Home Forums Shifter Karts CR125 How to Seal Exhaust

This topic contains 10 replies, has 7 voices, and was last updated by  James O’Brien 4 years, 1 month ago.

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  • #51955

    Todd Kageals


    My CR125 Stock Honda blows oil out of the exhaust manifold all the time.  I replaced the 4 o-rings and the one on the back side but by the end of the 1st race they were literally gone!  I’m using the 4 o-ring manifold.  Is there another option or a different kind of seal?



  • #51968

    Randy McKee

    Hi Todd,

    Wow they up to 4 rings now on the manifolds?  I have 3 after-market manifolds; two with 2 rings and another with 3 and I think the 2 worked better.  They both seemed to last for about 3 to 4 track days with the viton o-rings.

    The biggest problem I ran into with the o-rings was trying to get the pipe over them without cutting them.  I think that’s why the 2 rings worked best (easier to get the pipe over just 2 o-rings).  Not sure if that’s what you are experiencing. If so, try using just 2 rings closest to the motor and use plenty of lube when putting the pipe over them. Also, make sure your o-rings are the proper size.  I know there are at least 2 sizes out there.  If the rings are loose, they are too big and won’t seal very well.

    BTW: The after market manifolds/o-rings became such a pain in the buttox that I went back to the stock manifold with rtv silicone.  Much easier and it last a couple of track days.



  • #51990

    Bill Cox

    Spray some WD40 on your finger; wipe the O-rings and inside of the pipe; then slide the pipe on while keeping it straight.  A little twisting of the pipe while it is slipping on helps, too.  It’s more technique than anything.  But I’ve found the WD40 works well.  It evaporates quickly when engine temp gets things warm.

  • #52001

    Todd Kageals

    Well….I don’t think that’s my problem.  I lube the O-rings every time and I use the Viton rings sold by sharkshifter who also sold me the manifold.  What about the stock manifold with the stock OEM seal?  Anyone try that?  Isn’t the stock seal a thin/wide metal ring?

  • #52013

    Sanford Mitz

    I’ve always used Permatex High Temp Silicone sealer (Orange)

  • #52051

    Alan Sheidler

    First thing to do before installing new o-rings is to use a piece of Scotchbrite pad to take all of the gunk out of the pipe inside, and be certain that the surface is really free from any nicks or deep scratches.  Same for the exhaust manifold, in particular the grooves.  They should be CLEAN.

    For years, I only used a bit of clear silicone lubricant that came from NAPA on the o-rings and inside the pipe.  But I have found that they last longer if I use some of the silicone sealant that Sanford refers to.

    I’d be curious how well the pipe and manifold fit.  They should be tight and not easy to bring together when the rings are on the manifold.  The one other thing not yet mentioned is the springs used.  If they are not strong enough, too much chafing will result, and premature failure of the o-rings will result.

  • #52062

    Todd Kageals


    I’m fairly certain that the spring are strong enough.  It’s fairly difficult to get them off and I doubt the pipe moves much at all.  The inside of the pipe looks clean but I will double check as you suggest.  The exhaust manifold groove are free from gunk but at least the last three grooves have some surface rust.  I might run it though the sand blaster to make sure it’s clean.  I’ll also try some of the high temp RTV you mentioned although I can’t even get that stuff to last back on the other end of the pipe between the pipe and the silencer.

  • #52067

    Alan Sheidler

    Blasting leaves a texture, better to use a 200 sandpaper intended for use on metal, and finish with a few passes of 600.  But try to avoid rounding off the edges of the grooves.

    The high-temp sealant that seems to work for me is the kind of copper-looking stuff.

  • #52103

    Todd Kageals

    I’m not sure I could sand down in the grooves with the paper.  I’ll use some walnut shell blast media or some ultra fine glass.  That should take care of the rust without leaving the surface too rough.  I’ll definitely try the copper RTV.  What brand do you use?

  • #52296

    Abraham Jones

    I had a similar problem and the culprit was the front motor mount. I had a two o-ring exhaust manifold and I was replacing them all the time. I finally noticed damage to the front engine motor mount and I had to replace the damaged half of the case and put in aluminum shims to get a good tight fit. After that, I could get two or three practice session and a race out of set of o-rings.

  • #52520

    James O’Brien

    Todd, it sounds like maybe your pipe is not square on the manifold or you have a manifold that has the grooves cut to deep (it happens). I would suggest going back to the stock Honda OEM manifold and sealing ring. This is if your pipe is not worn out. On our 99 and 01 engines we don’t have any splatter problems using the SKUSA S-1 Pipe, if we do usually it’s because the pipe needs to be adjusted.


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