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  • Manifold Leaks-- Still!

    Hey everybody,
    I'm really bad at sealing my intake manifold. I've never gotten it to seal properly and it's always run poorly as a result.
    Currently I have a year old hand ported manifold, I surfaced it some on the mounting but didn't even take all the green off so I don't think I removed too much material.

    The orings are new too but they've been installed a few times. I've installed this manifold a few times and the old one several times, but never resolved the leak. The last two times I used a little permatex perma seal (fuel resistant, like yamabond) with no real success. Resealed last night, it's worse than ever.
    Can't find a comprehensive step by step this works every time deal for mounting a manifold and hsr42 so it won't leak any more. Thanks.

  • #2
    are you sure your not leaking where the carb meets the intake? there is a little spacer in the clamp for the carb. some have removed that spacer so they can crank down the clamp a little more.

    at the flanges i got a perfect seal everytime with hylomar. best thing is its non setting so you can remove the parts easy and scrape off the old stuff with a simple putty knife
    my Wallet is Getting dangerously close to spontaneous combustion

    Comment


    • #3
      I'm fairly sure it isn't the clamp, my spacer is removed and I bottom the screw out. Do you use a lot of hylomar on it? I've been pretty soaring with it. Still use orings with the hylomar?
      One idea I have is that the screws bottom out in the head. Maybe they're hitting bottom before flange is tight. I got some washers to check that theory and will reseal it again, but I'm still open to suggestions for when I do it.

      Comment


      • #4
        Yes. You still use the orings with the Hylomar.
        Did you surface the manifold flanges?

        When installing the manifold, finger tighten the bolts. Then start turning each bolt in about an 1/8 or so at a time, working back and forth from one side to the other alternating which bolt you snug a little each time, until your tight on all four.

        I use small washers under the bolts to help spread the pressure on the thin flange. I think I got that idea from Curt.

        I know davej had issues on his 05(?), and ended up making gaskets.

        Comment


        • Spydr
          Spydr commented
          Editing a comment
          I finally went DaveJ's route and made fiber gaskets. Worked so well I've forgotten how long ago I did it.
          I do remember that it was when I got Curt to port a manifold for me. So maybe 30K miles?

        • Jclevesque
          Jclevesque commented
          Editing a comment
          Spydr I would like to know more about the fiber gasket that you reference from Davej. What kind of material and where did you purchase.

        • Spydr
          Spydr commented
          Editing a comment
          Jclevesque, you have a P.M.

      • #5
        Ok, I will use the orings too. Yes I surfaced them, just not a ton because I was concerned about the fitment if I took too much off. There is a little bit of green left on the flange surfaces.
        I have a single washer on each bolt which I believe is stock, but I'll use more next time around.
        Davej is a guru, he's given me a ton of good advice. Maybe he's onto something...

        Comment


        • #6
          Looks like you got your answer on the hylomar and orings. Also make sure your vacumb ports on the backside of the carb and manifold are capped and not leaking
          my Wallet is Getting dangerously close to spontaneous combustion

          Comment


          • #7
            Tried the whole thing over tonight with motoseal, clean orings, clean surfaces, and two additional washers under each screw to make sure I'm getting the manifold down tight. Letting the gasket maker set before a test ride. Fingers crossed.

            Comment


            • #8
              That didn't work out like I hoped. Still has severe vac leak on both cylinders.

              Comment


              • #9
                You don't need any sealer just some grease on the O'rings and tighten the bolts in stages as previously mentioned. So what makes you think you have a vacuum leak? If you spray anywhere around the throttle shaft you'll get an indication of a leak. Also make sure the coasting enricher cap isn't cracked.

                The best way to check for a vacuum leak at the manifold is to let the carburetor hang loose, block off the manifold inlet, and draw a vacuum on the manifold through the nipple on top. Mine will hold 25" for 5 minutes. This can be done because our engines stop with both sets of intake valves closed. Of course this method is also testing the valves and stems for leakage.
                Scott B.

                Comment


                • #10
                  I've been using carb cleaner with the tiny straw, pointed right at the manifold to head joint. I can kill the engine like that if I want to. Also, the engine runs like it has an extreme leak- rough at very low throttle, jerky and stuff. Your method sounds cool I might try that, but I'm using the sealer because it never sealed with just orings.

                  Comment


                  • #11
                    I thought mine wasn't sealing good either. Tried various sealants also to no avail or so I thought. I had even sanded the flanges flat. Finally cleaned the sealant off the flanges, greased the O'Rings and that was it. Used the method I mentioned and found out there was actually no leak. If the flanges are flat and the O'Rings greased the manifold will seal, period, that is as long as the head surfaces are clean and smooth.
                    Scott B.

                    Comment


                    • #12
                      I'll give it a try, thanks.

                      Comment


                      • #13
                        I'll add what may seem obvious to most on here but be careful to tighten it down evenly a little on each bolt at a time so it stays square to the head.

                        Comment


                        • #14
                          Originally posted by texasscott1 View Post
                          I thought mine wasn't sealing good either. Tried various sealants also to no avail or so I thought. I had even sanded the flanges flat. Finally cleaned the sealant off the flanges, greased the O'Rings and that was it. Used the method I mentioned and found out there was actually no leak. If the flanges are flat and the O'Rings greased the manifold will seal, period, that is as long as the head surfaces are clean and smooth.
                          I have done several, and never used anything but grease... If properly prepared that is all that is needed with the new o rings. If surfacing block is not available, you can tape a piece of 400 grit paper to a glass pane and it will make it sand even.. It is a shame no one can build a intake that does not crack..... I have put 3 on my bike, and 2 on my sons. I do not wait until they start to leak, I replace when they get severe cracking. Oh Yea, put some washers under the head of the bolts.

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