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Suzuki 800 Intruder Club & Forum

A UK Site Dedicated To The Suzuki C800, VL800, VX800, M800, VZ800, VS800, C50, M50 Model Intruder / Boulevard / Marauder
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 2nd air question vz800

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PostSubject: 2nd air question vz800   Sun May 18, 2014 8:58 pm

whats up everybody! i noticed some people take off the 2nd air from the side of the motorcycle. I am a fairly new rider and trying to learn parts and its functions. Does anyone know anything about it? I was trying to relocated it or either take it off if it doesnt affect the engine. Thank you guys
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* VZ Guru *

PostSubject: Re: 2nd air question vz800   Sun May 18, 2014 11:35 pm

Hi Gnarbino,
I have been doing pair valve removals for years,,, reference the VZ I am going to be lazy and copy some stuff for you, and any interested brothers and sisters on the forum, from my library of bike knowledge instead of writing it myself. 
firstly what a pair valve is and what it does and why,, the removal of the pair valve refers to a kit of parts you can buy but to be blunt,, it`s piss easy to make the bits you need to do the job,,,this explanation and removal is also for Volusia`s  VL`S VX`S  LC`S excreta,, there all much of a muchness,,,, any way enjoy the read.

The Pair Valve, or "Secondary Air System" is a pollution control "Passive Air Injection" device, designed to "wash out" the purposely rich exhaust of the new metric bikes in order to pass EPA restrictions for import in the United States and other countries with similar restrictions. Many foreign designated models do not even come with a pair valve, although all other aspects of the bike's engine are the same. (The triangular (or oval) box is a tool box on most foreign models)
The sole purpose for the Pair Valve is to passively "Inject" fresh air into the exhaust system at the exhaust port, to cause ignition of unburned fuel vapor *before* it leaves the exhaust pipes, or to thin out the mixture with enough air to fool the sniffer machines. Unburned fuel vapors enter the exhaust system whenever you back off the throttle, or gear down. When you close the throttle, as in gearing down or slowing down, the drop in vacuum at the intake port allows the Pair Valve to relax and open and allow air from the air filter box to be "siphoned" into the exhaust port by the negative pressure at the exhaust ports. (there are reed valves in the pair valve to prevent backflow from the exhaust to enter the pair valve and airbox during roll-on and subsequent positive exhaust port pressure).
On the rare occasions that the pair system is working as designed, there is no erratic popping or gurgling in the exhaust system. There should be either no additional sound at all, or a steady "afterburn" effect, similar to an eighteen wheeler's "Jake Brake", a compression release speed reducer for large trucks.
Many people who have replaced their exhaust system with louder, lower backpressure pipes, have experienced an increase in the rapid popping/gurgling noises when throttling back and gearing down. With less backpressure, the exhaust vapors tend to load up in the system, and ignition of these vapors is sporadic and annoying. This popping occurs further down in the pipes, and is louder because of more open baffles, or no baffles at all. The quick fix for this is to simply "plug up" the air tubes that go into the cylinder walls, thereby preventing the air from getting there in the first place, thus, no "in-the-pipe" ignition. You may still experience some occasional popping, set off by the intense heat, but it is much less frequent.
Removing or disabling the Pair Valve will have no ill effects whatsoever to the bike even if its is still stock. The pair valve system will likely clog with carbon after a year or so, and quit working anyway. Removal is simple, and will take less than an hour once you have all the "stuff" together.

The presence or absence of the Pair Valve does not affect your fuel mileage, power, or general engine running condition. It's purpose is solely to thin out the exhaust mixture so that it will pass all available emission control standards, and this "thinning out" occurs at the exhaust ports *after* the pistons and spark plugs have done their job.
If you completely remove the Pair Valve from the bike, two air inlet holes will be left in the cylinder casings that must be blocked off with solid plates, an airbox outlet nipple (LC Models) and a vacuum nipple that must be capped, and if you choose to remove the chrome Pair Valve Housing box, there will be three 6 mm screw holes that should be filled, to give a finished appearance to the engine.

"After removing my pair valve, I am still experiencing that annoying "popping" upon deceleration. Did I do something wrong?

Leaking header joints, and pair valves are both causes for ignition of fuel vapors upon deceleration, as well as an improperly low idle speed, or improperly adjusted idle mixture.

First and foremost, make sure that your header nuts and bolts are tight, so there is no air leakage at the header gasket.

A very common issue with the LC is its tendency to let its idle speed "wander" a bit over a period of time. If it "wanders" down, you'll get the popping and gurgling on deceleration, and/or if the idle mixture is not right, you can still get it. AND, if everything is perfect, you're still going to get some popping. It's the nature of the beast. Big Bore V-Twins have never been efficient at complete combustion of their fuel mixture, and when you add in a second carburetor, you just get twice the inefficiency. Simple heat from within the exhaust system will still occasionally cause the ignition and thus, the noise.

