Should I crack open my LC4?

Discussion in 'Thumpers' started by Umarth, Jan 12, 2013.

  1. Umarth

    Umarth Been here awhile

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    It all started when I went to do a routine oil change on my 640 adv with 40,000 km.
    Noticed the oil was like milk chocolate.
    No big deal: had all the parts for water pump rebuild in hand.

    So I fixed the water pump. In doing so, looked at the piston and figured,bah while I'm here might as well clean it too and check what the cylinder walls look like and check the ring gaps. So proceeded and remove the cylinder.

    Now I'm thinking, since I have 3 and 1/2 months left before the big ass trip (100,000 km estimated), maybee I should crack open the case and check out the wear on the trans an replace some bearing in there while I'm at it.

    My question is, any reason I should refrain from doing it? I'm learning all this shit as I go along, beeing a noob mechanic after all. But I'm not affraid to get my hands dirty and, more importantly, the more I know this bikes internals the better prepared I'll be when it craps out in the middle of patagonia or the sahara.

    And If I do go and crack the case, what should I be looking for exactly and what parts would be good candidates for preemptive replacement? Main bearing? all the bearings? the gears? I dont want to spend uselessly on this (takes away from travel money - beer) but, well, you know... :freaky
    #1
  2. gunnerbuck

    gunnerbuck Island Hopper

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    I wouldn't bother splitting the cases unless you can feel or see a real reason to do so... The most I would do is take the clutch side cover off, remove the clutch and then inspect the bearings in that side of the case for play... You can inspect the con rod big end bearing while your cylinder is removed, look for excessive side to side movement as well as up and down slop.. You can check the crank end bearings for side play by grasping the gear end of it and see if it moves, there should be little felt movement... A dial guage can be set on the end of the crankshaft to check runout... You can inspect the mainshaft needles by removing the clutch slave and wiggling the end of shaft looking for slop in the needles... The same with the countershaft, remove the sprocket and check for wiggle and excessive lateral play... All this can be easily done with the engine in the frame... Remember to replace the clutch nut retaining washer and before you re-install the clutch side cover you should replace the crank end seal that rests in the cover close to the oil window...

    Just a note: The 640 engine is put together almost exclusivly with roller bearings on all shafts rather than ball bearings... These rollers if properly lubed have a very long service life... With only 40,000 km on your bike there will likely be very little difference between the bearings in your engine now and a new set if you were to replace them...

    What does kill a roller or needle bearing quick is if a chunk of slag gets pinched between the rollers and the races... That is where good oil and regular oil changes come in to play by getting rid of the particulate before you get a buildup within the engine...
    #2
  3. fastdadio

    fastdadio Still gettin faster

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    With that mileage/KM's. I would recommend also replacing intake side cam follower bearings, cam bearings, and the piston rings. While the cam bearing failures are duly noted in the sticky, there were a number of top end demos at around this mileage that were caused by piston ring failure. Ring are cheap....your already in there.....just sayin... :deal
    #3
  4. Aussie Steve

    Aussie Steve Long timer

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    Personally with a 100,000km trip planned I would split it and have a look. Probably more for learning how to do everything on your bike in the comfort of your own home before you leave.

    I have split mine at 70k as I have a cracked head and output shaft spline isnt so good, there are a couple of bearings which I'm not thrilled with the look of already.

    I reckon as suggested you rebuild water pump, replace cam followers, change seal in the case for conrod bearing and also change the thermostat. Anything else you change might be wise to package well and leave with someone who can freight to you if needed during your trip. All these suggestion are probably overservicing but are cheap peace of mind.

    Dont forget steering and suspension bearings and suspension revalve/rebuild.
    #4
  5. bmwktmbill

    bmwktmbill Traveler

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    I wouldn't slit the cases but I would do everything else. If you get real nosey pull the oil pumps apart just to look and remove the oil pressure relief plunger to check for scoring. I'd put some effort into collecting spares to carry and the tools you will need to repeat the processes you are involved in.

    Service the carb, grease every electrical connection checking for sharp areas on the frame that will abraid the wiring and reinforce/protect those areas.

    I'd find some HID lamps and install them if you want a project and a Scotts Steering stabilizer. Rebuild the suspension, change oil and seals front and rear.
    Panniers?

    Plan your trip so you are in Europe or the USA or Chile or go see Aussie Steve around 120K KM or Gunner or me...what could be more fun.

    IMHO.
    bill
    #5
  6. gunnerbuck

    gunnerbuck Island Hopper

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    For sure if you get up to northern Vancouver Island, stop by and we'll change the oil, adjust the valves and do a little tour...
    #6
  7. Aussie Steve

    Aussie Steve Long timer

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    And you are also welcome in Australia. Am about halfway up the east coast, let me know if you are nearby.
    #7
  8. Umarth

    Umarth Been here awhile

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    Wow! Really is starting to feel like a big familly on here!!
    Gunner, I'm starting off from Quebec mid may. Contemplating doing all or part of the Trans canadian trail (well, from QC to BC), then up to alaska and then back down all the way to terra del fuego. I dont have any time table other than I need to be in costa rica by mid september.
    So yah, I'll definitely take you up on that offer! :):freaky
    Hell, if you haven't sold your seat by then I might even take it! :lol3

    And steve, Australia is still uncertain at this time as it would be the last leg of the trip,and the further down the road, the more the trip gets fuzzy. But if I do I sure as hell wouldnot mind sharing a beer while changing the oil...
    #8
  9. Umarth

    Umarth Been here awhile

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    and while I have the attention of you guies who know about the 640 quite a bit.
    I was told by someone that seemed to know his shit, that to minimize the chances of the 640 detonating down south on cheap gas, that I should replace the exhaust for something less restrictive.

