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Thread: Small amounts of metal in oil

  1. #1
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    29th October 2018 - 12:06
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    Small amounts of metal in oil

    Hi, I have a couple of older bikes (an RD250 and RD400) that both consistently have small amounts of metal in the oil. There are no large chunks or flakes, it's more like a fine metallic dust. If you pour the oil, it appears reasonably clear and you can't see the metal.

    Both bikes have magnetic drain plugs, and usually there is just black sludge on the magnet, which leads me to think maybe the metallic stuff is aluminium.

    The 250 has covered 40,000km since its last full rebuild (yikes), so I've always assumed the metal is just a result of general wear and tear through the gearbox. The 400 has just had a rebuild, but I didn't replace any gearbox components as they seemed OK upon inspection. But I wasn't really expecting any metal to be present in the oil after 3-400km of riding.

    This leads me to the question of: how much (if any) metal is considered "normal" to see when draining motorcycle gearbox oil?

  2. #2
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    13th June 2010 - 17:47
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    Visible metal particles in 2T gearbox oil isn't normal. I'd suspect you've gone through the hardening somewhere in those two boxes.
    Given their age, it isn't too surprising.
    Could be a gear or two - or a thrust washer. At some point you'll either have something break or start making noise.
    I probably wouldn't worry too much about it till then...
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  3. #3
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    29th October 2018 - 12:06
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    Quote Originally Posted by Grumph View Post
    Visible metal particles in 2T gearbox oil isn't normal. I'd suspect you've gone through the hardening somewhere in those two boxes.
    Given their age, it isn't too surprising.
    Could be a gear or two - or a thrust washer. At some point you'll either have something break or start making noise.
    I probably wouldn't worry too much about it till then...
    I suppose it is hardly surprising. I guess I'll just have to keep a clone eye on things. I have a spare gearbox with good gears, but I obviously don't want to grenade anything in the meantime. Will pull the clutch cover this weekend and have a look-see. The 250 will be an interesting teardown, curious to see what it's like inside. It's very very close to going around the clock, and I was trying to get it there, but it's gonna need a rebuild before that happens haha.

  4. #4
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    25th March 2004 - 17:22
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    Those earlier gearbox are a bit prone as I understand but the good news is they beefed up the YPVS so it can seemingly handle 100hp.

    Well it's good news for me, so that's a thing.

    There isn't really anything ally that can wear unless you are rubbing something against the clutch basket.
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  5. #5
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    12th February 2004 - 10:29
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    On the rebuilt one a hardened thrust washer missing off the end of a shaft might let a cog meet alloy

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