640 LC4 Adventure 'bleeding' oil on head gasket?

Discussion in 'Thumpers' started by QMan, May 29, 2006.

  1. QMan

    QMan prof. dirt mover

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    Hi,

    Anyone has an idea on what might be causing this?
    I am loosing a tiny bit of iol near the exhaust headers on the head gasket. First I had some dirty goo on the valve covers, got those gaskets replaced by the dealer et voila all good, until I took the bike for a ride on highway, with app. 85 mph speed and when I pulled over I noticed some tiny splatters of oil apparently leaking from the head gasket.

    Now, my concern... is this just a gasket problem, or is this something worse? Someone I knew said I had underpressure which indicates wear on the engine... what needs to be replaced in order to fix it? The engine has 18800 km on it, never had a problem :(

    Help please from all you guru's :D

    Q
    #1
  2. Bush Basher

    Bush Basher Adventurer

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    #2
  3. creeper

    creeper Still alive...

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    I don't think it's the head gasket either... and it may not be the rocker cover gasket, but instead the upper flange bolt of the left exhaust header.

    That particular bolt hole is drilled thru all the way into the inner cam/rocker cavity and opens out directly below the left front head bolt.
    If the threads are worn or the bolt is not torqued correctly, oil from the rocker cavity will dribble out past the threads and down the front of the engine on the left and around the left header.

    The common fix is to remove the bolt, degrease the head and in particular the bolt hole, then reassemble with a generous helping of high temperature sealant on the bolt.
    This should be allowed to cure for at least 48 hours, and preferably 72.

    C
    #3
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  4. QMan

    QMan prof. dirt mover

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    Creeper could be right and sorry my mistake it indeed is the rocker cover not head gasket... if it is leaking.

    I'll try and see if the bolt is correctly torqued somewhere this week if I find time. In the meanwhile I cleaned all gooy and it looks like an engine again :)

    Bush what milage you have on yours?

    From the 18000 I have about 8000 serious offroad km's.

    Cheers and thanks!

    Dom
    #4
  5. Rideguy

    Rideguy Kamikazi on one wheel

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    Creeper...

    I also fall into this catagory, and since my rebuild a couple years ago... I had to replace the base gasket to a metal one because they sent me a paper one for the re build...

    I have been leaking oil by the left exhaust port like mentioned in the above posts and in hindsight has been leaking since the rebuild. I have an 03 LC4e but got the 04 top end and thought maybe the header pipe doesn't fit too well.... Could there be a difference in bolts between 03 and 04?

    I've had the tank off a few times and could not really locate the leak, but this sounds like a great lead....

    What is the proper torqe setting for this bolt?

    T.I.A.
    #5
  6. Bush Basher

    Bush Basher Adventurer

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    My bike has done 11500 km on the clock.
    It's a X demo and I ride mainly off road, gravel roads and riverbeds with short trips on the road to get to the riding area's we use.
    That is a part from this weekend as I'm doing my first tour on it.
    #6
  7. dagwood

    dagwood Banned

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    wow never heard that. mines been drizzling for months and it drips right on the left headpipe when I slow from higher speeds and sends up a puff a smoke. always thought it was the valve cover leaking as it's a bitch to see anything up there. even with the tank off.
    naw, it's gotta be the valve cover. when "I Get A Chance" :baldy I intend to go through it top to bottom and do the bearing at the same time. sucks being the daily driver. never gets a chance for it to sit long enough to pull it appart...
    #7
  8. creeper

    creeper Still alive...

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    The deal is, most LC4 rocker cover leaks occur above the left exhaust flange, and a bit towards the water pump.
    I've had theories about this, one being the lack of fasteners in that location combined with the heat generated in the exhaust port area combine to produce some warpage in the cover.
    All the head/cover sets I've had in the shop with warpage have had it in that location... nearly all of them.

    Then there's the header flange bolt hole... the only one that goes thru and opens to the interior of the head.

    [​IMG]

    [​IMG]

    If the threads are worn and/or if the fastener is loose, oil that collects in the hole will run down the threads and out.

    As the torque value on this flange bolt is only 10Nm (7ft.lbs), it's not like you can go in and tighten the crap out of it and the leak will stop.
    There are only a few "fixes" that come to mind with the head in place and no rocker cover disassembly involved... a high temp liquid thread locker or high temp silicone sealant.
    You can't get too carried away with either of these unless you want the excess sealant to be pushed into your engine... and for either to work, you need to completely degrease the bolt and threaded hole.

    Short of welding and machining, or an application of epoxy from the inside, there is no really good, permenent fix that comes to mind.

    One "Pet Idea" I've had to fix this in place is to remove the exhaust flange, and using a hand held drill with a counter boring bit, spot face the material around the bolt hole sufficent to insert an O-ring to a depth of about 70%-75% of the O-ring's thickness.
    The 25%-30% O-ring crush might be enough to "seal" the area around the bolt hole.
    It would have to be a high-temp O-ring.

    Without a through clean-up and inspection, what appears to be a rocker cover leak could be a flange bolt hole leak... and visa versa.

