Tips for a first-timer doing a 950 head rebuild

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by Jdeks, Apr 21, 2014.

  1. Jdeks

    Jdeks Accepting and supportive of everyones feelings.

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    Okay,

    So I've decided to bite the bullet, and refresh the heads on my 100k old '04 950.

    I know the valve stem seals need replacing. But I plan to have the valves lapped, cylinder re-honed, replace the cam chains, tension rails, rings, head gaskets and anything else that's sensible while I'm down there.

    I've never done something this big before. I plan to follow the workshop manual, which I have, and any relevant bits from the HoW and ktm950.info.

    But could anyone else who's done this job possibly offer some advice?


    • What exactly IS 'valve lapping', and how do I do it? Give it to a shop?
    • Same for cylinder honing?
    • How exactly do I replace piston rings? Is there a special procedure? Or just take the old ones off, and put the new ones on?
    • What else should I do/replace while I'm down there?
    • Any other tips or gotchas I should be aware of?
    Cheers. :freaky
    #1
  2. chasbo

    chasbo Long timer

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    Good luck on your rebuild!
    #2
  3. Chop Chop

    Chop Chop Hector erector

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    Still putting mine back together and no expert, so others can comment on stuff I have obviously missed and may need to rectify.
    #3
  4. MacMan

    MacMan Been here awhile

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    The process will take as long as it takes, but don't skimp on having everything measured properly.

    You may find that the bores are actually very good. Nikasil is like that - so long as the engine has never ingested dirty air or water, the pistons and rings cop the brunt of wear.

    Pistons almost certainly will need replacement, rings definitely.

    At that sort of mileage, the valves will need thorough inspection and measurement including looking for stem wear. If they're out of spec the guides will be too.

    Find a good machinist and pay what they ask to do a good job because a bad job is worse than none at all, and that's before you factor in what it cost. Just touching up the seats yourself is pointless if there are other wear issues.

    Have fun. You'll learn a lot. Oh, and be clean :D.
    #4
  5. Dr AT

    Dr AT Long timer

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    Rohan, perhaps book some leave, ask fozzie if you can watch him do the work +/- spend some time watching him do other jobs?
    #5
  6. StevenD

    StevenD Hmmmm, dirt!

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    would not supprise me if the pistons are good still, but yeah, measurement is required.
    For the valves, just a suction and paste job will not do in most cases. Re-grinding at the correct angles and width is what you need to make it like new again on the seating area.

    take your time and make friends at a good engine shop.
    #6
  7. Jdeks

    Jdeks Accepting and supportive of everyones feelings.

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    This is an issue.

    My living situation means my 'shed' is a communal storage shed out the back of the units, which I have been told NOT to clean out, despite having a good layer of dust and cobwebs.

    Even if I did, it's literally a tin shed in a carpark. Air tight it aint, and theres construction machinery and mowers in the area on a semi regular basis.

    Is this a deal breaker in its own right?
    #7
  8. MacMan

    MacMan Been here awhile

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    [​IMG]

    There are ways around any problem.
    #8
  9. Bowber

    Bowber Been here awhile

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    I've never worked on the 950 beyond basic maintenance and inside the side covers but I've rebuilt and tuned racing engines for years.
    A clean working environment is a must. A speck of dust isn't a problem but having dust blowing around and sticking to all the oily parts as you rebuild is a problem.
    If you can not work in a clean environment your better off not doing the rebuild at all if the motor is running ok and not using loads of oil.
    Take the heads and barrels off and then seal up the motor with bags and tape, then take the heads to somewhere clean to work on them.
    You may need new valves and guides but measuring everything will tell you.
    Old valves will need regrinding and the seats need cutting by a competent person with the proper equipment, then you can finish with a light lap to make sure they seal but if the seat cut and valve grind is done properly then they shouldn't need lapping.
    I'd look at rings, valve seals and probably valves at a minimum with that mileage, nothing worse than a rebuild only to drop a valve a few months later but it depends on how hard the motor has been used.
    Valve spring length will need checking as well as they settle just like any spring.
    Hope that helps

    Steve
    #9
  10. COXR650L

    COXR650L Long timer

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    What symptoms are you having that makes you think the top end needs to be torn apart?



