Changed head gasket

Discussion in '2-Stroke Engines' started by Rezin, Aug 5, 2014.

  1. Rezin

    Rezin New Member

    Changed head gasket on my motor, but it looks like it is cut wrong cuz the in side that go's around the in side piston is in the piston chamber. I looks like the piston will hit it on the up stroke. Is this right?
     

  2. jaguar

    jaguar Well-Known Member

    no that's not right. get another gasket from a different source or trim away at the gasket you have.
    also plane the head and cylinder top with sandpaper and glass while you're at it.
     
  3. Rezin

    Rezin New Member

    Thanks man, for the info. I'll do all that this after noon. Did not want to put it back together and then have to tear it down to do it all again. I'll post pics of it . Thanks again!!!!
     
  4. Fabian

    Fabian Well-Known Member

    Sounds like you have the wrong gasket.
     
  5. Rezin

    Rezin New Member

    Had no time to put the head on so I gave it to my freind to do .I think he messed up the head. He cut the gasket to fit around the raised ring on head and he also grinned the in side edge of the raised ring off. Now the bike will not start for anything. He f up the seal seat on the head dident he....
     
  6. butre

    butre Well-Known Member

    just plane your head and get a new gasket
     
  7. Rezin

    Rezin New Member

    Look at this crap

    Look at this... image.jpg image.jpg
     
  8. butre

    butre Well-Known Member

    I can't think of any reason why he'd do that. just plane your head and get a gasket that fits instead of hacking up the wrong one
     
  9. jaguar

    jaguar Well-Known Member

    he didn't mess up the sealing surface so don't worry about the abrasions. they won't affect it.
    click on my signature link to read about planing the head in my "increasing cylinder compression" section.
    very essential because the stock head is not flat (or the cylinder top)
     
  10. jaguar

    jaguar Well-Known Member

    also the best head gasket is one you make yourself using an exacto knife (available in hobby stores) and gasket material from the auto parts store. fiber contours to minor head variations.
    but the head varies more than "minor" so first plane it.
    In a tight spot I have also made one from a cereal box. It worked for about a month. actually worked real good being fiber. the heat finally burned it. but that may never happen with a stock setup because the engine compression is low.
     
  11. butre

    butre Well-Known Member

    I got mine so close to perfect that it would run without a gasket, and then put a gasket in to drop the compression a little bit.
     
  12. jaguar

    jaguar Well-Known Member

    you can do that although not advised. the head warps a bit since the exhaust side gets hotter than the intake side. I tried that and knew from the oil seepage to the outer area of the head mating surface that it wasn't sealing perfectly. It might be somewhat workable for a while though with a good sealant like copper coat.
     
  13. Fabian

    Fabian Well-Known Member

    Nothing like a good billet cylinder head to stop the top end oil leaks, not to mention a properly designed combustion chamber.
     
  14. Rezin

    Rezin New Member

    Re- planed the head and installed. Will not start for anything I try, getting fuel, getting spark although the spark is very minimal. Can having to little compretion be the prob or my cdi craped out?
     
  15. Fabian

    Fabian Well-Known Member

    You need to understand that the cylinder head has a machined lip just outside of the combustion chamber area, which is designed to bite into the head gasket. When you plane or sand the cylinder head smooth, the lip is removed and makes it harder for the cylinder head to create a seal between the underside of the cylinder head face and the head gasket.

    Planing or sanding the cylinder head can make a problem worse or create a problem that wasn't there in the first place.
    Considering that the cylinder head gasket is made from very soft aluminium (designed to squash and conform to the irregularities of the cylinder and the cylinder head), you will need to regularly re-tighten the head stud nuts to ensure correct tension is maintained on the cylinder head.

    I check and (if necessary) re-tighten the head stud nuts every 500 kilometers (300 miles).
     
  16. HeadSmess

    HeadSmess Well-Known Member

    using any fibrous gasket material, cardboard especially...is just plain STUPID. only "metal reinforced" fibrous gaskets can withstand the pressure.

    ive tried teflon tape twisted up into "string" as an experiment. if it works for high pressure flange joints dealing with steam at 1600psi... go figure :p in fact, ptfe sealing tape is rated at 140 bar or MORE!...which is well over 2000psi ;) fiddly to ensure its in the right spot though if used as a head gasket :( temperature? if the heads getting over 250C theres problems anyway ;)

    http://www.alliancesealing.com.au/?page_id=446
    http://www.gore.com/en_xx/products/sealants/gaskets/GORE_joint_sealant.html
    http://www.kent-gaskets.co.uk/our-products/ptfe-products/expanded-ptfe-joint-sealant/

    basically, if it didnt work, i wouldnt recomend it!

    i still prefer thin copper shim myself, re-annealed every time the heads removed. i got the tools to make them though.


    the grooves in the sealing faces are just as old a trick as using teflon tape in engineering practise ;) combine the two and everythings peachy :)
     
  17. jaguar

    jaguar Well-Known Member

    Fabian, the cylinders I have (48cc, 55cc, 60cc) do not have that lip so now I wonder if all the 69cc cylinders have that.
     
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