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oiler hole ??? in Sprocket-Side Case Cover

Discussion in 'The Garage' started by DogBunny, Aug 29, 2018.

  1. DogBunny

    DogBunny Motorcychologist Top Contributor

    s-l1600.jpg
    I have three left-side case covers with the added hole like in the picture above. I think the theory is that previous owners added the hole and routed the crankcase breather to it so that engine blow-by would lubricate the chain. However, I measured, and the holes in all three of my covers are in exactly the same spot and are the same diameter, indicating that these were mass-produced this way. You also see a lot of these covers with holes in them on eBay. Is it possible that some XS650 sprocket covers left the factory with these holes? Any thoughts?
     
    Jake650 and gggGary like this.
  2. 5twins

    5twins XS650 Guru Top Contributor

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    Yes, some early covers came that way. The factory routed the oil breather line through there before pollution mandates made them do otherwise. I think it was done up until 1975. 1976 got the hoses run into the airboxes.
     
  3. DogBunny

    DogBunny Motorcychologist Top Contributor

    Thanks for that explanation. It's a confusing situation. I have never seen that hole shown on a case covers parts drawing. Also, all of the early crankcase breathers had two outlet pipes -- why would you employ two outlets, only to have them wind up in a single case cover hole. I thought ALL breathers were run into airboxes, but I could be wrong about that.
    Those holes do appear to be factory-made, but it's like some case covers got the hole, and some didn't, even within the same year model.
    One more thing -- of my three covers that have the hole, one is an early square-corner cover, and the other two are rounded-corner covers. Weird.
     
    Paul Sutton likes this.
  4. 5twins

    5twins XS650 Guru Top Contributor

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    Although the early breather box had 2 outlets, for a time Yamaha capped one and only ran one hose. I'm thinking those could be the years with the hole in the cover.
     
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  5. DogBunny

    DogBunny Motorcychologist Top Contributor

    Interesting, I never knew that. Thanks for the info.
     
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  6. 5twins

    5twins XS650 Guru Top Contributor

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    Studying actual parts manuals (not on-line diagrams), 1975 seems to be the only year showing the single hose and plugged off other outlet. Maybe it was a one year only thing?
     
    DogBunny, Paul Sutton and gggGary like this.
  7. delagem

    delagem XS650 Addict

    My gut reaction here is that the primary product of blowby is moisture. Wouldn't this mostly just vent damp condensation and acidic droplets of water onto your chain?
     
    DogBunny and gggGary like this.
  8. 5twins

    5twins XS650 Guru Top Contributor

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    In the case of these 650 motors, I think there's lots of oil mist mixed in there with it, so much so that Yamaha got complaints about it on the first few models. Their big "fix" was to lower the oil level in the crankcase by 500cc or so. That lowered the oil level about 10mm I think. Along with that, they started reworking the breather configuration. First attempt was plugging one outlet and running just the other one. Second attempt had them go back to using both outlets but with rubber reducer plugs stuck in them. These necked down the outlet holes to about 1/8". Final change was a whole new breather box with only one outlet and having the reduced hole size built right into it .....

    [​IMG]
     
    JAX71224, Jake650, DogBunny and 4 others like this.
  9. DogBunny

    DogBunny Motorcychologist Top Contributor

    So far, I like this explanation. If you have your parts manual handy and it's not too much trouble, what is the part number for the cover with the hole? My references all show 1975 to be 584-15411-00-00 which is the same as 1976-1983.
     
    gggGary likes this.
  10. 5twins

    5twins XS650 Guru Top Contributor

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    As you mentioned, no hole is shown in any of the drawings, but there are a couple other parts numbers listed. They are 306-15411-04 and 306-15411-01. But those listings also seem confusing. A 1974 TX650A manual lists the "-01" number but some combo '70-'73 and '74-'76 manuals list the "-04" number. I suppose one could be the cover with the hole in it, the other with no hole, but I don't know how we could ever find out.

    All the pics I've been looking at only show the hole and single hose through it on the '75 model.
     
    DogBunny and gggGary like this.
  11. willis

    willis xsive compulsive disorder XS650.com Supporter Top Contributor

    My 75 is set up that way. Dual outlet breather with one side plugged and the other vented to the hole in the cover above the sprocket. I’ve been searching through my XSB service manual but cannot find any mention of the breather. As a matter of fact some pictures are of older models with the old style side covers.