    Im just finishing up a rebuild on my 04'. My plan was similar to yours and just do the top end, however I went ahead and cracked the case. At 80k miles the main bearings were shot.

    A lot of people say the bottom end will go forever (and Im sure I could have got several more miles out of mine) but there is no denying the bearing were worn towards the end of their life. At 100k I would bet you will be needing them as well and the reality is you will be in this overhaul close to $1k for the top end. It would be a mistake to not address the bottom end and waist all the money and risk trashing the engine with a bottom end issue 1 year down the road.

    My advise, you are just wasting time and money pulling the engine and doing the top end without at least looking at the bottom end. FWIW.


    For my rebuild I spent about $1700 and skipped over stuff I should have addressed but did not have the money for. $2500 would be the bare minimum for a "complete" rebuild on an 04 if you did the work yourself.

    On that note:
    I think you need to plan for a lot more top end maintenance at 100k, you may get away with less but understand the following may very well need to be done once you get in there and the cost will raise very fast:
    -New valves/spings/guides/head work
    -New pistons
    -New cylinders



    If I had to do it again, and especially coming in the spring riding season, I would buy a low mileage used engine:deal

    Good luck.
    #10
  11. dirtbikebagger

    dirtbikebagger Adventurer

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    Honestly a dirty location and first time engine work both sound pretty sketchy to me. Headwork will likely cost you a grand or more. Without all of the proper measuring and machining tools you basically have to bring it all (jugs pistons heads lower end) to a machinist and say "make it fit". Then you just pick it up and assemble the engine.
    I would be leaning towards a used low mileage 990 engine on ebay! Cant beat a factory built stock engine.
    #11
  12. crofrog

    crofrog Long timer

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    I'd also _seriously_ consider just getting a low mileage used 990 motor off ebay.
    #12
  13. Qwik

    Qwik Adrenaline Addict

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    I found my 950 replacement engine for $1200. Hell of a lot cheaper than a head rebuild.
    #13
  14. Jdeks

    Jdeks Accepting and supportive of everyones feelings.

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    Thanks heaps everyone :clap

    I should first clarify - it's 100 000 km, so only about 60 000 miles.

    I'm getting a puff of smoke if I blip it in neutral, and signs of leaky valve stem seals (engine break down a hill and hit WOT, big cloud of smoke). Doesn't blow visible smoke otherwise during running, but oil consumption at about 500mL in 3000km (2000 miles).

    Also finding the cam chain clatter is taking a bit longer to go away than it used to, and this is with the longer tensioner bolts.

    Aside from that, it makes good power and runs like a clock. In all honesty I could keep riding it as is for a while, but winter is here now, and I have a BIG trip planned in the near future, so I don't want any unknowns.

    Cam chains and sliders can be done with the engine in the frame (albeit with a bit of fiddling). But from what I know, to replace valve stem seals, you pretty much have to pull the head. I figured if I'm doing that I may as well go whole hog and rebuild the head, even if it is premature. I figured the bottom end would be right to leave though, based on reports of its longevity.

    If there is a way to replace the valve stem seals without pulling the heads, then I'd probably just do that, replace cam chains and sliders, and keep riding.



    Yep. I've had several other people say this to me already. Seemes to be the done thing, actually. Not being in the USA, 990 motors are a little bit harder to come by here, but its still a feasible plan.

    I guess I'm just sentimental about keeping my faithful motor going, and I also kinda want the learning experience.

