Losing compression thru decompression valve

Discussion in '2-Stroke Engines' started by jefuchs, Jan 26, 2013.

  1. jefuchs

    jefuchs Member

    I installed a decompression valve, and it works great for getting the motor started easily, but I've noticed that a lot of oil accumulates around it. Looking closer, with the motor running, I could see that I was indeed losing compression there.

    I worry that simply tightening will risk damaging the threads, and still not fix this. I think I need to seal it with something. There are lots of sealers out there, but most say they are not suitable for head gaskets, which means that they probably are wrong for this application as well, as it is exposed to the same heat.

    I want to take it off, apply "something", and put it back on. X = something. Solve for X

    When I first installed it, I used blue locktite. I also added a threaded aluminum spacer, which may not be mating perfectly with the surface of the head. If not, it's only off by a little.

    I saw one thread that recommended spraying head gaskets with silver spray paint as a dressing for head gaskets. Would spraying the threads with high-temp silver paint, then using blue locktite do the job?

    The picture was taken before I got it running. There's black oil all over it now.


  2. jefuchs

    jefuchs Member

    After further searching here, I think maybe a gasket sealer might work. They say they can't take the heat of a head gasket application, but their rated temp seems to be higher than the temperatures that these little motors generate. Won't hurt to try, I guess.
  3. Fabian

    Fabian Well-Known Member

  4. HeadSmess

    HeadSmess Well-Known Member

    is it leaking from the thread itself, or the valve spindle? a recent photo would have been far more appropriate... ;)

    teflon tape. lpg/ hi temp type if youre really concerned but if your heads getting over 300 C you already have other issues...

    spindle leak would require a lil bit of grinding paste on the valve...
  5. Fabian

    Fabian Well-Known Member

    My cylinder head has seen the wrong side of 300 degrees Celsius doing low speed heavy haul and it was a terrifying experience, with a column of smoke rising rising from the top end of the engine, as all the caked on oil and crud turned to vapour. I was waiting for the imminent sound of silence as metal welded itself to metal, but the old girl kept on working her guts out.
    When it came time to replace the cylinder, the copper Permatex (used on the exhaust) was still in good condition. Since then i've been sold on Permatex products.
  6. jefuchs

    jefuchs Member

    Thanks guys. The copper gasket goo is in stock at my local auto parts place (according to their website), so after coffee I'll get out of my pajamas and head over there.

    I don't think I'd be able to do this hobby without knowledgeable people like y'all to turn to. I really appreciate that you're here.
  7. Fabian

    Fabian Well-Known Member

    That's what friends are for :cool: