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Dumped oil through crankcase breather

Discussion in 'Technical and Troubleshooting Torque' started by mattb, Feb 26, 2011.

  1. There are plenty of threads about this scattered across the net but I thought I'd write up my particular experience today and get some opinions just the same. Today Quarterterwit and I travelled for about 20 minutes down the freeway (from the city to Sprinvale road exit) at just short of 100kph (4,500rpm) when suddenly I looked back to see white smoke going every where. The bike - SR500 - was running strong, so I left it idling while I looked for the possible cause. No smoke out of the exhaust, just smoke coming off the exhaust - it, and everything at the rear right side of the bike, was covered in oil. Side covers off, and it seems pretty clear than it was dumped out of the crankcase breather, which I have modded as a clear tube running 30cm back under the seat to a foam air filter. Now, why might this have happened? I had over-filled the oil a bit, but often do so (it likes to drink a little oil) and never has the bike done this. Compression is great. Why would it dump all this oil at once (about a cup's worth, perhaps)?

    We rode it straight home via the same route and there were no further problems. A tiny wave of oil was working its way up the pipe when i held the throttle open at 4000rpm, but not in anything like the volume that must have been thrown at once up the tube, or perhaps which slowly gathered and then went splat out fo the breather. I figure I'll go for a couple of freeway runs this week before I take teh bike on a proper ride again. I don't like oil on my tyre.

    Hope this is coherent - I'm on an overnight shift.

  2. You put a little more oil in than you normally do. Pretty sure the SR runs dry sump/oil in the frame. The anti bleed back valve may be leaking slowly overnight and filling the cankcases. The scavange pump may not be able to cope for a while and so she pumps it out the breather. Just a thought.