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Clutch thrust bearing on 8V's

Discussion in 'CARC' started by pete roper, Nov 21, 2011.

  1. pete roper

    pete roper GT Godfather!

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    The factory released a service bulletin a few months back about the thrust bearing on some 8V's most notably early Stelvios and Grisos becomming noisy in service. While no further explanation was really given it was obvious that the bearings were failing in some cases and the sollution was said to be to replace the whole thrust assembley with a new one with two bearings that has a superceeded part number to the original.

    Now MarkIII who posts here was having some problems with his clutch on his 8VG, we found out last week that they were in fact unconnected with the thrust issue but since it was something that had been mentioned by the factory I went ahead and ordered the new part that comes as a complete assembly, supposedly a new thrust cup and two bearings. Well, they weren't in stock so they went on BO and duly arrived a couple of week later. Unfortunately they only has ONE bearing in the kit!!!! :roll:

    Last week when we pulled the swingarm on Mark's bike to get at the slave cylinder and thrust mechanism we found no problem with his thrust mechanism but in for a penny? In for a pound! We used the original bearing and the new one as shown on the service bulletin. His clutch pushrod length was correct but interestingly, even though adding another bearing effectively increases the length of the thrust mechanism by 4mm there is no suggestion that anything else in the system needs altering.

    This is by the by, the whole thing went back together fine and we then found the source of the problem that Mark said he'd probably post about but I'd also bought a second thrust assembley to put in stock and today did a bit of measuring only to find that the actual thrust cup is identical to the 'Old' one, hence the extra length in the mechanism which means that rather than buying the $80 assembley from Guzzi all one actually NEEDS to do if you want to add another bearing is go to the bearing factor and purchase a 10 x 24 x 4 Torrington and while I have yet to purchase one it'll sure as shit be cheaper than $80 :mrgreen:

    Pete
     
  2. DanPez

    DanPez Cruisin' Guzzisti

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    The symptoms would only be if the lever starts to get hard to pull right?



    Are there supposed to be 3 bearing in all?
     

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  3. pete roper

    pete roper GT Godfather!

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    That pic shows one bearing and two races. With the new set up you end up with a second bearing piggy-backed on the first so you get race, bearing, race, bearing, race.

    Pete
     
  4. Phang

    Phang Cruisin' Guzzisti GT Contributor

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    So there is more than 4mm (bearing + race) introduced to the total length of the assembly?

    I am quite surprise to learn that the clutch actuation assembly can accommodate the extra 4mm+

    As the clutch push rod came in 4 lengths with 1.5mm increments, which I think allowing a +/- 1.5mm error. Wouldn’t the additional 4mm in the thrust bearing pack preload the pushrod?

    Phang

    [​IMG]
     
  5. pete roper

    pete roper GT Godfather!

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    I think that the different rod lengths are there to compensate for different diaphragm spring preloads due to manufacuring tollerances rather than the abillity of the slave cylinder to cope with extra travel.

    I could be completely wrong on that. The addition of an extra bearing will be for speed reasons rather than load but all I can immagine is that people who slip their clutches alot would be more likely to experience problems with the single bearing set up than the twin.

    Pete
     
  6. Phang

    Phang Cruisin' Guzzisti GT Contributor

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    It make sense Pete [​IMG]

    Do the later machines come with twin bearing setup :?:

    Phang
     
  7. pete roper

    pete roper GT Godfather!

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    Buggered if I know? Never had a look at one. I'd say a cautios *Maybe* on that. Given past history on 'Updates' the world is your oyster.....

    Pete
     
  8. pedmondson

    pedmondson Just got it firing!

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    I believe I have the same issue "thrust bearings". Is the main symptom a high pitch whinning sound coming from the area around the alternator?

    It happens to me when I come off throttle. If I change gears while this sound is being made, the sounds stops.

    Thanks,

    Patric
     
  9. pete roper

    pete roper GT Godfather!

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    Thrust bearings are at the back of the gearbox. Logic would dictate that if there is a bearing noise from the region of the alternator it is most likely to be an alternator bearing. Having said that what you'te describing has the symptoms of belt slip. Have you checked the tension of your belt?

    Pete
     
  10. diedel

    diedel Tuned and Synch'ed

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    Pete,

    may i resurrect this topic? While disassembling swing arm for grease check I took the opportunity to check the clutch thrust bearing, too. While inserting gears my late 2010 Griso Tenni made from day one on very heavy "clonks" esp. when getting warmer. This even get's a little bit worse after now 14.000 Km. What i'm asking me, if it will help to pack up the clutch thrust with one more bearing in a sense of a precautionary action or say "can not harm". I have sufficient new bearings/races at hand…
     
  11. pete roper

    pete roper GT Godfather!

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    Adding another bearing will make absolutely no difference to how it changes gears or how much it 'Clonks' when you select a different ratio.

