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Thread: Riddle me this: chipped head gasket surface

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    Member wheel_of_steell's Avatar
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    Riddle me this: chipped head gasket surface

    So after a few thousand kays of ownership, (got it at 8k, now has 12k) the cb125e has developed a small oil leak at the base of the head under the exhaust port.

    No biggie, I assume the head gasket is bad and get in there to replace it. At the source of the leak, I discover this tiny, tiny little chip in the sealing face of the head. What could cause this? As far as I'm aware, this engine has never been apart. It's been looked after with regular oil changes and frequent usage in all conditions. I have filled the hole with a tiny amount of RTV and flattened the surface with a library card. Hopefully between that and a new gasket the leak is fixed. But I feel uneasy repairing something without addressing the actual source of the problem.



    Is this operator error? Manufacturing flaw? Unlucky stone chip? Someone else has already been in here?
    Quote Originally Posted by devolved
    I just crashed into a schoolbus full of kiddies, killed them all, raped them, set them on fire and now I'm pissing on their charred remains.

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    Member Water pig's Avatar
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    Looks like it could have been some swarf from manufacturing in Thailand

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    either that or air bubble in the casting
    Quote Originally Posted by Paraletic View Post
    little end bearing. best describes as the sound of 'A little black man with a hammer in your engine'. big end sounds like a bigger black man...

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    Member GsxInShed's Avatar
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    Pry mark from screwdriver to lift the head..What does the corresponding gasket face look like..
    " Imagination is the seed of life..."

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    Member Water pig's Avatar
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    Quote Originally Posted by GsxInShed View Post
    Pry mark from screwdriver to lift the head..What does the corresponding gasket face look like..
    I agree that itís what it looks like, but Iím giving OP benefit of the doubt as he would be unlikely to post a picture of his own fuck up, unless It was funny.

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    It's only funny if it was his 'fukup'

    If the cunts put it together like that... it's a whole other story...

    A head that size.. 0.00 mm tolerance on flat...over the whole head...

    mass production something something ...

    Bubble would leave a divot ..after machining and Joe Bonus-Time would've chucked it to the rework pile...and had it recycled as a neck piece for the fuktard that did final head surface check...Imho

    EDIT... again..... Did you happen to get the bores in a pic???? Or the rest of the barrel surface??? if a foreign body it will be/was still there when you pulled....

    Oh and say wah..???? metal putty ...'nead it' or similar would be the only form of repair......
    " Imagination is the seed of life..."

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    Member Slug_BM's Avatar
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    Silly question. If it's an oil leak, wouldn't that be from the base gasket not the head gasket? I'm not certain if you'd see an oil leak from the head gasket unless it was accompanied by low compression and exhaust gases escaping. Hopefully that pit is far enough away from the combustion chamber as not to pose a problem. Did you double check the base of the barrel?
    It's all fun until someone loses a nut.

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    Slug_BM is on the money.

    There aren't any oil galleries near that tiny mark. Or oil. Why do you think the oil is coming from there?

    If the mark left no raised edges then it's not going to concern the sealing of the gasket. Leave it be. Don't put RTV on it and leave it to dry. If the head gasket specifies that it needs sealant applied then that's all you should do.

    And a "library card"? Where in the 90s did you find one of those?
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    Member wheel_of_steell's Avatar
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    Quote Originally Posted by GsxInShed View Post
    Pry mark from screwdriver to lift the head..What does the corresponding gasket face look like..
    Quote Originally Posted by Water pig View Post
    I agree that itís what it looks like, but Iím giving OP benefit of the doubt as he would be unlikely to post a picture of his own fuck up, unless It was funny.
    There is a slight witness mark on the gasket face, but it's slight. No real sign of like, gasses being forced out a passageway or anything like that.
    (Also thank you water pig - head was liberated with a rubber mallet - I wouldn't be screwdrivering up a leaking head to fix damage that would have been caused by screwdrivering up the head. Or if I did, I wouldn't be posting about it)

    Quote Originally Posted by Slug_BM View Post
    Silly question. If it's an oil leak, wouldn't that be from the base gasket not the head gasket? I'm not certain if you'd see an oil leak from the head gasket unless it was accompanied by low compression and exhaust gases escaping. Hopefully that pit is far enough away from the combustion chamber as not to pose a problem. Did you double check the base of the barrel?
    Good point, normally I'd agree, but the source of the oil seems to be the bottom left thru-hole where the head bolt passes through everything.

    I guess oil circulates up and down some of those channels? No sign of combustion gasses blowing out of the gasket and no other symptoms of an exhaust leak, thankfully. Also the black, oily muck was definitely coming from the head/barrel seam and nowhere else.

    Quote Originally Posted by Loud View Post
    And a "library card"? Where in the 90s did you find one of those?
    Where else can you find a heart warming mix of free workshop manuals and sleeping homeless people?
    Last edited by wheel_of_steell; 18-04-2018 at 08:17 PM. Reason: forgot pic
    Quote Originally Posted by devolved
    I just crashed into a schoolbus full of kiddies, killed them all, raped them, set them on fire and now I'm pissing on their charred remains.

  10. #10
    Member GsxInShed's Avatar
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    Is the head flat? 'cause you would've checked that before you put it back on...

    Yes oil does feed the valve train through that hole...in some cases...it's only a return ...yours has a metal feed line to the rocker cover??? How is the internal metal areas in the valve/tappet region..?

    Oil pressure is..? Hi..? Low? see spec for answer.. I suspect plain brgs for the crank...oil pressure would be 35-65 psi at 3000 rpm.... Roller crank...5-10 psi same...rpm

    Were the head bolts tight... ( if not overheat is the answer...) don't ask me the question..

    Umm google says... this little motor doesn't have an oil filter... I hope she's wrong.....you would at least expect it to have a magnetic sump plug...

    What does the spark plug look like....? any more pics... ( pardon me for being nosy..)
    Last edited by GsxInShed; 18-04-2018 at 08:43 PM.
    " Imagination is the seed of life..."

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