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Are XJ750 and XJ900 shaft drives interchangeable?

Discussion in 'Technical and Troubleshooting Torque' started by llewellyn, Mar 30, 2012.

  1. llewellyn

    llewellyn Member

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    Motorbike(s):
    1985 Yamaha XJ750P
    Hi Guys,

    The shaft drive of my XJ750 shat itself yesterday and I need to get a replacement. I have seen an XJ900 driveshaft/swingarm for fairly cheap locally, but I don't know If they are interchangeabler. Exact models are

    My bike: 1985 Yamaha Police Xj750 (based on 1983 XJ750 Seca)

    Other bike: 1983 Yamaha XJ900

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    Cheers in advance,

    Llewellyn
     
    #1
  2. ibast
    Tired

    ibast Shit Stirer Premium Member

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    Jebus, most people on this forum weren't even born in 85.

    can't say myself, but do be careful. From memory Yamaha tried to get all high tech with the xj 750, so the motor is different from the 900.

    Maybe take some key measurements of yours and ask the seller to do the same.
     
    #2
  3. llewellyn

    llewellyn Member

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    Cheers Ibast. That was going to be my plan if I can't get any specific information, but I was worried about the possibility of the two swingarm/shaft drives having the same external dimensions but different internal components.
     
    #3
  4. PatB

    PatB Premium Member

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    I can see the 900 having taller gearing than the 750, which is not necessarily a deal breaker.

    Spline patterns on the ends of the drive shaft would be the most likely sticking point as far as internal differences are concerned. Shouldn't be too hard to pick visually if you can take your broken bits along as a comparison.
     
    #4
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  5. llewellyn

    llewellyn Member

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    The problem with my shaft is that something has broken on one of the joints in the middle of the shaft and caused a bit of havoc in there (i was fishing metal shavings out of the rubber boot connecting the shaft to the engine). If the gearing is the only difference, I can probably make a bitsa, using the parts from my diff with the shaft parts from the 900 (if that is the only difference. I will try remove the shaft from my bike tonight and I will take it with me when I go part shopping tomorrow.
     
    #5
  6. MV
    Amused

    MV Throttle Monkey Vendor

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    Jump on part shark.com, find part number of the driveshaft for your bike, see if it correlates to the same part for the 900.

    It's an american website, so model names etc might be a little different.

    Even if the part number don't match, they may still be interchangeable, but you'll probably need to get them next to each other to work that out.

    Good luck!
     
    #6
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  7. llewellyn

    llewellyn Member

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    Hey MV,

    Thanks (I suppose its nods now) for the advice. The site that you listed didn't have the part but it gave me the idea to try and find the part numbers for the two drive shafts and compare them. Unfortunately they have different part numbers, but at least this saved me the trip to look at a driveshaft that wouldn't fit.
     
    #7
  8. MV
    Amused

    MV Throttle Monkey Vendor

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    I got your nod, I'm glad it was helpful. :)

    Even if the part numbers are different, they could still still be interchangable, some Yamaha part numbers are coded with the bike model as well, you'd need to the two parts next to each other to make sure.
     
    #8
  9. GreyBM

    GreyBM Premium Member

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    Someone like VicWreck in Heidelberg Vic may have a second hand shaft and may also be able to answer your question.
     
    #9
  10. llewellyn

    llewellyn Member

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    Cheers GreyBM,

    At the moment the plan of attack is:

    1) When the kids fall asleep tonight I will go out into the shed and remove the swingarm/shaft-drive and check exactly what components from the shaft drive are stuffed

    2) I will probably try to check out a guy who is selling a complete XJ900 swingarm/diff assembly for $150. I will take mine with me and compare it. I know the part numbers between the two are different, but as MV said, they may be interchangeable.

    3)If that doesn't work I will hit up the local (Perth) wreckers. If that fails I will start checking out interstate wreckers/ebay.
     
    #10
  11. GreyBM

    GreyBM Premium Member

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    I am fairly sure VicWreck does interstate. And they have an amazing (albeit sad due to the crashes that have created them.) array of stuff.
     
    #11
  12. Speak for yourself dude. I had just bought my first brand new bike. A 1984 Yamaha DT 125 LC stroker traily. And I don't consider myself old at all :)
     
    #12
  13. llewellyn

    llewellyn Member

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    OK, thread update.... I removed the smingarm and shaft drive and I found that the problem was that the universal joint at the engine side of the shaft drive had carked it. I have sourced one from a local wreckers for $50 (cheers GreyBM for recommending those Heidelberg wreckers, but the said they don't keep parts for bikes this old) and I will install it either tonight or tomorrow night. Before I do it though, I have one question for you guys....

    The manual doesn't mention lubricating the universal joint at all. I was thinking that it would be wise to give it a good coating with a general purpose (lithium?) grease before I install it. Does this sound reasonable? How would you lubricate the joint?

    Thanks in advance,

    Llewellyn
     
    #13
  14. PatB

    PatB Premium Member

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    I don't know what Yamaha fit, but most UJs these days are sealed for life, in that the lube they require is sealed in when they're assembled. Once upon a time, UJs had a grease nipple (or a plug where one could be fitted) on the spider so fresh grease could be pumped in without dismantling but I haven't seen one of these in a couple of decades.

    The only way I know to effectively relubricate a modern UJ is to press it all apart, clean up the caps, rollers and spider, then reassemble with new grease. Not particularly complex (although you need a press or a big vice and suitable tubes and slugs to allow you to press out the caps. Sockets do the job) but a bit time consuming.


    If there are any splined joints, you need a grease that will deal with high contact pressures. You don't need much, but you do need the right stuff. In WA, if I wasn't dealing with splines frequently (which I don't) I'd go to Munich Motorcycles in Myaree who'll sell you a little pot of the good stuff (for about 10x what they paid for it I suspect) which they stock for BMW K100 final drive splines. You only need a smear so one pot should last you several years of normal use.
     
    #14
  15. llewellyn

    llewellyn Member

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    Cheers Pat. The way the joint is set up is that it bolts onto another shaft at the engine end of the joint, and there is a cavity at the wheel end of the joint, into which a spline on the end of the driveshaft fits (I assume this is what you described as a splined joint, I am not great with technical terms). I suppose I will have to track down some of this grease when I pick up the joint.

    Thanks for your advice. I am generally pretty good at the taking things apart and putting them back together side of mechanics, but I struggle with stuff like what lubricant to use and when, when the info isn't given in the manual.
     
    #15

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