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Crank Bearings?

Discussion in 'XJ Technical Chat' started by Linker, Jun 7, 2018.

  1. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    Exactly that. The wedge exists because the oil is there. If the bearings were sealed so the oil could not escape, the oil wedge would still form (same as it does in zero-pressure or low-pressure oiling systems (total loss, drip, oiling cups like my lathe has, etc.). The downside of that is the oil would no longer be able to cool the crankshaft sufficiently. Bearings would spin. Much badness following shortly thereafter.

    Now if the engine were a two-stroke.....
     
  2. Minimutly

    Minimutly Active Member

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    Oiling cups - Myford ml7 kmoe?
     
  3. Franz

    Franz Active Member

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    Yes some engineering these bikes have, and some cost for replacement bearings that is why I will make sure I change the oil and filter regularly.
     
  4. Franz

    Franz Active Member

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    Like my MZ TS150 k-moe the first bike I had to get to work. Those Barum tyres were deadly in the wet. There was a cup fitted to the underside of the fuel tank cap for measuring the two stroke no seperate pump for the two stroke oil on that machine.
     
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  5. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    It's a Craftsman branded Altlas from the mid 50's. I'm saving up for new change gears (the ones I have are serviceable, but not for much longer.I have thought about just making them myself from bronze, but...so tedious), and a milling attachment (plenty good enough to suit my needs).
     
  6. Minimutly

    Minimutly Active Member

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    My ml7 has a milling attachment which I don't really need, but it was so cheap I couldn't pass it up. The Myford itself was a bargain, I allready had a Colchester Triumph, so the myford hasn't been used either - I really should sell it, but it doesn't eat anything.
     
  7. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    Mine dosen't see as much use as I'd like it to. Dad was a machinist, so I keep it around in part for sentemental reasons, and in part because I really do enjoy making my own parts when it makes sense for me to.
     
  8. cds1984

    cds1984 Active Member

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    I have 3 engines worth of shells.
    2 x 33F and 1 x 5G2, according to the parts listing these guys both use the same part numbers for the shells/colours.

    I went and purchased a sexy digital micrometer with a ball attachment and after zeroing out and doing a lot of testing in spots I ended up with this. (the last 2 on the page are odd balls in the engine I'm working on)
    [​IMG]
    from these,
    [​IMG]
    [​IMG]
    [​IMG]

    [​IMG]

    [​IMG]

    A whole lot of insanity it seems and the shells in the engine I am working on are basically all out of whack by the looks of things, but if I could just work out some sort of pattern... hmm hmm what do you think of these suppositions,

    MAIN BEARING OIL CLEARANCE 0.040 - 0.064mm (0.024mm)

    4H7-11416-01-00
    5G2-11418-00-00 BLUE - 0.064 (0.032/shell) - 1.500mm

    4H7-11416-11-00
    5G2-11418-10-00 BLACK - 0.058 (0.029/shell) - 1.477mm

    4H7-11416-21-00
    5G2-11418-20-00 BROWN - 0.052 (0.026/shell) - 1.474mm

    4H7-11416-31-00
    5G2-11418-30-00 GREEN - 0.046 (0.023/shell) - 1.471mm

    4H7-11416-41-00
    5G2-11418-40-00 YELLOW - 0.040 (0.020/shell) - 1.468mm


    Supposing that a BLUE is actually 1.500mm

    must be a way of working this out you'd think.
     
  9. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    From what I've read from people who have tried is that there is more than one manufacturer's part number for each color of bearing shell, and since those numbers were only used internally by the bearing producer, that makes it quite the puzzle to build a comprehensive list.
    Keep at it though. A pattern may emerge with enough measuring and recording to enable the system to be figured out.

    If you can't see the color bands on the sides of the shells, you can work out the what colors they are from the numbers on the case and the numbers on the crankshaft (if you remember what position the shells ame from, and which engine they are out of). That's what I did to find the correct shells for my case transplant a few years ago.

    One thing to keep in mind as you measure is that the actual thickness of the shell can vary across its surface, and the actual clearance may change from the calculated clearance when everything is torqued down in the cases. So when you go to put the engine together you really do have to confirm the clearances using plastiguage.
     
    Last edited: Jun 15, 2018 at 10:09 AM
  10. cds1984

    cds1984 Active Member

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    I think I have to buy a bunch of plastigauge.
    and...
    Pay attention to where the shells come from next time I end up with a scrap engine and strip it down.
     
  11. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    cds.......are those used shells that you are measuring? If so, it won't tell you much, and as k-moe states, those numbers on the back of the shells probably mean something, but what that meaning "is" may be unknown and unknowable.

    One version of the 900 service manual actually gives the CRANKSHAFT bearing shell measurements...these same shells are used on all XJ650, XJ700, XJ750, and all XJ900RK, RL, N/FN, and F engines:

    Blue: 1.5000 + 0.002 to + 0.006mm
    Black: 1.5000 - 0.002 to + 0.002mm
    Brown: 1.5000 - 0.002 to - 0.006mm
    Green: 1.5000 - 0.006 to - 0.010mm
    Yellow: 1.5000 - 0.010 to - 0.014mm


    CON-ROD bearing dimensions for all XJ650 (except Turbo) and XJ750 air-cooled engines:

    Blue: 1.5000 + 0.002 to + 0.006mm
    Black: 1.5000 - 0.002 to + 0.002mm
    Brown: 1.5000 - 0.002 to - 0.006mm
    Green: 1.5000 - 0.006 to - 0.010mm

    The con-rod #'s may be wrong, as they are duplicates of the crank numbers (excepting the yellow color "size", but, it is true that con-rod bearings never had a yellow "size", so it may be correct). ALSO.....these bearings may be the same for 700 air-cooled and 900 engines, but those rods have an oil-spray hole in their beam to lube the cylinder walls/piston skirts, and thus used a different upper rod bearing (with an oil hole), and may be the "same but different" bearing.
     
  12. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    Of all the innovative things that Yamaha did, the color system for bearings is the only one that they really messed up with.
     
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  13. cds1984

    cds1984 Active Member

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    Yes all used, I went back and forth and attempted to find the point that wasn't worn between the same numbered shells. Pretty frustrating and a good trainer on the use of a micrometer with this granularity. One of the sets is out of one of the original engines I had and was dropped on the reluctor side of the crank, damaging it... needless to say the crank journals look like new and the shells do too... damn shame, which is why I decided to find a pattern. The engine I'm working on, in contrast, seems to have had odd ball shells tossed in as the pattern(shell numbers and amounts) doesn't match the sequence when you do the calculations([reverse(case)] - [crank numbers]).
    Still all a bit of fun and I did find one shell that looked like it had colour on the side but... it was just the light haha.

    That is some good info! I will be using it pre-plastiguage. Good one.
    blue 1.506 - 1.502
    black 1.502 - 1.498
    brown 1.498 - 1.494
    green 1.494 - 1.490
    yellow 1.490 - 1.486

    ahah found the manual page [edit] xj900rk_service.pdf on the xjcd page number 7-7. Nice one.
     
    Last edited: Jun 15, 2018 at 10:26 PM

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