    6166317A-D315-493F-AE48-D7BA38EC7CF6.jpeg 50DD64DD-898F-40A1-9613-0BF54182AB03.jpeg
     
    Jake650, DogBunny, gggGary and 2 others like this.
  12. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    Never noticed or seen that breather hole on the side-cover. 75 year was a change at the corner of the cover, (obviously the engine case as well), front and right over the clutch push-rod area. Went from a square corner to a round. ......74 and earlier on the right. ............
    P1110358.JPG

    When did the numbers for the gear selector gear get stamped on the engine side-cover. I thought it was around 74. Looking at some 73TX pics and i can't see it stamped on the case but the 74 definatly has..........This might account for a change or discrepancy in the side-cover part # prier to 75
     
  13. DogBunny

    DogBunny Motorcychologist Top Contributor

    Thanks Skull, willis and 5twins. I think we made some progress, but as 5twins said, I don't think we'll ever nail this down completely.
    cases.jpg
    Here are the covers Skull just showed, but with factory breather holes. The square-corner cover on the left does have the gear selector numbers cast in. I never noticed that the earliest covers didn't have that, good to know.
    I'm going to say that my square-corner cover with breather hole above is a 1974. My best guess now is that the breather/oiler hole started some time in 74 and lasted through 75. It would be great if someone else with a square-corner cover and oiler hole would chime in.
     
    Paul Sutton and gggGary like this.
  14. 5twins

    5twins XS650 Guru Top Contributor

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    Yes, it very well could have been a mid year change. That happened before on these bikes (elimination of the electric rear brake shoe wear switch in mid '77).

    Willis, if you ever get the chance, a pic of the plugged breather side would be nice.
     
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  15. willis

    willis xsive compulsive disorder XS650.com Supporter Top Contributor

    As requested... note that it is totally capped off, not just a restriction plug.

    7BC74FC7-13FC-426D-B27C-AF18B6E981DB.jpeg
     
  16. bluesman650

    bluesman650 XS650 Enthusiast

    Well, I have a 75 that I bought new. It has square corner and no breather hole. I also have a 75 that I bought as a parts bike a few years ago. It has the hole and rounded corner. For years I just thought it was a mod by a PO.
     
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  17. DogBunny

    DogBunny Motorcychologist Top Contributor

    willis, thank you for the interesting plugged breather pic.
    Hmmm, a square-corner 1975 confuses things. Maybe a very early 1975? More reports from 1975 owners would help, as well as VINs, so maybe we can figure out when changes were made. bluesman and willis, would you mind sharing your VINs?
    As I shared in a related thread, I have a round-corner 1975 engine with VIN 447-115238. 1975 production started with 447-100101, so I think mine's late 1975.
     
  18. DogBunny

    DogBunny Motorcychologist Top Contributor

    Okay, so I looked at 1975 cases for sale on eBay. Here's what I found, along with links to the listings in case anyone wants to verify:
    447-102493 Square https://www.ebay.com/itm/351981342560
    447-103XXX Square bluesman650
    447-103655 Square https://www.ebay.com/itm/332051545669
    447-103869 Square https://www.ebay.com/itm/231516753712
    447-109574 Square YamadudeXS650C
    447-111479 Round willis
    447-115238 Round DogBunny
    447-119373 Round https://www.ebay.com/itm/381733117805
    447-120562 Round https://www.ebay.com/itm/282309681057
    447-1211?? Round https://www.ebay.com/itm/392092299465
    447-127044 Round bluesman650

    Not a huge amount of data, but it seems to definitively show that the change from square to round-corner cases happened mid-way through 1975 production.
    EDIT: inserted willis' into the list, and will add any other contributions.
     
    Last edited: Sep 1, 2018
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  19. willis

    willis xsive compulsive disorder XS650.com Supporter Top Contributor

    447-xxx479
     
    Last edited: Aug 2, 2019
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  20. DogBunny

    DogBunny Motorcychologist Top Contributor

    Thanks willis.
    More evidence and more mystery:

    DSC03780.jpg
    So, I never noticed this before, but it turns out my 447-115238 1975 round-corner has the plugged breather.

    DSC03779.jpg
    Then I found this engine in my shed. Another plugged breather. But what's weird about this one is the VIN:

    DSC03778.jpg
    365-020644. I challenge anyone to show me a model chart that shows the 365 prefix.
    It is a decompression model. It has a square-corner. The plugged breather indicates that the left case cover must have had an oiler hole.
    I'm calling this a 1974 model.
    Anyways, further evidence that oiler holes precede 1975.
     

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