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Strange sound coming from LH cylinder head 8V

Discussion in 'Griso-Bella Chat & Tech' started by klaas123, Apr 27, 2010.

  1. pete roper

    pete roper GT Godfather!

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    I had a 1000Km Stelvio in yesterday I dunno if they have got better at making 'em quiet somehow but certainly most of the *Newer* 8V-ers seem to be. That had a very slight harmonic type noise from the top end. No idea why. didn't consider it an issue, pointed it out to owner, he didn't think it was an issue. Completed service. Sent him on his way. Anyway. Compared to mine his bike is whisper quiet. Mine has always been stupid-noisy. Still goes like a cut cat!

    Pete
     
  2. john zibell

    john zibell Moderator Staff Member GT di Razza Pura

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    Pete,

    How do his end float measurement stack up? They seem a little wide to me, but I don't have an 8V to compare. I would think 4-6 thousands would be more reasonable for the application.
     
  3. pete roper

    pete roper GT Godfather!

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    Didn't measure it as noise wasn't a problem but there was a lot more than 4-6 thou. As I said elsewhere the one cambox/rocker support I've seem was in the 'Reject' bin at the importer's warehouse and while it didn't look significant there was what looked like a casting glitch on one of the rocker shaft thrust faces, (Can't remember which one.) and a very faint witness mark on the side of the casting where the rocker ran. Anyway, replacing the cambox fixed the problem. That's all I know.

    Pete
     
  4. klaas123

    klaas123 Cruisin' Guzzisti

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    I will order a set of shims and give it a try.
    Have two questions:

    What do you consider a safe minimum clearence?

    Do I need to replace the head gasket when the rocker assembly has been removed?
     
  5. pete roper

    pete roper GT Godfather!

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    There are no shims. You'll have to make them.

    pete
     
  6. klaas123

    klaas123 Cruisin' Guzzisti

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    I know Pete but I can order them at a specialized company.
     
  7. pete roper

    pete roper GT Godfather!

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    Before you godown that route try a bearing factor. They usually cover shims with various ID's but for this application the OD would probably be too large. A pair of sharp nail scissors will do the job of clipping 'em down to size. Having said that I am skeptical as to whether end float per-se is the route cause of the problem, if in fact a problem exists.

    With the cyclic noise could it be belt related rather than chain?

    Pete
     
  8. klaas123

    klaas123 Cruisin' Guzzisti

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    Before you godown that route try a bearing factor. They usually cover shims with various ID's but for this application the OD would probably be too large. A pair of sharp nail scissors will do the job of clipping 'em down to size.

    Thanks Pete, will give it a try.

    Having said that I am skeptical as to whether end float per-se is the route cause of the problem, if in fact a problem exists.

    Me to, but I want to rule it out as a possible cause.

    With the cyclic noise could it be belt related rather than chain?

    I'm sure the noise is coming from the LH cylinder, not the front of the engine.
     
  9. klaas123

    klaas123 Cruisin' Guzzisti

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    Had a good conversation (and a couple of beers), with a friend of mine who also happens to be a car mechanic.
    We have come to the conclusion that the rattle is very unlikely to come from the rocker shafts.
    There is no axial force on them and if they were the cause it would be heard permanent, not with the freqency it now appears.
    It has to be cam chain/tensioners related.
    The tensioners can be fairly easy replaced but what about the chain itself?

    Remember the chain has been under great stress, the recall cam shafts came out blue after just 25km. Although everything was fine after the second replacement of the can shafts (at 725km) untill 9000km.
     
  10. pete roper

    pete roper GT Godfather!

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    If the cams had blued severely I'd think the most likely culprit would of been assembley without any assembley lube. Cams and tappets particularly benefit from being liberally slathered in assembley lube! Either that or it was done wrongly and the oil galleries got blocked/misalligned.

    Haven't replaced chains yet. In theory you'd open the timing chest and pull the dummy-shaft forward to unhook the chains and wriggle new ones on somehow. In practice I suspect you'd do it the same way as you do on any other OHC bike. Split the cain, connect a new one to the old one and feed it through and the re-join it.

    Pete
     
  11. klaas123

    klaas123 Cruisin' Guzzisti

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    I agree Pete, that's the only way without removing the engine from the bike.

    Some relevant pictures on the subject can be found inside this document:
    http://www.guzzitek.org/documents/diver ... Course_(GB).pdf

    What would be the proper tool to reconnect the chain? I'm a old school mechanic, never worked with morse chains ha ha
     
  12. pete roper

    pete roper GT Godfather!

