Intruders-Alert

Are the rubber airbox snorkels there strictly for sound suppression, or do they have a relevance to the tuning other than restricting the intake hole in the airbox lid? I know and understand that if you remove them, more air will be allowed in resulting in a leaner condition that has to be compensated for, but will you lose anything else other than noise reduction?

I am currently running K&N drop ins, Dynojet stage 1 kit set on the 3rd.clip position (stock jets), factory headers, Vance & Hines Classic II slip ons, and a Dynatek 3000 set to curve 4. Would I be able to compensate for the extra air from removing the snorkels with a fuel screw adjustment? Will the factory headers flow more?

Bloody good question Forge - I look forward to someone smarter than me letting us know!

Well, I removed my snorkels and will adjust the fuel screws accordingly to try her out and see what happens. I won't be able to take her out and run her until tomorrow.

Just a guess, but maybe to reduce water ingestion when riding in the rain?

Actually, I think the snorkels are there to keep the airspeed into the filters up and to smooth the flow. Removing them might actually cause air flow issues and make the performance worse.

Herb is pretty much on the ball. The airboxes act as a bit of a reservoir and to smooth out the induction pulses and the snorkels act as a velocity stack for the higher rev range. As I have been led to believe.

[emoji41]

As good an answer as any. I don't know about performance as velocity stacks, as those usually go between the filter and carb, but reducing turbulence in the filter box seems likely. Of course, that's what velocity stacks do for the carbs while increasing air speed, so essentially the same function; guess the name could apply to the snorkels, too.

It is a big air box to house a big filter, it needs to filter air for 600cc. Its removal does not affect noise. Some engines do not like running without an air box , re jetting will cure that.

The equation is fuel economy x emission control regulations x performance

Contrary to popular beilef a CV does not need an air box unless it is incorperated into its jetting formula.


I have no air boxes and make my own jets with root canal files and a vernier guage.

Well I took her out for an 85 mile run without the snorkels and can say that she runs great. She ran good before, but I honestly can't tell any difference performance wise by the seat of my pants. I only had to do a minor adjustment to the fuel screws.

One definite difference is intake noise. She has a little more bark now. I can probably only hear it at highway speed because of my windshield. The front airbox now has a more pronounced sucking/hissing sound at idle and slower speeds that you can hear coming from under the fuel tank. It may bother some people, but not me. It reminds me of when I opened up the rear of my shaker scoop on my '79 Trans Am and was able to hear the intake sound inside the cab of the car.

Forge wrote:Well I took her out for an 85 mile run without the snorkels and can say that she runs great. She ran good before, but I honestly can't tell any difference performance wise by the seat of my pants. I only had to do a minor adjustment to the fuel screws

Thats what should happen. Many people get things all crossed up and think they need a new main jet. The idle jet 'and' dont forget the illusive transitions take the Mikuni BDS way above 1/4 throttle and beyond what text books says. The idle jet is the only adjustable jet on the jet circuit and it does not turn itself off it keeps working right through the range, however its effect on top end becomes minimal but is still there and can in most circumstances be enough for regular exhaust swaps or air box cuts

so whats the thought on removing the snorkel and cutting the box so that the drop in filter can get more air flow. I haven't looked at the front filter yet but I see how I can do it with the rear

Luis_o_98 wrote:so whats the thought on removing the snorkel and cutting the box so that the drop in filter can get more air flow. I haven't looked at the front filter yet but I see how I can do it with the rear

If you install a filter with greater air flow, you will probably have to change the jets; it may still be in the range the pilot jet can handle, but usually main and needle jet/jet needle have to change. Only throttle-chop testing will show how lean you may have made it (or a good dyno test).

WintrSol wrote:

Luis_o_98 wrote:so whats the thought on removing the snorkel and cutting the box so that the drop in filter can get more air flow. I haven't looked at the front filter yet but I see how I can do it with the rear

If you install a filter with greater air flow, you will probably have to change the jets; it may still be in the range the pilot jet can handle, but usually main and needle jet/jet needle have to change. Only throttle-chop testing will show how lean you may have made it (or a good dyno test).

Just changing an air box or a pipe will not need the main jet swapping. You will have to do some serious tuning to make a 1.4mm jet insufficient.

I doubt very much that no one will ride a 1400 on the road and even get close to a 1.4mm jet maxing out.

Thats 1.4mm per cylinder!!! I dont wish to be argumentative but the idle jet does not just feed the idle idle but feeds transition jets on the butterfly mouth and these will need more fuel.

