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  1. #1
    i will get all the rest i need when im dead corkycat's Avatar
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    I think this answers why the clutches are failing!!

    Hey guys I think I have found the route problem with the supercharger clutch failiures, my clutch failed at 67 hrs while jumping of the wake of a boat, the wake was minimal and I think the problem with the clutch was a substantial part that played in the fail that happened, please bear with me while I upload photos and detail of the flawed parts. I feel strongly that the info I am giving here is correct as I work with different metals offshore on oilrigs so have a metal fatigue background.

    Firstly I waited 4 weeks for parts to arrive in this time I removed the charger, oil pump and parts ready for the removal of the clutch. (there will be a full separate thread on the stripdown and rebuild)
    Once the parts arrived I removed the new clutch from the bag to inspect, upon first look I suspected that the design was poor, but on further inspection this system appears to be a good design once the clutch is in place. Now here is the thing, once I removed the clutch assembly from the ski and wipped the oil resedue from it I could see a slight putty like discoloured substance within the metal parts of the clutch housing, I then removed the locking ring for the clutch and removed the crank drive gear. There was a few very small metal fragments (maybe 4 or 5) this was obviously breakdown from the point of failiure, all sprags within the clutch mech itself were set at an angle locking the clutch itself in free wheel (this in my opinion was a good thing as apossed to other people that have had parts shatter)
    Now please bear with me while I upload photos and a description detailing what i think is the weak link here,
    Click image for larger version. 

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    so here is a pic of the clutch assembly with the drive gear removed

    Click image for larger version. 

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    here is a pic of the clutch assembly, can you see the fragments? but these i feel are the result from the fail on the day and not related to the root failiure.

    Click image for larger version. 

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    this photo shows the sprags as you can see they have gone way past their free wheel position


  2. #2
    i will get all the rest i need when im dead corkycat's Avatar
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    update of pics

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    here is the sprag parts that fell out of the clutch and the ones that remained in i was able to remove with ease by hand
    Click image for larger version. 

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    Click image for larger version. 

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    now look carefully at this pic, this shows the inner cage of the clutch this is the point that everything starts to become apparent, although you cant see it very good on the pic each hole where the sprag sits apears to be slightly out of shape from the sprag leaning on the wall of it...so obviously this is the cause right??? wrong!! there is more

  3. #3
    Antiguan FZR's Avatar
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    Your links are not working

  4. #4
    i will get all the rest i need when im dead corkycat's Avatar
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    getting there

    Click image for larger version. 

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    take a look at the shaft here and more so the next photo

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    do you see the pitting this is a result of both metals rubbing together, wich is obviously the design of the clutch but heres the thing, the sprags are the weaker metal and are rubbing to a point and then all of a sudden when the metal on the sprags gets to a point where it can lock and bite this is where the clutch fails , just look at the bite marks in the shaft hence the first photos of the sprags bending right the way over and going past neutral position thus giving no clutch
    Click image for larger version. 

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    this shows where the sprags have been kicked right over in the housing marking the outer housing
    Last edited by corkycat; 06-26-2010 at 03:29 PM. Reason: getting there

  5. #5

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    This wearing of the surfaces where the sprag bearing run on is why you should NOT replace JUST the sprag bearing only and the WHOLE sprag bearing assembly should be replaced any time you have a failure. I am still not convinced that some of the aftermarket oils that you guys are using just don't work too good when used in a sprag friction bearing set up and may cause the sprag to slip at times instead of locking up. Some of these oils have a lot of friction addatives as well as other addatives in them which IMO can cause the sprag to slip instead of lock up. Just my .02 cents worth, Tommy Jordan

  6. #6
    i will get all the rest i need when im dead corkycat's Avatar
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    Click image for larger version. 

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    right here in my opinion is the problem, take a look at these sprags, these are designed and shaped so they let the shaft roll one way and they lock onto the shaft the other way, now look carefully at these, can you see the filling of the sprag. this rolls on the drive gear shaft and is the side that locks so the supercharger engages and you get boost. these sides of the sprag are shanfered to a point but are still rounded of so they can roll with the shaft, look at the 3 pics above the shaft has worn the sprags flat to a point

  7. #7
    i will get all the rest i need when im dead corkycat's Avatar
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    Click image for larger version. 

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    this pic shows the new sprag clutch, notice the sprags are rounded off
    so basically what im saying here is in my opinion i think the sprags need updating to a harder metal to make them last a bit longer, as soon as the sprags rub to an extent that they have a flat surface then this allows the clutch to bite letting it fold and then all the sprags act like dominoes folding over past the neutral position busting the clutch
    just my very long 2p
    and i dont think types of oil will make a difference, i will bet my bottom dollar that when an upgrade comes out the sprags will be made of different metal

  8. #8

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    When the sprag bearing roller trys to lock aginst the mating surface and it slips instead of locking up tight this causes wear to the roller and it's mating surface this wear is what you are showing in your pictures of the bearing and the surface it runs on. Most of the time this is caused by more load being put on the sprag bearing than it is designed to handle and it slips in the lock up direction. I hope that Yamaha will see enough warranty claims and customer complants that they will up grade this sprag in the future! Any oil that has friction reduction addatives in it tend to cause the sprag to slip since friction agenst it's running surface is what causes it to lock one way only, Think about it! Tommy Jordan

  9. #9
    i will get all the rest i need when im dead corkycat's Avatar
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    now you put it like that tommy yeah i agrea, i also think yamaha should sort this clutch problem out as a priority and i dont think im alone on that thaught

  10. #10
    David 1 FAST VE's Avatar
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    How about cryo freezing the clutch to harden it some? Would that make it last longer you think?

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