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    The way I've always done it is

    Get a hollow bar, (Early Honda Civic rocker spindles are ideal.) and get someone to hold it behind the chain pin. Use a flat ended punch to biff the pin through the outer link. Then use a pin punch to knock the pin out. Don't allow it to fall into the motor.

    Split the *new* chain the same way but make sure you leave the pin engaged with the last outside plate of the chain. Connect new chain to old chain using a loop of stiff wire and wind the chain through the motor using a ratchet on the end of the crank.

    Disconnect old chain and discard. Line up plates of new chain and use multi-grips to squeeze pin through links. Use punch to tap it through the last mm or so so its back *as it should be*. Take something good and solid to use as an anvil and stick it behind the head of the pin on the side from which it has been pressed in from. Get ball-peen hammer and peen over 'Pushed through' end of pin.

    Reassemble. Go ride. Used to take about an hour from Whoa to Go on older jap fours and the like.

    Pete
     
  13. pete roper

    pete roper GT Godfather!

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    OK, another thought.

    The noise could also be associated with the spinning of the tappets. It fits with the cyclic nature of the noise. That too would point to either a tappet or related problem like the cam box that they move in or, perhaps, whether the pushrods are in the right way up.

    It has been clearly specified and reinforced by a service bulletin from the factory that the pushrods are a 'One Way' item. I don't know why, but it might be relevant. Check it.

    http://www.servicemotoguzzi.com/public/ ... 6-2009.pdf

    [​IMG]

    Pete
     
  14. klaas123

    klaas123 Cruisin' Guzzisti

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    Thanks for pointing that out Pete!
    Will closely inspect the cam/rocker area when I'm home from work tonight and will post pictures if any irregularities are found.
     
  15. pete roper

    pete roper GT Godfather!

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    Yeah, well, look at the date on the service bulletin.

    Having said that when I did the cam recall on my POS it was the first time I'd had the cam boxes off. I read the instructions, several times, and then looked at everything VERY CAREFULLY as I took it apart. I noticed the machined rings around the pushrods but could see no reason for them BUT Since they were all aligned the same way I made the rash assumption thare might juts be a reason for it that I didn't understand and when I installed them again I made sure they all went back as before AND I used a shitload of assembley lube

    [​IMG]

    The cyclic nature of the noise exactly matches the sort of noise I'd expect from tappet spin and some sort of irregularity associated with it. As you've said, it isn't every revolution of the crank or the cam. You can try turning the crank by hand and watching the tops of the tappets and how much they move. see how many revolutions it takes for them to complete a full turn, do the maths and work out if it corresponds to the cycle of the noise event. Betcha it'll be close.

    Pete
     
  16. mattin

    mattin Just got it firing!

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    Sounds very logical. If ever the chain tensioner caused the noise what would make it so rythmic?
    Just one comment, kind of old again:
    The right tensioner looks easy to change, or check, but the left one is under the chain and needs that to be removed first.
     
  17. pete roper

    pete roper GT Godfather!

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    That's right! Logical!. It's all down to logic and the laws of physics and engineering. There is no 'White-man-Ju-Ju' or 'Magic Bullet'. I just can't, for the life of me, see why some people seem DETERMINED to find a problem that will neccessitate them taking their entire motorbike to bits. It's just mad.

    It has been established that the cyclic nature of the noise does NOT correspond with crank speed or half crank speed so it is not going to be chain related or therefore tensioner related so why in the name of all that's holy is anybody considering taking the entire top end off the motor. Sorry, this isn't being thorough, it's being STUPID.

    Pete
     
  18. klaas123

    klaas123 Cruisin' Guzzisti

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    [​IMG]

    [​IMG]

    [​IMG]

    Can't find a thing wrong, everything seems in good condition.
     
  19. klaas123

    klaas123 Cruisin' Guzzisti

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    Who said I'm going to take my entire bike apart? Even the gas tank is still in place :lol:
     
  20. pete roper

    pete roper GT Godfather!

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    The lash caps on the ends of the adjusters are comprehensively f@cked! and there is irregular wear on the tappet heads. My guess is that for some reason the *upper* tappet in pic #2 has been not turning correctly, looking at it it appears it may not of been radiused properly or the cambox tunnel it runs in has caused it to 'Grab' at some point. That tappet is showing a clearly defined wear ring where the HLD treatment has been degraded and erroded. You'd probably need more accurate measuring equipment than most of us have to check the radius damage but I'll betcha that the noise is due to the uneven nature of the radius due to the wear on the HLD coating.

    With damage like that to the lash caps you'll never get an accurate valve lash adjustement which will also contribute to the top end noise.

    I'm hoping that the 'I can't see anything wrong' comment was a joke?

    Pete
     

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