Changing the cam chains and balancer shaft bearing

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by kamanya, Jul 6, 2008.

  1. kamanya

    kamanya Andrew to most

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    Ok, major work.

    I have always had a very noisy engine, the cam chains particularly on the right hand side or rear cylinder make quite a bit of noise. The dealers mechanics could never eliminate it or pin it down. I have opened it up a few times myself trying to figure it out.

    Recently I was just passing the bike on the way to get into the cage and whilst staring at the thing I was idly fiddling with the starter button, just pushing it enough to get the engine to turn over but not to fire. Yes it’s a stupid thing to do but… stupid is a stupid does. Suddenly it back fired and something didn’t sound right when it did.

    I started it up and now there was a totally new loud and very worrying valve type noise going on?! :eek1 Something was definitely not right.

    The thought of having to go back in was a bit irritating but, along with fixing this new problem I was determined to find out once and for all what was causing the clatter. As I got into the valves I realised that the front cylinder cams were completely away from where they should have been at TDC. AHHHHH feck! This could be really serious!

    This is what I think had happened; when it backfired there was no oil pressure to keep the cam tensioners tight and in turning backwards the chain had slipped a couple of teeth. When I ran it straight after I did the backfire thing, what I could hear was the valves running totally out from where they should have been. It was possible that the chain may have slipped enough to have the valves hit the top of the piston. So to check this I had to take the head off. This was turning out to be a lot more work than I had anticipated.

    It was at about this time that I decided that if I was going to go this far in I might as well check the lengths of the cam chains too. I really do not believe that my motor is just a “noisy one” and decided that I was going to replace my cam chains and cam chain guides and to try to see if I could not figure this irritation out.

    That got me to here. No damage to the piston or valves, I was lucky.

    [​IMG]

    To get the cam chains out you have to take the balancer shaft out. That’s the shaft above the flywheel/rotor.

    [​IMG]

    To get that shaft out you have to undo this nut.
    [​IMG]

    And this one, the balancer shaft retaining nut.

    [​IMG]

    Both are impossible without locking the engine with the locking bolt.

    Also put the green Loctite on the screws in here so they dont go walkbout.

    [​IMG]


    Once that is off there is a special little torture test getting the two woodruff keys out of the shaft to get the balancer and cam gear off.

    Once I got those off, I finally found what I believe is has been causing the clatter that I get from the engine. This is the left balancer; you can see the rear cylinder cam chain has bitten into it. The wear is all the way around the balancer – deeper where it picks up the chain and less as it turns.

    [​IMG]


    The guide for the above balancers’ chain is the one on the right; you can see that the chain, unlike the one of the left, does not run straight down the guide. There is very slight play in the bearing of the guide (but the play is the same for both).

    [​IMG]

    The locking screw for the balance shaft bearing on the right side of the motor has also seen some wear from the cam chain;

    [​IMG]

    The cam chain for the other side has also worn the balancer although not as bad;

    [​IMG]

    I did check the cam chain tensioners and the length of the spring that regulates the oil pressure. All were in spec. Ultimately what happens is that for some reason the cam chains operate very close to the balancers. The balancer clips the chain and causes the perpendicular flutter that cannot be damped by the tensioner and causes the cam chain clatter that can be heard at lower revs. It also sets up some horizontal movement that then bites into the bearing retainer screw.

    I consulted with the head of technical services for KTM in South Africa. He was pretty helpful and suggested after chatting to the propeller heads in Austria that the balancer shaft bearing may be at fault and I need to get them out. They think that the shaft has more play left and right than it should have and the left hand bearing is supposed to prevent this.


    How do you get the left balancer shaft bearing out? Good question. That’s the one next to the worn screw in the above picture. There are some expensive solutions that call for splitting the cases or bearing pullers but a simple method is…. A broom stick! The left hand bearing... the one above the crankshaft here

    [​IMG]

    has a bigger inside diameter than the right (the one I wanted out) and amazingly I happen to have a broom stick that happened to be the right diameter to fit through the above bearing yet not the right and I could drive the right hand bearing out from the left hand side. A word of caution though…

    This left bearing has a race in it that has a lip on the engine side of it that prevents the race from falling out.

    [​IMG]
    [​IMG]

    There is a retaining lip on the inside of the case that stops the race from coming into the engine. This retaining lip does not run the whole way round, it is a half moon. When I drove the bearing out the race got stuck on the broom stick. I didn’t see this as a problem as all I had to do was now drive the broomstick out the race. What I should have done was pull the stick all the way through and pull off the race. But I just gave it a few taps. The race came off the broom and promptly fell into the crank case. This happened because the case lip does not go the whole way around the case. The race once it came off the broomstick, fell into the case. :eek1 :dog :baldy So there I was swearing that I had a race sitting somewhere deep in the bowels in-between the cranks somewhere. It is a very depressing predicament to be in. Fortunately for me I had already taken the front cylinder head off. So I was lucky in that by turning the front cylinder to TDC and pulling the barrel up a bit I could see the race nestled at the bottom of the crankshafts and it was easy to hook it out. You don’t want to have to do this.