    What are your thoughts on that? There is an akropivik for sale right now in the flee market and I could grab it. But I not sure I really need it plus it add's maintenance (every 20,000km need to repack it from what I'm reading). PLus the fact that I'd be shaving off some weight high up sure does sweeten the deal...
    #9
  10. Luke

    Luke GPoET&P

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    The akro is way too loud for touring unless you're already deaf. Even with earplugs in it sounds loud.

    I have a more-open-than-stock exhaust and it detonates on cheap gas- but a little less than my friend's 640 with the akro on it. The differences were the carb (his stock, mine FCR) and the piston (his stock mine woessner).

    I've had problems with both canadian indian reservation gas (labled as low octane) and Mexican 'high octane' from a Pemex station. The ignition timing can be modified by filing the holes on the sensor mount, I'll do that before running odd gas again.

    What year is your bike? 2003+ had a selectable ignition curve for cheap gas. That supposedly works great, but also hurts power and fuel economy.


    Since you have the top end off, I'd suggest replacing the piston with a Wossner. It's lighter for less vibration and has thicker piston rings which should be stronger.
    #10
  11. gunnerbuck

    gunnerbuck Island Hopper

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    You could also install a thicker base gasket to slightly lower the compression, this would smooth things out a bit and make the engine less high strung.... I picked up four base gaskets that are intended for the early model LC 4 and are 0.7 thick compared to the 0.5 of the later bikes...

    With the stock exhaust just pull the disk pack off the back of the muffler and then drill a bunch of small holes in the end plate {swiss cheese effect} around the core pipe... These holes will create a shortcut past the restriction and let some of the exhaust through without much increase in noise... When you reassemble add another 3 or 4 disks to the stack...
    #11
  12. bmwktmbill

    bmwktmbill Traveler

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    Umarth,
    The Central American dist. Is in Guate City in Guatemala, not sure for Sud Amerika but maybe Chile.

    A rebuild outside the first world would be cheaper for labor, parts maybe more?.

    My basement is full of tools, you are welcome any time.
    I don't lock the doors, I don't have to be here for you to use the house.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]


    bill
    #12
  13. Umarth

    Umarth Been here awhile

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    Euh... failing to decifer this part! what you refering to here?

    Wow! that's generous of you!!
    #13
  14. bmwktmbill

    bmwktmbill Traveler

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    Umarth,
    The KTM distributor for C. America is in Guatemala City if you need parts.
    I had good luck with them when I needed a piston.

    In S. America, I am not sure where the distributors are, Chile maybe or Columbia, I never rode a KTM south of Panama so I never checked.
    bill
    #14
  15. Umarth

    Umarth Been here awhile

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    Here are some pics of my cylinder:
    [​IMG]

    [​IMG]

    it's a bit hard to convey the grooves I'm seeing so I took a quick video of on of the groves, and to fully see you need to play it in 720p min, 1080 is even better:
    <IFRAME height=630 src="http://www.youtube.com/embed/aCgwevtfW9c" frameBorder=0 width=1120 allowfullscreen></IFRAME>

    didn't take any pictures, but the piston has similar scratches on it's skirts(?).
    If you just glide your finger over the surface you hardly feel anything, but pass your nail 90deg to the scratches, you feel them, but it's still slight.

    so, I'm wondering two things:

    1. what is the root cause of these scratches? It's pretty obvious that particles got between the cylinder and the piston, but is it a sign that something in the engine is disintegrating? Howcome particles big enought to bridge the gap between the cylinder and the piston skirts got there in the first place?

    2. does the cylinder need to be re-plated? concidering the long trip I'm about the take of course...

    3. unrelated question, I've got one ofthe lc4's that vibrates a lot and I wouldn't mind minimizing that vibration. Since the piston is already out, would switching to a lighter piston garantee to help (even just a tiny bit would be fine) reduce the vibrations? Or can it go eather way? And if I do go with a lighter piston, what's their durability relative to the OEM ones?

    thanks.
    #15
  16. Umarth

    Umarth Been here awhile

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    Oh I like that idea of simply reducing the compression ratio! Brilliant!
    The thicker ones, where from what year model?

    as for the exhaust mods, I'm pretty sure I don't follow your instructions but that's simply because I've never taken one apart, so I'm not visualizing the steps. Google time! :)

    thanks for the info!
    #16
  17. achile

    achile Been here awhile

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    My friend, it seems to mee that you have an all-mighty itch to crack it open and see how it ticks. So...you are seeking the approuval of your peers...

    DO IT! Change the worn parts and you'll sleep better in Patagonia. :D:1drink
    #17
  18. mountaincadre

    mountaincadre Been here awhile

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    Well if your doing Europe you might as well pop in or a cup ae cha(tea), i'm in Scotland, the weathers shite but the roads are braw.Hey gunner i've taken your advice and dicided not to fit the 660 rallye cam to mine as it's already nippy enough and like you said "the more you tune it the greater the chance of self destruction and the more i'll have to service it", i'm half way through the rebuild of mine, i;ll post some picks when it's finished.
    #18
  19. achile

    achile Been here awhile

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    I did my top end last november. I had a difficult choice to make. Go stock or put in hotcams and big bore. I went with the stockye. It all depends on what you want to do with it and how it reflects on your finances. Are 4-8 hp worth spending a few houndred bucks and increasing the risk of a fatal engine faliure?(maybe at high speed, with you on it?) Service costs? I'd rather have it in perfect shape and stock. (I'm talking about the BRP I own since 2008.)
    #19
  20. mountaincadre

    mountaincadre Been here awhile

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    Aye Achile that's the conclusion i've come to, mine has 54 at the rear wheel and that feels more than enough.
    #20