How To Seal Ram Air Tubes, Gen 2


Ram Air Tube Sealing
It’s sometimes suggested that the seams in the ram air tubes on the Gen 2 Hayabusa should be sealed, the thought being that eliminating all possible air leaks in the tubes will maximize the ram air intake effect.

While I had the ram air tubes removed from my 2008 Hayabusa, I had the opportunity to run the motor and feel the intake pulses. I did not measure the intake suction with a vacuum gauge but I placed my hands over the intake passages that pass through the frame and lead into the air box. I felt a weak suction with the motor at idle and stock air filter installed. Revving the engine to 6000 rpm still did not produce a strong draw but I was able feel a subtle increase in suction against the palm of my hand. I did not run the motor any higher than 6000 rpm and I did not try the experiment with a high flow air filter.

Albeit crude, the experiment indicates that the demand for air from the motor is much less than the volume supplied by the ram air system. It would seem unlikely that a small amount of leakage from the ram air tubes would have a meaningful effect on the volume of intake to the motor while it is running below 6000 rpm with the use of a stock air filter. High speed/high rpm operation may be impacted by eliminating all leaks from the ram air system. I’d estimate the improvement could only amount to a measurable increase in horsepower at speeds well over 100 mph.

It’s possible that the main purpose of ram air is to provide cool air to the motor and that the ram effect has nothing to do with increasing flow. Increased pressure of cool air can only help keep the air temperature in the air box lower. In that respect, the ram air tube seal might produce benefits beyond (or in addition to) increased flow of air to the motor.

Unless you are LSR racing, I’d put the ram air tube seal low on the list of mod priorities. If you have some spare time on a rainy weekend, you might want to do the mod just for peace of mind. Also, the ram air system is only half sealed until you seal the seam between the frame and the air box. Aftermarket seals that allow easy air box removal should be used for this. I plan to do this mod in the near future. I’ll post a tutorial when I do.

Each ram air tube is configured in halves that secure together by wedge-like clips and slots. There is a seam all the way around each ram air tube and as you can see in photo A, the seam leaks water. In photo B, the seam has been sealed with silicone and water pours only from the ram air opening and exit with no leakage from anywhere else. It should be noted that water, being much denser than air, will force its way through small spaces more readily than a gas that is under light pressure (such as air entering the ram air tube with the bike operated at speed). The water test shows that there is at least a potential for air pressure to escape through the seams. Silicone makes the seam watertight so it should seal a reasonable amount of air pressure as well.

The seam between the ram air tube and the frame needs to be sealed as well (see steps 8,9 of this tutorial).

Photo A, no seal, seam leaks

Photo B, sealed, no water leaks from seam

The OEM fairing grommet in each ram air tube should also be sealed. A more direct solution to the loose fitting grommets would be to remove them, patch the holes where the grommets fit into the ram air tubes and cut the mating fairing projections off. The projection’s main purpose is most likely to position the fairing rather than to play a role in securing it.

I replaced the OEM grommets (which often got pushed out during fairing installation) with a modified 5/16†well nut. This fits very snug in the ram air tube and it also seems to fit tightly around the fairing projection. At the very least, it will not fall oin the ram air tube like the OEM grommets do. I was able to find the well nuts at Lowes. for $1.75 a piece.

Caulk gun
Denatured alcohol and clean rags or paper towel
1 tube of silicone sealant (I used clear GE silicone sealant but a high-temp silicone may be an even better option.)
Razor knife
2 five sixteenth inch well nuts

DO FIRST:Remove the Rear View Mirrors (see steps 1-2

Remove the top fairing (see

Remove the ram air tubes (see

1. Wash off the seam around the ram air tube with a rag moistened with denatured alcohol.

2. Apply a bead of silicone sealant all the way around the inside seam with caulking gun.
If you are a perfectionist and wish to do the neatest possible job using the minimum of material, you can wipe off the excess sealant to leave a thin film in the cracks and crevices. Let it dry and apply another thin layer of sealant over that.