    The bearing had quite a bit of lateral play in it. So I think that the balancer shaft was able to move laterally, this causes the balancers to catch the cam chains and causes the clatter. What I think is the cause is that the bearing had not been pushed in far enough and had not seated properly. this allows the race too much play and thus the shaft can move too much and causes the cam chain flutter when the balancers nick the cam chain.

    Those bearings are expensive. But then anything with a KTM sticker is. In hindsight the old bearing is fine, it just needed to be driven in a bit more. Ahh well I now have a new bearing in there.

    Now that that had been changed, to the cam chains

    Old vs new one. Interestingly I couldn’t find any wear marks on the chain from hitting the balancer. They both are markedly longer than the replacement ones.

    Rear cam chain with replacement
    [​IMG]

    Front cam chain with replacement
    [​IMG]

    I also bought a pair of the longer tensioner bolts, they are about 5mm longer, sorry I didn’t take a pic of them. (edit - here you go)

    [​IMG]

    [​IMG]

    Putting everything back together went smoothly. I turned the engine over a few times to see if everything was sounding as it should, then hooked up some petrol and turned on the ignition. No fuel pump noise?

    This might be the problem.

    [​IMG]

    [​IMG]

    I cleaned it up as best I could and got it running again but I am going to have to get a new one.

    Once that was fixed, hit the starter and it fired right up.

    And bonus of all bonuses, it purrs smooth as silk with not a rattle or a clatter to be heard. It doesn’t even make the normal cam chain noise at startup.

    Lastly I put some grip warmers and two new HID's in - its quite a squeeze to get it all in there. Had to move the hooter.

    [​IMG]

    They are really really bright, I can't wait to try them in the dark.

    [​IMG]

    I went for a ride today and even the rain couldn't keep the smile from my face.

    [​IMG]

    I am in love again.
    #1
  2. PABiker

    PABiker Anywhere but here

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    Nice work.:clap
    #2
  3. adiablolex

    adiablolex Lost again

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    more of an awesome investigative report if you ask me.
    How many K's on the bike ?
    #3
  4. Steffo

    Steffo Been here awhile

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    Wish I had the skills, and the guts, to do surgery like that. I just started my "med school" with installing the 12V Outlet and the KTM Alarm on my 950.
    #4
  5. markjenn

    markjenn Long timer

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    Great work and great attitude. You really worked through some thorny issues that would have most of us tearing our hair out.

    - Mark
    #5
  6. Steffo

    Steffo Been here awhile

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    ..and crying like little girls at that. :cry
    #6
  7. kamanya

    kamanya Andrew to most

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    29000km. It is an 04 model.

    Most of them have been ridden pretty hard.
    #7
  8. adiablolex

    adiablolex Lost again

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    reason I asked cause mine is an Ofour 23k, think I'll get into her in the winter as a preventative measure. Are those longer plugs for the tensioners an upgrade? I know some noise is normal but this is not my kind of normal noise.:thumb
    #8
  9. ADVJake

    ADVJake ***** dweller

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    That same noiise is what Mudguts and I are getting.
    So we have to replace balancer shaft bearings & the cam chains too?
    Only at 35,000kms :eek1
    #9
  10. adiablolex

    adiablolex Lost again

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    I don't know if the new chains are redesigned but the way Kamanaya is comparing the two side by side seems like there's a bit too much stretching going on.
    Any of you guys try the longer cap bolts for the tensioners?
    I'm throwing the idea around to put something there so the chains don't rattle loose as they fill up with oil.
    #10
  11. cpmodem

    cpmodem Orange Caveman

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    Sounds from kamanya's excellent article that this was caused by an improperly installed bearing. Not likely to be a systemic problem.
    #11
  12. gefr

    gefr Life is a trip

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    As I realized watching my technician working on one. How do you take it out? Do you hit it with a hammer from the back side or do you pull it with an extractor tool? Cheers.
    #12
  13. kamanya

    kamanya Andrew to most

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    Mine came out pretty easliy with a few whacks from a rubber hammer. I dont think you can pull it out by hand, it is pretty tight. The manual says,

    #13
  14. kamanya

    kamanya Andrew to most

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    The balancer shaft bearing I think will be fine, if it is not seated properly then evidence of this will be on the balancers where they catch the cam chains.

    Mine on occasion had a good clatter going and it was distinct from just cam chain rattle. This clatter when it did happen was not just on start-up but anytime the revs dropped. What baffled me was I just had the rattle and occasionally the rattle and the clatter.

    Now I know that the clatter happened when the shaft had moved.

    Because of this, I presume that the cam chains were prematurely aged and stretched.