    C
    #8
  9. tonys

    tonys Adventurer

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    Think I've found a good cure for this one, didn't like the idea of just sealing the exhaust flange bolt, didn't like the idea of puddling glue into the rocker cover either, in case it came loose over time and blocked an oilway. So I took the exhaust flange off, took the rocker box off, cleaned up the threaded hole with carb cleaner. Got a 6mm long, M6 allen head grub screw, coated it in thread sealer, screwed it into the hole from the outside, right in till it locked against the head bolt. Then the original flange retaining bolt can thread right in as normal, with the grub screw acting as a plug. It can't get loose and into the rocker box cos the head bolt is in the way. It's worth putting an overlength bolt through the hole first to clean up the inner portion of the thread that is normally not used by the flange bolt, that way, the grub screw goes right in up to the head bolt. Left it all for 48 hours for the various sealants to cure, just got back from a quick ride and all oiltight.:D
    Thanks to brucee for the idea of using the grub screw!
    #9
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  10. creeper

    creeper Still alive...

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    An excellent idea! :clap

    Thank Brucee for all those that have had to deal with a leak in this area... he's a good man for thinking outside the box, and you're a good man for giving proper credit.

    Should I ever develop a leak (If it ain't broke, don't fix it) I will have a 6X6mm allen set screw at the ready. :thumb

    C
    #10
  11. Kopromayor

    Kopromayor kopromayor

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    More details please would be helpfull.:huh
    Any fotos?
    Thank you in advance.
    #11
  12. tonys

    tonys Adventurer

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    Er, well, meant to take photos, but got carried away and forgot! It's pretty straightforward though, Creepers photo of a partly bared head in his 'sealing rocker box' thread shows where the threadded hole breaks through into the rocker box, the head bolt 'lands' on the machined surface where the bit of red plastic is poked through, just make sure the plug grub screw comes through till it can be seen contacting the head bolt.
    #12
  13. creeper

    creeper Still alive...

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    What tonys is saying is to get a grub screw (Allen set screw) 6mm X 6-8mm in length, coat it in your favorite high-temp spooge, run it into the top left bolt hole until it bottoms out (lightly) against the head bolt washer (which by the way, you can't see unless you have your top cover off... see photos in post #8).
    Then... let that kick for a bit, say at least 24 hours, and reinstall your exhaust flange bolt.

    Step by step version:

    1. Remove upper left (right facing the head) exhaust flange bolt.

    1.A. Verify that you can get both the grub screw and the exhaust flange bolt into the hole sufficient to apply a load to the flange.

    1.B. If necessary, remove the entire flange so that you may run a "overlength bolt", or if you have one, a bottoming tap into the hole sufficient to get both the grub screw and the original flange screw fully into the hole.

    2. Clean the living daylights out of the hole... repeat until well clean. Best to do this with product that is fast evaporating as you do not want a puddle of it inside your head.

    2.A. The absolute best time to do this is when you are also doing a rocker cover reseal. That way, you can see what's going on at the back side of the exhaust flange hole, and blow out any spooge, chips and schmutz from the inside.

    3. Apply high-temp sealant of choice to grub screw, thread fully into hole until it bottoms... again don't over do it as you could apply a side load to the head bolt, causing mucho problemos later down the line. Allow sealant to dry.

    4. Reasemble... go forth and leak no more.

    C
    #13
  14. tonys

    tonys Adventurer

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    What's the issue with applying a side load to the head bolt? I must admit, I've done my plug screw up pretty damn tight against it! Big hairy 10 or 12 mm head bolt, versus 6mm set screw, head bolt wins, surely! or is there an engineering issue I haven't thought of? (wouldn't be the 1st time!)
    #14
  15. creeper

    creeper Still alive...

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    In a past life, I've seen high grade bolts and studs snap, and I've seen sealing surfaces fail when even a small side load was inadvertently applied... so it's more of a caution against the possibility of something bad happening.

    Heads and cylinders expand and contract... clamp loads can change by several hundred percent.
    A head bolt with a side load could, at worst fail, or at best, do nothing.
    I'm more concerned with the in-between possibility of an altered clamp load and the potential for a resultant gasket failure.
    I can't envision any real advantage to tightening the grub screw down excessively, so to avoid the possibility (slim though it might be) of a problem, I would error on the side of caution and only snug it.

    In a perfect scenario, you could apply sealant to the internal thread in the general area of where the grub screw would rest rather than on the screw itself... to ensure the majority of sealant remains on and around the grub screw threads rather than being dissipated along it's path up the hole.

    All my opinion of course, based on previous experience and a familiarity with the materials in question.

    C
    #15
  16. Zerodog

    Zerodog Long timer

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    You could back out the set screw a little bit after it contacts the head screw. The thread locker will prevent the leak. Loctite 243 would be ideal for this. We use this set screw/ loctite technique in manifolds we build for leaktesting equipment. So.....it seals really well. Great idea.:clap
    #16
  17. funhouse

    funhouse Overdue

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  18. bmwktmbill

    bmwktmbill Traveler

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    Make sure the engine breather hose to frame isn't leaking. it will fool you into thinking the leak is something worse.
    b.
    #18
  19. SFmax

    SFmax Guest

    I love finding the simple fix write-ups in here. I've had a oil leak for some time. In the same exact area. I'm positive it isn't the rocker cover or the head gasket. I also knew I wasn't burning the oil I was supposedly losing and the dirt and grime on my engine generally hid the culprit. I'll happily deal with this issue over the holiday break.

    Thanks guys.
    #19
  20. bbolstad

    bbolstad Adventurer

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    Well, I suspect I've got the same on the 640 supermoto i just bought.
    So, anyone tried to do seal it with the engine still assembled?

    Just do not want to tear it down during riding season :)
    #20