Plastidip may be a more easily removed and equally good sealant. Might want to try that product instead of silicone.

3. After the inside seam has dried, turn the tube over and seal each of the slot and wedge joints with silicone sealant.

4. If the OEM grommet is still in, push it into the ram air tube from the outside and remove it.

5. Use a razor knife to cut a 5/16†well nut along the length where the metal nut is vulcanized to modify it as a fairing grommet replacement.
It’s a lot safer to place the well nut on a table rather than hold a finger under it as shown in the pic.

Squeeze the hollow length of the well nut with a needle nose pliers to break the rubber completely.

Pull off the portion of rubber that contains the nut. One perfect sealing, never to get pushed inside ram air tube fairing projection grommet, done! Now make one for the other side.

6. Press a modified well nut grommet into each ram air tube.

As you can see the OEM grommet has a thinner flange than the modified well nut grommet. The rubber flange on the well nut grommet fits the space between the fairing and the ram air tube snugly.

7. Install the ram air tubes (see steps 6 and 7,

8. Install the top fairing (see steps 9-15 reverse, and tightened the screw that secures the top fairing to the ram air tube on each side. This will ensure that the ram air tubes (which hang somewhat loosely) are securely positioned before applying silicone to the seam between the frame and the ram air tube.

9. Use denatured alcohol on a clean cloth to wipe the outside of the area where the ram air tube inserts into the frame.

10. Lay a bead of silicone sealant along the seam where the ram air tube inserts into the frame. The medial surface of the tube/frame insertion is difficult to reach with a caulk gun. The sealant will need to be applied with a finger.

11. Install the dash panels (see steps 1-8,

Weight Increase
The grommet mod reduces weight by .05 ounces.

This is offset by the added weight of the silicone sealant.

Net weight increase: ~.55 oz
I'd like to try a pressurized smoke test on the system some day. No doubt there would be leaks in the airbox. In fact, if you really want to seal the airbox, I imagine you would need some sort of gasket around the edge of whole cover.

As far as the grommets on the sides of the tubes, that should sealperfectly well provided the fairing projection lines up well to the hole. Seems to work on mine but again, I'd need to do a smoke test. I left the fairing installed for 3 days with the modified well nut. It came off fine and was reinstalled. Seems to fit nice and snug but I just want to ad a word of caution....seems possible that projection MIGHT bust off if the fit is too tight now. I have not ridden the bike yet so I can't say. I doubt it wil be a problem but just thought I should mention it so peoples don't get mad at me should a fairing projection break off.
The bike has sat for a couple of weeks in very cold garage. I am doing some work and needed tpo remove the left side fairing. It came off just fine everywhere except the modified grommet in the ram air tube. I decided to use a large straight slot screwdriver to wedge between the grommet and the place where the grommet sits against the inside of the fairing. I twisted the screwdriver to pry the projection out. This will require removing a section of the dash panels on each side every time I remove the side panel. I know there are many owners who will not want to bother with this but I will for now. Some day, I will probably just cut the projection off and seal off the grommet hole in the ram air tube.

After a couple years, the well nut hole has stretched enough that the projection comes out without a problem but since that is the case, I know it is also leaking air.
Seven years later, still got the GM silicone on there. It seems to pull loose without too much effort if I pick at it with my fingernail. Good to know it can be removed easily if I wait long enough. Those modified grommets I stuck in there are stretched and they even look like they are trying to push into the ram air tubes like the OEM ones do. I will probably take those out and try gluing the OEM grommets into the ram air tube with silicone.
If you wanted to seal them well, why not just use Flex Seal®?
I think the silicone is better if it comes off easier. Never know when you might want to reverse the mod. It looks kind of sloppy. I might use black RTV if I did this again. Actually, the thing that seems best would be to wrap the ram air tubes in vinyl. The grommets....I think it might be best to just cut the projection off the fairings and patch the hole with a flat piece of plastic.