KTM 690 SM LC4 engine rebuild

Discussion in 'Thumpers' started by mbrick, Jul 8, 2013.

  1. mbrick

    mbrick Been here awhile

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    Hey Advrider,

    I am chronicling the rebuild of my 2007 690 SM LC4 engine here. Bike has 12k miles.

    It had a bad noise in the bottom that I suspected was the balancer bearing or maybe a crank bearing. Here is a video of the sound. It would go away after about 2-3 minutes idling, which is the strange part... you'll hear it stop near the end of the video then it sounds normal.

    The cam chain was tight with a manual CCT (maybe even a little tight for my judgement), so I don't think that was the source.

    Now on to the fun work!

    Started by draining the oil and coolant. Oil screen on the tranny side shown, other was clean.
    [​IMG]
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    Cheated and used the rear brake to loosen the clutch nut since I don't have the tool to hold the basket.
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    Next removed the motor, fairly straightforward, didn't get many pics. Toughest part was the frame pinching onto the back of the engine through the swing arm pivot.
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    Finally split the case and removed the balancer.
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    I am concerned about the balancer shaft grooves from the 2x seals and possibility it already allowed a little water to seep past to the bearing. Should I replace it?
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    Closeup of the suspect bearing. It feels gritty/rough, especially compared to the other side so I am fairly certain this was the problem.
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    Note broken oil ring. It could have broke when it opened up after coming past the edge of the cylinder but I don't think that is likely.
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    Right case cleaned up.
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    Left case cleaned up.
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    A little concerned about wear on the small oil pump:
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    Big pump looks good:
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    Transmission gears look good, no pitting or missing teeth. Shift dogs have very minor wear
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    Bore has 1 section with a few lines but otherwise no signs of wear. I suppose nikasil is pretty hard after all :eek1
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    Cleaned piston, very little wear.
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    Photos of broken oil ring. Was going to replace rings anyway.
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    Exhaust roller needs to be replaced (as I suspected from reading many posts). Not much movement in the bearing but the galling is a no-go.
    [​IMG]

    Also took apart the starter to clean/grease. Stopped here because I am concerned about holding the 4x (four!) brushes back when re-inserting the stator. Really would like to re-grease the bushing in the back though.
    [​IMG]

    Valves and head look good, no oil on any stems. I will remove the valves to change the valve stem seals. Intake clearances in spec, will check exhaust with new rocker. Should I look for anything else?
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    Cam looks good.
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    Had the non-iridum equivalent, electrode is still sharp, I will use a new factory iridium plug though.
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    Very little play in the big end of the rod, at least as I would grade it quantitatively. I had considered having a new rod kit installed but probably won't.
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    [​IMG]

    I have blown through the oil passages with compressed air and nothing seemed restricted.

    I'll compile a list of specific tools used once I finish.

    I'd like to hear your thoughts!
    #1
  2. mbrick

    mbrick Been here awhile

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    Continued...

    Next steps:
    -Will have a friend help me measure the bore and piston this week to compare against specs and check clearance to make sure I don't need a piston
    -Decide on balancer replacement or not
    -Decide to further take apart starter or not
    -Finish cleaning the few remaining parts
    -Order 2 balancer bearings, rings, exh rocker, gasket kit
    #2
  3. Motomochila

    Motomochila Mad Scientist

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    You are moving in the right direction but I'd go ahead and replace the big end with a rod kit. The labor to do everything far outweighs the money to replace now. Tearing apart again next year after only a 1,000 miles is a PITA. Also 12,000? I suspect you are hard on the throttle and wring it out to the top before shifting. Ring shouldn't break so early. She's got more than enough power if you short shift and your motor will live much longer. Add a few teeth to the rear sprocket and you'll get all the excitement you need since you rarely ever need the top end based on stock gearing.

    Just my opinion after doing the same with mine, only at 9,000.
    #3
  4. mbrick

    mbrick Been here awhile

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    What rod kit did you go with and who'd you have do the work? ProX is cheaper but I prefer stock parts.

    I was planning on going from 16/40 to either 15/40 or 16/42 since the sprockets do need replacing.
    #4
  5. mbrick

    mbrick Been here awhile

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    Just wanted to provide an update after having a machinist help measure the parts:

    Piston I: 4.0146"
    Bore I x / y: 4.0157" / 4.0156"
    Piston to bore clearance: 0.0011" or 0.0279mm.
    Crank runout: 0.002" main gear side and 0.003" flywheel side. We did give it a squeeze to see if it would improve but it was pretty happy there. Would have liked to see less runout.

    So piston and bore are on the tight edge of the spec, and clearance is just under the tight side. Impressive for the mileage. He said the big end rod bearing and wrist pin both felt like new so I won't replace them.

    Will go with a new ring set and a new balancer due to the heavy grooves. Surprised the shaft was not heat treated.
    #5
  6. Gleado

    Gleado Adventurer

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    You might want to heat treat or surface harden the balancer where the seals ride or it will just happen again. See if you can upgrade the bearing also with a higher grade bearing. Bearing supply houses can be your friend. I ride a DR650, ok flame me, but I'm 51 and don't ride as fast as I used to so it works for me. I've thought about getting a KTM but still in the research mode.
    #6
  7. mbrick

    mbrick Been here awhile

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    Good point about heat treat or carburizing, I will ask around.

