroscope home from the office today to have a looksee at the crank and inside the oil pan. I saw nothing worrisome in the oil I drained last night, but I can't say that means anything, as the contaminants are magnetized and would likely be clinging to the crank/rod/cams...

    I am leaning toward Donkey's POV in that if the motor is contaminated, it's beyond just cleaning it out with a flush or two. If I cannot determine either way, I'll just replace the rotor/stator and ride the thing, hoping all the fragments were contained. I should know in short order if there's an issue.

    Hoping Beez will see this and offer up the state of his mill after going through this. Sounded like he swapped the bad parts and rode it. It'd be nice to here he's put thousands of miles on it since then.

    jfn68, I've read about the CDI/coil issues too, but these definately fall under the "If it ain't broke, don't fix it" category because if they go, it is a mere inconvenience. Not potentially catastrophic like this mess.

    Thanks again fellas, now I gotta get back to work. :marc
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  18. dentvet

    dentvet Long timer

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    Sorry about the magnet grenade. Is there anything one can see through the sight glass on these that might warn of an impending problem? I just thought it might be an easy thing to include in a pre-flight inspection routine. If you decide to part it out, i'll take a chance on your powerplant, dave
    #18
  19. Nico

    Nico The Sexiest of Silverbacks.

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    I don't think you'll see any indication through the sight glass. Maybe you would, but it would likely be too late at that point.

    Popping off the timing cover and inspecting the magnets is prolly the only way to go. They are glued in place, so a close look at the mating areas MIGHT give indication of impending doom. Again, I had a look at these this past Spring, and I felt confident there was no problem. It's a gamble if these are in there. Heat cycling and adhesive degradation are, IMHO, the two biggest factors in the failure of these magnets, aside from the piss poor design.

    I'll keep you in mind if it gets parted. Gotta do the math to see if it's worth keeping. Smile factor weighs heavily, though. Prior to this fiasco, this has been one of my favorite bikes. Big shit-eatin' grin every time I got off the pavement. :ricky
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  20. todd83-900t

    todd83-900t Been here awhile

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    Nico,

    I'm sorry to read about your troubles!

    If you do decide to "gamble" I'd suggest that you have your oil analyzed after you flush the engine several times and take it for a short ride.

    -t
    ( please ping me if you decide to part the bike out)
    #20