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Is This Manifold OK?

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  • Is This Manifold OK?

    I was going to port this, but, well...

    Could I maybe use like a high temp RTV to patch up where it's cracked? I think I read that someone was repairing cracked manifolds but I can't find info on how. This one wasn't leaking, I just don't like the look of those ports.

    I'd rather not have to buy a whole new one! I'm trying to save for an ED seat to replace this old Ultimate one, haha.

  • #2
    Wow... I've seen them cracked on the outside, but never on the inside. Cracks on the outside usually aren't a problem, the rubber on there is thick. I'd try grinding the inside [porting it] and see how deep those cracks go. Try shining a light inside and check if you can see through any cracks. If so, time for a new manifold. I'd also get new o-rings too. The factory ones are known for failing sometimes once the seal is broken.

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    • #3
      The inside is cracked all the way to the metal insert. The rubber there is very thin. It also feels pretty oily right at those openings, and I noticed right after posting here that I have a bunch of oily gunk on top of my intake valves. There's even a slight bit of fresh oil just chillin' there. All 4 valves. Been getting a little oil from the crank breather too. So I guess all my valve stem seals leak or something.

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      • #4
        Kinda bummed because I assumed this would be some fairly quick work, but 2 of the 4 float bowl screw heads stripped as well, and while I have replacements for them too I just see how this is starting to go for me.

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        • #5
          Metal showing on the inside isn't an issue, that's normal. You'll actually remove some of the metal when you do the porting. The oil is from the crank case breather attached to the intake boot behind the air filter. It would be a good idea to get yourself an aftermarket crank case breather filter. Then plug the opening in the back of the intake boot. It may not be necessary to reject your carburetor. How was the bike running? Do you smell unburnt gasoline from the exhaust? Does the idle stumble every couple seconds? Have you tried the test for SVS?

          Get some Berryman B12 Chemtool and squirt a healthy amount on the back of the intake valves and let them sit at least a couple hours. It might be a good idea to do the same for the exhaust vales too if your idle stumbles. Then add about a third of a can af SeaFoam to a full tank of gas and ride it like you stole it until you use up the tank of gas.

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          • #6
            I'll take metal off of the head-end of each insert?

            I've actually had the crank breather run to its own filter, so the oil isn't from that.

            I took the carb off because I wanted to rejet for a new airbox, and was going to port the manifold while I was at it.

            Bike runs good, don't notice gas smell once the choke is off, idles fine (just doesn't want to kick all the way down until I shift to N). Haven't done SVS test, though.

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            • #7
              I wouldn't use any kind of sealant on the inside of the manifold. Just takes a small shred of it to come off and jam up the oil pump.


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              • TimB
                TimB commented
                Editing a comment
                Yes sir, you are correct!

              • Bikerron
                Bikerron commented
                Editing a comment
                Seems that would entail some serious blow by to go from the combustion chamber to the crankcase pick up tube, with screen, to the oil pump.

            • #8
              Then I wouldn't worry about the exhaust valves. If it's not stumbling at idle, no need to worry about SVS test either. BTW, when I say, stumble, i mean it sounds like t skips a beat every once in a while. If it's only an oily film or a baked on layer of varnish on the intake valve, just do the SeaFoam in the gas tank, if it's caked on, then do the B12. It may have been from before you rerouted the breather because there's no other way to have oil in there unless it's in your gas.

              Not sure what you mean by taking metal of the head end, are your talking about resurfacing the the mating surface with some sandpaper? If you plan to make your own paper gasket to replace the o-rings, that will help, otherwise it's the o-rings that do the sealing, and if you remove a little too much, the o-rings won't stay in the groove when you install. [I've had that happen before] And I know some here have suggested using blue sealant on the face of the manifold, but I personally wouldn't. I've tried it a couple time too and it just made a mess and it reacts with the paper gasket causing it to break down.

              Are you talking about the idle hanging for a moment when you shift to neutral? Then yah, jetting can help but make sure to adjust the accelerator pump. That needs to be done on the bike with the motor running. Check for the how to in the Tech Articles section. And FPB is right, be careful with putting anything inside the manifold that could find it's way inside the motor. If you have any cracks that go all the way through then just replace it. If you have some small hairline cracks on the outside, that go all the way through, you can try coating the outside with PlastiDip or something similar, but it's only a temporary fix.

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              • #9
                Gheez! Replace the manifold It's time! $65 part is all, your ass will wait, this won't.

                Comment


                • Scionreality
                  Scionreality commented
                  Editing a comment
                  I guess I assumed it would be $200 like it always seems to be.

              • #10
                Originally posted by Doc_V View Post
                BTW, when I say, stumble, i mean it sounds like t skips a beat every once in a while.
                When I get it back together I'll take another listen to be sure. It might be one of those things that always sounded like that and wasn't startling so never thought much of it.

                Originally posted by Doc_V View Post
                ​​​​​​Not sure what you mean by taking metal of the head end, are your talking about resurfacing the the mating surface with some sandpaper?
                At the end of each runner where the flange mates to the head, the inner diameter at that mouth is where it's all cracked down to the metal on each side. One little chunk, one each side right at the mouth, has even flaked off and hopefully been blown out. I intend to resurface the flanges, but thought you were talking about port matching that ID to the head's intake port, and that it would mean getting down into the metal.

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                • #11
                  To be clear, when we talk about "porting" the intake manifold, we're referring to honing out the inside of the manifold to remove unneeded material. If you look, you'll notice with the rubber on the inside of the manifold [the inner diameter [ID] of the manifold] it's actually *smaller* then ID of the intake port on the head. The idea is to remove the unneeded crap [both rubber and aluminum] from inside diameter of the manifold so it more closely matches the intake port on the head.

                  Here's a stock manifold ID vs ported:

                  Click image for larger versionName:	s-l300.jpgViews:	1Size:	14.5 KBID:	71281Click image for larger version  Name:	RSPIM.jpg Views:	1 Size:	6.2 KB ID:	71282

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                  • #12
                    Oh, yes, matching the port diameters. I hadn't measured it yet and didn't know manifold was so much smaller. The rest of mine looks great. I didn't realize so much material needed to come off the ID.

                    Thanks for that clarification, Doc. All this time I thought when they said "don't be alarmed if you hit metal" people were referring to the inside corners when rounding them off.

                    Edit: to be clear, only the rubber on the inside of each runner toward the opening where is covers the aluminum is cracked. I checked over the rest of it and the rubber appears to be in good condition without cracks or noticeable hardening.

                    Comment


                    • #13
                      Glad to hear. More often than not the cracks are superficial.

                      Comment

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