    I suspect the bearing failed from water ingress past the seals?? Just a theory though. It's a NTN from Japan, what would you consider higher quality?

    Depending on what style riding you do, you should look at one of the 690 models. I know the DR will last longer than 12k miles before any major work, but I think KTM's are still really high quality. Otherwise I wouldn't continue buying them!
    #7
  8. Gleado

    Gleado Adventurer

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    There's lots of different brands like NSK, FAG, etc. I'm no expert but I do have a good bearing house in Albuquerque. I rely on those guys to help with the upgraded bearings. If the original spec'd bearing has held up I will usually replace with same grade. I'd go by failure rates based on what you hear on the forums. Bearing upgrades are not big hitters cost-wise. You can even go ceramic or plastic cage if you don't like the metal cage bearings cause it fragged your trans upon failure. Just be sure to let them know what application your dealing with as sometimes temperature and other factors must be known to properly select the new animal. 11k miles is bogus though that's why I suggested upgrading. Sometimes you can get bad bearings like anything else, but I sure wouldn't go with what you had. As far as my question on KTM's, I'm just trying to get a feel for what I'm in for reliability wise. I ride with guys on occasion running KTM's I'll start asking around. What I like about them is the lightweight and apparently they handle really well too. Good luck with your rebuild!
    #8
  9. Orangeshirtdude

    Orangeshirtdude Fight the Power Commander

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    How are things looking on this? I have my LC4 from my 08 690 SMC that I have to tear into. It has just a hair under 30K miles and started making a horrible noise that was different from yours. Mine has shed metal into the oil too--it's definitely a bearing somewhere.

    The first thing I checked were the rocker arm bearings as those are known to fail. Mine were fine, but I discovered an odd thing. My valve clearances opened up a ton, as in I measured as much as 0.6 mm on one intake valve. I traded messages with a guy in Europe who said his shat a cam bearing. The hypothesis is that the 690 LC4 engine does not pump adequate oil to the top end during long wheelies. Anyway, without coming right out and saying it, I'm hoping mine is the same issue.

    On the other hand, it could be something worse, considering the mileage and that I absolutely flogged this bike. Even though I was very meticulous with maintenance and running good quality oil, 30K miles is a lot for a big bore single.

    Ok, now for the most important question: For someone who has never split a case before, how miserable a project is this 690 LC4 rebuild? I do have a machinist/mc mechanic who can advise and help out, but he hasn't opened up one of these particular engines either. Can you offer a "difficulty rating" on this?
    #9
  10. gen

    gen Been here awhile

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    You must have flogged it :D


    Mickwheeler put 100,000 miles on an '09 690 Enduro R
    with only a replacement of the intake/exhaust rocker arms/camshaft at 31K miles. That's the highest mileage 690 that I think anyone has seen on ADV.
    #10
  11. wvridgerider

    wvridgerider Been here awhile

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    After this would you buy another 690?
    #11
  12. Albie

    Albie Kool Aid poisoner

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    Heh, I flogged the shit out of mine. The top end was worn the hell out at 27K miles. :lol3
    #12
  13. Orangeshirtdude

    Orangeshirtdude Fight the Power Commander

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    That's amazing, 100K? Wow. Getting 100K on any bike is an accomplishment.

    I rode mine hard and will know fairly soon how bad off the engine is.
    #13
  14. davesupreme

    davesupreme grand poobah

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    i know on the RFS motors, the crankcase vent is just above that bearing, and if you get water in the line, it's supposed to kill that bearing....
    #14
  15. MrHix

    MrHix Been here awhile

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    Thanks for this thread mbrick, I hope it doesn't become useful to me for another 16K miles or so. :D

    Cheers,

    MrHix
    #15
  16. mbrick

    mbrick Been here awhile

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    I finished rebuilding it and have been meaning to add more pics and an update for the reassembly. All is good, have ridden about 600mi so far without issue. Well, the running light on my taillight just stopped working but that's a separate problem.

    It was a rather straightforward rebuild. KTM builds nice engines. As long as you have worked on engines before (maybe a top end rebuild) and have the service manual on hand I think you can do it. One of the most challenging parts is actually splitting the cases, you have to resist using anything to pry on the sealing surfaces or it will leak after reassembly. Actually dropping the engine from between the frame/swingarm was also tough, it is a snug fit. Just be patient as you go.

    I think you should try to narrow down if the problem is in the top or bottom and let us know what you find.

    I'll get a writeup done in the next few days for reassembly/install :D
    #16
  17. Orangeshirtdude

    Orangeshirtdude Fight the Power Commander

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    Great, thanks for the info. I have been mentally preparing for the task of dropping the engine out of the frame and swingarm. Once out, I'll start with top end and see if I get lucky and just need to deal with a bad cam bearing.

    I'll document my endeavor and post it too. I'm sure there will be ways the two threads will complement each other. :freaky

    I look forward to seeing your reassembly.
    #17