    If when you check yours cam system, if you can get more than a 2mm of play (mine had about 5mm) from the race then you need to drive the bearing in to properly seat it. Of course take care when you drive it in not to damage the bearing.

    Also, when putting the balancer shaft back, I can imagine that there is a chance that when tapping in the shaft that it moves the bearing out again if you haven't put the bearing locking screw back.

    [​IMG]


    The cam chains are exactly the same in type, the only difference I could see apart from the wear was that the old ones had a single letter stamped on it - can't remember now but I can go look when I am back home. The new ones had "DID" and a few other things stamped on them.
    #14
  15. kamanya

    kamanya Andrew to most

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    The longer tensioner bolts are an upgrade that comes from KTM. The part number is 60036008100.

    Getting the bolts for the older engines might be something that gets a few more miles out of your cam chains. But unless you have the issue I had I think they should be fine for a fairly long time.

    I don't know why so many older engines are noisy and none of the newer ones are? They must have changed something. If you look at what is in the older and newer engines they use exaclty the same chains, tensioners and guides. What is diferent is what they call a "spreader gear" in place of the timing gear on the end of the balancer shaft on the clutch side. This must be what makes the difference. How, I don't know?
    #15
  16. uk_mouse

    uk_mouse Aquatic adventurer

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    I heard thatthe oil pump was upgraded in later engines - a bit more oil pressure would reduce the clatter somewhat.
    #16
  17. cpmodem

    cpmodem Orange Caveman

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    The oil pump is the same part for all of the years, butt the bypass control piston was changed in the very early days (engines prior to #00773).

    The split balancer/camchain drive gears were added on the 2005 models with a redesigned balancer. I suspect the spilt gears were an effort to quiet the engine to help pass ever more stringent ECU noise tests, butt undoubtedly did result in a less "mechanical" sounding LC8 engine.

    Over the years, "improvements" in several areas were added that resulted in even less "noisey" engines (and bikes) overall.
    Soon, with the addition of rubber coated trans gears and a driveshaft upgrade, the big Katoom will be as silent as the Bee-Hemm-Doobya :D
    #17
  18. YOGOI

    YOGOI Prick

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    Thanks Kamanya!!!!!!!!!!!!!!!!!!!!!!!:thumb

    CP. Is this "HOW" material or what???

    Again, Thanks Kamanya. Its nice to read a thread like that. Good attitude, and knowlage. :beer
    #18
  19. cpmodem

    cpmodem Orange Caveman

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    I'm all over it YOGOI :freaky
    http://www.ktm950.info/how/Cam/camchain_noise/noise.html

    As usual, kamanya has done a bangup job of illustration and narrative :webers
    #19
  20. HellsAlien

    HellsAlien a has-been that never-was

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    Kam,
    I had similar experience to yours in late '06 on my freshly/comepletely rebuilt 950. A metallic "tinkle" from new motor after about 2 tanks of gas.

    The balance weight was moving axially on the jackshaft and rubbing the stuff on the case just as you have shown. This movement allowed partial dis-engagement of the woodruff key that drives the balance weight. That lead to slop in the jackshaft keyway. Solution: replace the jackshaft, balance weight and associated detail parts.

    In late '06 the new jackshaft showed up. It wouldn't fit because there had been a running change to the shaft that enlarged the bearing journal on the shaft a couple of mm. Called KTM tech. Find out that we need to order kit P/N's that entail new bearings.

    Oh, and another part, a special shaft spacer that does not appear on any parts list or TSB (at least at that time). This spacer, about 2 or 3 mm thick, is what keeps the backside of the balance weight from striking the case and making the noise. It was supposed to ship out with every "new" jackshaft, but that didn't happen 'cause the jackshaft p/n's were still the same. There was no way KTM USA could keep track of the updated shafts w/spacer.

    At the time, the revised "large journal" balance shaft had the same P/N as the old (60036073000) hence there was no way we could know that it was only interchangeable as a shaft/bearing/flyweight kit. Was very frustrating for the mechanic, as he really was/is good at his job. This was not his fault, nor the fault of KTM USA. The mechanic only knew of this because he recalled a "special spacer" being mentioned in one of the trainings his dealer had sent him to. No substitute for a good shop w/ a good mechanic who's paying attention & taking notes!

    Once aware of this it went OK, but at the time none of this was written down from KTM, had to know who to call about exactly what. The only clue (after KTM tech chat) is different bearing p/n (book part 9 is now 60030024100) & different balance weight (60036074150). I have never seen a p/n for the shaft spacer behind the balance weight. This was part of a running factory change in '06, I believe.

    I suspect that the part you refer to as "spreader gear" may have the spacer function built-in now, that would make sense, but I can't say for sure.

    Perhaps older bikes with the "tinkle" could be fixed with a simple home made spacer behind the balance weight, assuming all the shaft/keyways/keys check out OK?

    End of KTM history lesson for the day, lets go ride! :D
    #20