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Brown Oily "stuff" from airbox drain?

Discussion in 'Technical and Troubleshooting Torque' started by Doggy, Oct 13, 2005.

  1. Ok someone mentioned a brownish oily substance coming out of the airbox drain a while ago? Well I went for a big ride on the w/e and have noticed a few spots on the exhaust behind the aforementioned drain. I checked the drain and there is a very small (couple of drops) ammount of a brownish oily sort of liquid at the bottom of the drain. It's only a very small ammount but the spots cause discolouring on the exhaust and don't look very good. Also I'm just curious to know what it is.

    Bike is a 2003 GS500 very good nick
    12,000km on the clock and is ridden daily (shortish distance)
    not using any oil, just serviced (2000km ago) and running fine as far as I can tell, no fuel issues or anything just the usual soft forks.


  2. Not sure if this is the same situation, but Cheng's Across had oil up in the airbox, quite a pool of it.

    Speaking to Pete the Pom, he said it was the result of an oil overfilling... In this case to the tune of a litre and a half - and the extra oil was being sucked through into the airbox. Apparently reasonably harmless, although it's not good to have too much oil in there for any length of time.

    How's your oil level? Any chance you've overfilled?
  3. Not unless it was a long time ago (maybe before I bought it) but I regularly check the fluids and alls ok there. I get it serviced at the local dealer and I check fluids when I get it home just to make sure. But no I don't think it's been overfilled lately. It also only seems to appear after long rides. My short commute to work does not seem to develop it.

  4. This is simply 'oil blow by'.
    It is when oil is 'splashed' up during hard riding/ driving and it gets sucked up through the crankcase breather (which often ends up at the airbox).
    An oil catch can fixes this problem (can prove to be difficult to fit on a bike though!).
    I kept getting oil in my intercooler on my car and a catch can fixed it right away.
    In major cases, oil going through the intake can also reduce the octane level during combustion, which can cause detonation.
    Daz. :wink:
  5. Ahh it's a "you just flogged her" tell tale. No worries then.

    Thanks to those who replied...

  6. All engines that are used for commuting will to some degree end up with condensed fuel and water entering the oil from the cylinder walls, it happens while the engines running rich (coldstart).

    When you take it for a good long blatt, the engine and oil get nice and hot and the water/fuel sludge evaporates or gets burnt out. it makes its may into the airbox via the "positive crankcase ventilation" system

    A good technical reason why all bike owners should go for a nice ride every sunny weekend :wink:

    Pity they put the drain over the exhaust tho.

  7. Yeah the drains about 5 " infront of where the exhaust starts to make it's way to the right side. It's in a perfect position to splatter the exhaust at high speeds. There is also two other drains which come out there as well (fuel filler drain & Carb o'flow).

    Thanks again...
  8. Hi Doggy,
    On one on the bikes I had, a mechanic who tuned it suggested this,
    In the hose that goes from you engine to air filter box,
    Insert a disposable fuel filter (select a size to suit the space you have)
    It will take out the water and any oil vapour, and once it is dirty replace it,
    You must mount if horizontaly, to stop any moisture flowing back into your engine,
    Worked a treat on my old Z650, stopped the crap from ending up in the airbox, and the filter was $2.95 (from supercheap or like store) as opposed to the thirty something dollars for the replacement airfilter.
    If you cant insert in the line to your air box, could always put in the output line to stop it from dropping onto your exhaust.
  9. Thats a good idea, I'll certainly check that one out.
  10. Not sure this is a good idea. The breather has several functions, one of which is to remove water vapour (condensation) from the crankcase. Putting a filter in-line will change the volume of air in the system, due to increased pressure caused by restriction (by Boyles law, PxV=C) and could increase condensation, and therefore corrosion, in the crankcase. As is usually the case, if such a simple 'fix' is not part of the original design, there is usually a good reason why.
  11. alternatively, if it has an oiled air filter, you may have just overdone it a little