    But by the looks of things, it does seem a right daft thing to do, especially considering how much I'd have to pay to get all the machining done....
    #14
  15. AJ990R

    AJ990R motorcycle guy

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    JDEKS,
    -You've got the right idea. Your motor IS NOT used up & in need of replacement:deal Replacing the engine is the easy way out IMO. You MOST LIKELY just need some intake valve seals cause the rubber is now hard as as a rock.
    Not sure how mechanically inclined you are...or if you got an air compressor.
    -Someones had to have done this!??
    -A standard leak down tester adaptor to spark plug thread, hold the motor on a top of compression stroke, compress the spring somehow(usually requires a quick tap from a hammer, get extra keepers!), and change the seal with the head still installed...done time & time again in the automotive world(esp V8 BMWs).
    -Only issue I see is the little valves for the motorcycle vs a car. Tried to gooogle it, can only find automotive "in head" compressors. You can easily cut up 3/8 deep sockets to work with small valves, but homemade special tools would require a welder...
    -Not the end of the world to drop the motor for head/jug removal.(IF it ain't broke don't fix it!)
    -Don't give up on her yet:deal

    CHEERS
    AJ
    #15
  16. Head2Wind

    Head2Wind MotorcycleMayhem

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    It requires a special tool to compress the valve springs to then release the keepers/spring retainers.... Not a overly expensive tool.

    1. Engine has to come out
    2. Cylinders have to come off with the heads
    3. Clean environment is very important!
    4. Unless you absolutely need 'the experience of rebuilding my own machine' I suggest that you pull the engine and take/ship it to someone who has the tools and experience....

    This engine is not overly complex or extremely difficult to work on, however it does have its 'secrets'. Of all of them that I have worked on, only 3 of them have I done required head/valve work on. Most of the major work has been as a result of failed head gaskets. I would also not 'lap' the valves on this engine _IF_ installing new valves into correctly cut seats. A modern 5-7 angle and/or blended bowl work do not require (nor do many high end engine builders recommend it either) a 'lap' in of the valve/seat.
    #16
  17. COXR650L

    COXR650L Long timer

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    oooo.....Well thats a little different. Damn metric system:lol3 At 60k I would guess cleaning up the valves and rings is all you'll need to do.


    It it were me I would still crack the cases and check the bottom nend if the engine is out of the bike and you have the top end torn apart. It will cost about $75 more for a complete KTM gasket kit and 2 hours of your time. I know people SWEAR these engines go forever and are willing to throw caution to the wind and not even verify the condition of critical components when you have the perfect opportunity :confused.

    60k is not a new engine (especially given the symptoms your having) and I still say you've gone this far just take a look for peace of mind, chances are it will be fine but are you willing to risk that for so little upfront effort and money? While you are in there you can update the oil rail ($.99 part:wink:) do the shift fork bushings and the shift drum if so inclined. Hell if you have the money just spend 300 or so and replace the main bearings and have a completely fresh engine that will be good for another 60+k without worry.

    Edit: I maybe I missed it but if you said you don't have a good place to work on it or many tools...just re ring it, new valve stem seals and ride it!
    #17
  18. desert sky

    desert sky Adventurer

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    Glad to see you rode the new and decided to rebuild the old. My thoughts are if you do any engine work, do it all. I did a valve only job on a high mileage car engine once. With the enhance sealing in the head, I really found out how bad the pistons, rings and cylinders were. What ever I gained in the heads was lost as blow-by in the cylinders.

    I also agree with the inmate who recommended you remove the engine and take it to a good rebuild area. ds
    #18
  19. Zuber

    Zuber Zoob

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    I've seen a few LC8's of that year and mileage, break a ring. It starts blowing oil and after a while running poor on one cylinder. Run it too long and you need the cylinder re-coated to match a new piston. About $150 over here and $500 for a piston kit.

    Do not lap the valves. You'll just make them worse. Cut the seats, grind the valves or replace.

    Comments on wear. KTM's have very tough valve guides. They are rarely out of spec. This engine has plan bearings in the crank rods and mains. If you kept oil in it, you probably have very little wear at 60k miles.

    Pull the engine and carry it into your house. It's light at 125 lbs.

    CLEAN, CLEAN, CLEAN. Engines usually get the most dirt in them when opened up.
    #19
  20. stupot

    stupot Been here awhile

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    Are you sure the valve seats are passing oil? My 04 with 15k was blowing a oil whilst in neutral. After some research on here and asking questions it turned out to be the balance shaft seal.

    Have you checked the carb buckets for oil?

    I order a new seal and the one way valve with goes on to the breather pipe. cost me less than £30 - no more blue smoke.
    #20