Symptoms of cracked head?

Discussion in '2-Stroke Engines' started by mattysids, Oct 28, 2009.

  1. mattysids

    mattysids Member

    Here are some pictures of the head of my engine

    -There is burnt oil on the side and top of the cooling fins near the plug but the head gasket looks perfect

    -My bike is incredibly hard to start and will only fire when engaging the clutch down a huge hill

    -Once started it will continue to run as long as i keep engine revs high, but puts out at a very high idle

    -Originally guessed electrical problem but ruled it out because it runs fine once it starts

    -The failure to fire at low RPM's suggests to me that compression is failing

    -The bike is much easier to push forward with clutch engaged than it used to be

    Any thoughts?

  2. mattysids

    mattysids Member

    Here are the pictures

    Attached Files:

  3. fetor56

    fetor56 Guest

    Tighten your head bolts to spec(10-12 ft/lb) & in an X pattern.
  4. mattysids

    mattysids Member

    already tried that

    still no use

    once again the oil is NOT coming from the seal between the head and the jug
    Last edited: Oct 28, 2009
  5. Al.Fisherman

    Al.Fisherman Active Member

    Had the same oil seepage until I got rid of that trash Chinese plug and installed a NGK. As far as the compression....test it.
  6. Pablo

    Pablo Motored Bikes Sponsor

    Spark plug is a good place to start.

    I would get a good plug, new head gasket (and me being anal, new studs, but not required, but new NUTS* for sure), clean the heck out of everything and inspect for cracks, if none spotted, reassemble and re-torque.

    *The acorn nuts could be bottoming.....
  7. motorpsycho

    motorpsycho Active Member

    I would go to the ngk plug. The gasket on the stock plugs are junk, and they will not seal the spark plug hole completely. The spark plug gasket will allow oil to be blown out of it. My 50 c.c was doing the exact same thing until i went to the ngk plug.
    But it looks like you already have the ngk plug. The gasket on the plug could be installed upside down, which would allow oil to be blown out. The spark plug gasket is "stepped" and the smaller side of the gasket should be against the spark plug hole. The spark plug gaskets actually crush to make a good seal after you put a new plug in, so it's is possible that the gasket will not seal anymore from constant removal / installation of the spark plug. When the gasket crushes, it conforms to any irregularities that the spark plug hole may have. If the gasket position is changed, it may not be sealing around the irregularities that the spark plug hole may have. This is a long shot, but it is possible.
    Last edited: Oct 29, 2009
  8. Al.Fisherman

    Al.Fisherman Active Member

    You got that right... The acorn nuts need not be used at all. I use nylon self locking nuts along with all new studs. I have checked the torque specs and I was only able to tighten them up one time...after my first ride after the mod...never since in the 300 miles I've put on it.

    Insert plug, remove head, secure head in a position that the head gasket surface is up. Pour gas into the head cavity and watch.
    Last edited: Oct 31, 2009
  9. juliman

    juliman Member

    could be oil from exhaust as for the other stuff i dont know?
  10. AussieSteve

    AussieSteve Active Member

    This doesn't relate to your starting problem, but the oil on your head is in the same places as on mine. On my bike, this is caused by the fuel tap weeping and occasionally dripping onto the head. When the fuel evaporates, the oil remains.
    Regarding starting, as others have suggested, first try a new (NGK) plug.
    You mentioned that the compression seems low. How old is your engine?

    ... Steve