    The 8V six speeds don't have a driveline shock absorber in the gearbox or rear wheel. They are always going to be noisy. Removing as much play as possible from the throttle cables makes throttle control more sensitive and will help minimise the racket but really its a matter of practice makes perfect.

    Quite early in the piece there was a rash of failures of thrust bearings in Europe, (Why is it always in Europe?) and for some reason the factory suggested adding another bearing. I've never understood why as having another bearing won't reduce the pressure, only the speed at which it runs. Since then and long before your bike was built the clutch was re-designed with a lighter spring so the bearing is loaded less. There is also the fact that by adding another bearing you effectively alter the length of the pushrod so unless you have the pushrod length calibrating tool and all four pushrods you could be making a 'Rod' for your own back. (sorry for the dreadful pun!)

    My advice? Leave it alone!

    Pete
     
  12. diedel

    diedel Tuned and Synch'ed

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    Thank you for your fast and comprehensive advice, it helps me a lot!

    Dietrich
     
  13. Stella

    Stella Tuned and Synch'ed

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    I'm replacing my thrust bearing with a double bearing set up soon, what ,if any, grease are you supposed to use in the thrust bearing ? Can't find any info in the service manual regarding greasing this bearing.
    Thanks
     
  14. john zibell

    john zibell Moderator Staff Member GT Founder!

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    The bearing is lubricated by the gearbox oil. I would just apply some oil to it on installation.
     
  15. Stella

    Stella Tuned and Synch'ed

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    Ok, that makes sense , thanks for the tip,still have much to learn about my "Stella"
     
  16. leafman60

    leafman60 Cruisin' Guzzisti

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    Can anyone provide more information about the infamous double bearing tech bulletin? What engine numbers did this affect?
    I cannot quite figure the logic in this "fix." If there was a bearing problem, I would think simply replacing the one bearing would be the fix. Also, do the new 8V's come with two of these bearings or one?
    Regarding the added length to the pushing mechanism that the extra bearing creates, there may be a "stop" on the pushrod intermediate piece that delegates added clutch pressure only to the pushrod and not the added items between the slave cylinder and the pushrod assembly.
    I'd like to know more about this. With my bike closing in on 35,000 miles, I may be noticing some wear or breaking-in of my pushrod assembly and need to add one of great length. I have no bearing noise or clutch groan etc., though.
     
  17. GT-Rx®

    GT-Rx® Administrator Staff Member

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    With the Tech Bulletin info being NLA online, tough to say. I don't think any of the VIN's were documented that I am aware of. I would say the bearings are very long life... close to 100k miles or more. That said, if you're in there, couldn't hurt to replace them I suppose.
    My guess as to length difference is that since it's a hydraulic system/slave cylinder, the slave simply is able to absorb the difference. I would peruse the parts lists between the older and newer versions. Post on what you find out.
     
  18. brodonn

    brodonn Just got it firing! GT Famiglia

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    May I, instigate a re-resurrection of this topic.
    After my Son lost clutch pressure on his 2010 Norge (actually probably manufactured in late 2009) we dismantled the rear end and removed the slave cylinder, confirming the leak that we suspected existed. The cause of the leak was actually that the thrust bearing had disintegrated and the thrust cylinder that acts upon it had begun to rotate, causing the piston of the slave cylinder to rotate and cause damage to the wall of the piston housing.
    O.K. we thought. We'll simply pull out the old bearing, with it's washers and replace the assembly, including the thrust cylinder and slave cylinder. Easy? No? Because the manual says that the bearing assembly comes out of the bore towards the rear of the bike, and backs this up with a picture. Not so, however. It turns out that the outer washer of the bearing assy has a smaller diameter than the bearing race, so that it comes out to the rear but the race doesn't. This means that we now must remove the engine, in order to remove the gearbox which we'll have to open to remove the thrust bearing race (or what remains of it).
    Sorry for being so long-winded, but I was wondering if someone who has replaced their thrust bearing could tell me what the outer diameter was/is, and also of the washers? Reading previous posts, the temptation is to source a bearing assy of 22 mm O.D. (not really a standard size) and fit it against the remains of the old race, and avoid all the work. Not really a good engineering solution though.
    Any advice or opinions greatly appreciated.
    Brian

    P.S. I have just read a post by Pete that gives the part no.s of the bearings and I see that it's 24 mm O.D. The bore to the rear of this gearbox is 22 mm and this was the diameter of the outer washer. The race is positioned beyond a step in the bore where it becomes 24 mm. I don't like this as an arrangement, apart at all from it causing me to have to remove the gearbox

    Brian
     
    Last edited: May 19, 2017
  19. john zibell

    john zibell Moderator Staff Member GT Founder!

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    This is crazy design. Time to shoot the engineer that designed this.
     

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