Look how big the Suzi idle jets are in comparison to say a Harley and they have only 1 carb.


Harleys have a pump jet to compensate. This literally squirts fuel down the throat to transit from Idle to Needle, a poor way of doing it but it works.

The issue with cutting the box down and installing a filter that lets more air through is that the air is denser than with the more restrictive filter system, simply because the air pressure doesn't drop as much. Denser air means that the mixture will be somewhat leaner at the same velocity flow; it's not that the jet won't keep up, it's that it is metering the amount of fuel for a different amount of air. It's the same reason you should change the jets for operating at high altitudes; in that case, though, the mixture gets richer because of the lower air density.

The main jet meters the fuel to the needle jet only . The needle will need to be at full throttle and about full RPM for the needle jet to require more fuel than the main can feed to it. Think of it as a fuse.

I doubt anyone in the street will be able to max out the main with just an air box mod.

We are assuming the stock air box is restrictive, im not sure how this has been ratified butI doubt that the air box is that restrictive. If it was it would knock out emissions and thats not what a professional bike company like Suzuki would do.

However if your air box/filter was restrictive it would be at the top end only.At normal street driving it would cope.

If you keep your bike on the ground and don't try to take off you will be ok. One of the benefits of the CV carb is its ability to cope with air density.

Im not arguing for arguments sake its just that I have a *87 1400 and I don't understand how you could think more power is required.

Uncorking I understand can give 6 Hp but has this been tested ---is 6HP extra necessary. This will be at the expense of fuel economy!!!

My 87 has no air boxes well just a small bit to hold the fuse box and starter solenoid,I also have the battery where the rear air box was, the front has nothing, I have straight pipes with 28 inch 1 1/2 down pipes and cross over ( very important).

She is a viscous and angry bitch, don't let her idle fool you, It is very hard work around town with the throttle like a switch. It will pass anything but a gas station.

How I wish is was stock with a nice drivable temper.

There are many cases of taking out the air boxes and replacing the filters with higher flow pod filters, and the engine was noticeably leaner, when the plugs were examined. A CV carb works on air velocity, not air density, and attempts to maintain the same air velocity with changes in CFM (hence the name), and doesn't lift the jet needle out of the needle jet any more with reduced restriction pod filters at the same throttle setting, which is why it is releasing the same amount of fuel into a stream of denser air. Fuel/air mixture is weight of fuel mixed with a weight of air, so the same fuel in denser air means a leaner mixture, because a given volume of denser air passes more air, by weight. How much leaner depends on how restrictive the stock filters and boxes were, as compared to the replacements, but certainly leaner. Both the 1400 and 800 show signs of needing a change in the needle jet/jet needle and often the main jet, to increase the amount of fuel metered into the air at a given CFM. As you approach WOT, the needle will be completely withdrawn from the jet, and the main jet becomes the primary fuel flow control; some riders ride at WOT more than you may think, especially in the lower gears, so changing the main jet is usually done with the needle system.

A lean engine is a mean engine, but can also have hot spots slowly degrading the combustion chamber parts.

On the 1500's if you cut out the top of the filter or replace with a GMan open K&N you have to re-jet both main and pilots.

hillsy wrote:On the 1500's if you cut out the top of the filter or replace with a GMan open K&N you have to re-jet both main and pilots.

That what they may say to cover them selves from unsatisfied customers.

Re jetting is not easy its not a case of this bike uses this It just does not work like that. Do the Mod and see what you got.

You can not acheive full throttle by twisting the grip--that would be a cable operated slide. The CV carb needs full depression and that builds up from engine demand. You would need full throttle and almost full RPM I most certainly can not achieve that on any roads around here.

Fred wrote:

hillsy wrote:On the 1500's if you cut out the top of the filter or replace with a GMan open K&N you have to re-jet both main and pilots.

That what they may say to cover them selves from unsatisfied customers.

Might be different for the 1400's but with the LC it will barely run if you cut the top off the filter without jetting changes. The stock jets are really small for that motor.

hillsy wrote:

Fred wrote:

hillsy wrote:On the 1500's if you cut out the top of the filter or replace with a GMan open K&N you have to re-jet both main and pilots.

That what they may say to cover them selves from unsatisfied customers.

Might be different for the 1400's but with the LC it will barely run if you cut the top off the filter without jetting changes. The stock jets are really small for that motor.

Good luck.