Black gunk from a 2 stroke motorbike engine exhaust?

Question by alex p: Black gunk from a 2 stroke motorbike engine exhaust?
Ive got a 2 stroke racing motorbike, but recently ive noticed some black goo dripping from my exhaust. Only a little bit mind you, but was wondering why. I understand the petrol oil mix is gonna make a lot of smoke, but blank gunk?

Best answer:

Answer by Zac V
probably just build up from the exaust.

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8 Comments
  1. Reply
    somwone145 May 11, 2013 at 2:39 pm

    the smoke probably built up in your exhaust system

    you might want to clean that out and check your oil gas mixture ratio to see if they’re correct, you might be adding too much oil

  2. Reply
    randy c May 11, 2013 at 3:01 pm

    you’re using to much oil in the mix

  3. Reply
    Mr X May 11, 2013 at 3:51 pm

    It’s normal for two-strokes to produce some oil,if it was all burnt then it wouldn’t lube the engine.The reason you see it dripping from exhaust manifold is that you have a leak.It would normally run into exhaust,where,over time it would mostly dissipate with heat with a small amount collecting on exhaust.It would also help to make sure tou have the correct oil/fuel ratio.

  4. Reply
    guardrailjim May 11, 2013 at 4:47 pm

    When was the last time you rebuilt the top end? (cylinder, piston & rings).
    It might be time, if it’s been awhile.
    When a 2 stroke loses compression, the oil in the pre-mix doesn’t get fully burned and oil builds up in the exhaust.
    Eventualy dripping “black gunk”.

  5. Reply
    barry m May 11, 2013 at 5:19 pm

    That means it is time for you to re-pack the silencer.

  6. Reply
    idahoatvryder May 11, 2013 at 5:30 pm

    Try Amsoil Dominator oil you mix it 50:1 also it is normal to have some build up. In a 2 stroke engine oil and gas are mixed you allready know that. What happens when you shut it off there is gas and oil in the bottom of the crankshaft this is normal. after it sits for a while the gas evaporates and there is oil left. so the next time you start it you get extra oil to burn on start up. some of that oil will simple not burn but will get pushed into your exhaust system. and it also picks up any carbon residue that is left in the exhaust pipe so thats why it’s black.
    It also could be jetted rich

  7. Reply
    Darren R May 11, 2013 at 6:11 pm

    its no problem it occurs in all 2-strokes its just residue from the petrol and oil mix dont worry its fine.

  8. Reply
    tobykaly May 11, 2013 at 6:49 pm

    its norm you should be able to take out baffles and burn off excess oil and carbon

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