The less backpressure from the exhaust system, the more air can climb in from the back side and feed the fumes enough to cause the proper mixture for exhaust ignition, so that's pretty much a given for the aftermarket pipes.

Here's what you need to do: when you are out riding, and you are getting the popping quite frequently when backing off, reach down and adjust your idle speed up just enough so that you can tell you've increased it (only takes a tiny bit), and ride some more, and see if it makes a difference. If not, then you may have to have your idle mixture screws adjusted a little to richen up the fuel just a tad.

And here's how to do it,, remember the piece refers to a kit of parts (you can buy them if you want) but are very easy to fabricate for yourself.

 NOTE** The only tools you will need for this operation are a pair of pliers, a small hex (allen) wrench, and a 10mm wrench. These can be found in your Suzuki Tool Kit. (Add a second 10mm wrench if you plan to remove the cylinder studs).


Remove the two button head screws that hold the chromed Pair Cover on, and pull off the cover and name plate.
If you only wish to disable the pair valve, but not remove any of it's components, insert a round headed screw into each of the two rubber air delivery tubes. Leave a small portion of the threaded end sticking out of the top of the rubber tube (for removal later if necessary), and re-install the tubes to the valve, then replace the cover.

· With a pair of long nose pliers (or your fingers) loosen and slide the tube hose clamps toward the center of the rubber tubing on the two air delivery tubes (the ones that go to the cylinders) and the small diameter vacuum tube.
· Pull the rubber air delivery tubes and vacuum tube loose from the valve.
· Using a 10mm wrench or socket, remove the three bolts that hold the housing to the cylinders (two upper corners, and lower left corner).

· Pull the housing (valve still attached) straight out from the bike, and away from the hoses and vacuum tube, and set aside.
NOTE: If you wish to retain the cover housing, you should remove it, to allow access to the vacuum nipple that must be capped, then you can remove the valve from the housing and re-install the housing.

· Remove the metal air delivery tubes from the cylinders, and make sure that no gasket material remains on the cylinder.

Front Cylinder - Right side of bike

Rear Cylinder - Left side of bike
· Remove the small diameter vacuum hose from the intake manifold (just twist and pull straight off)
 Cap off the manifold nipple with the rubber vacuum cap from the kit.
· For the better appearance, pull the studs from the cylinder flanges, then use four of the supplied 6mm bolts to attach the supplied plates and gaskets to the air delivery tube mounting surfaces on the cylinders.
· Gasket sealer is not necessary, but if you have it, I do recommend that you use it.

Front Cylinder - Right side of bike

Rear Cylinder - Left side of bike

If you haven’t pulled studs before; thread the original two nuts on one stud and tighten them very tightly against each other (opposite directions toward each other), then put a wrench on the inner nut, and as you try to "unscrew" it, the whole stud will unscrew. You may have to apply a little "counter pressure" to the outside nut with another wrench at the same time. It may be a bit difficult to work with the inner nut, due to the proximity of the cylinder fins, but you should be able to unscrew it with the outer nut (I did). Just make sure you get the two nuts very tight against each other first.

Front Cylinder - Right side of bike

Rear Cylinder - Left side of bike

- Bear in mind that anytime you work with studs, you run the risk of breaking the stud off, requiring difficult drilling and tapping to replace it. Pre-soaking the threads with penetrating oil, and a few light taps straight on the end of the stud will help break loose the hold of any corrosion inside. If the stud seems to require a lot of force, leave it be!

Use the three M6-1.0x10mm (shorter ones) Stainless Steel bolts and lock washers to fill the empty holes in the cylinders left by removing the housing.
YOU’RE DONE!! Don’t you wish YOU could loose five pounds of ugly fat that easy!!!

Here in the UK the VZ 800 does not have a pair valve,, the box is in fact a tool box.

Hope this is of some help to you mate and that it answers your questions.
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Mr Intruder Founder ... & ... Senior Administrator

PostSubject: Re: 2nd air question vz800   Mon May 19, 2014 8:35 am

Great information which answers a lot of unanswered questions.  
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captain crash
Mentally Deficient lunatic ..... & ..... Site Moderator

PostSubject: Re: 2nd air question vz800   Mon May 19, 2014 2:23 pm

Wow what great information  
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PostSubject: Re: 2nd air question vz800   Mon May 19, 2014 4:10 pm

awesome! thank you very much brother!    
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Very Valued VIP Member

PostSubject: Re: 2nd air question vz800   Mon May 19, 2014 10:20 pm

Excellent stuff John !
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* Site Guru *

PostSubject: Re: 2nd air question vz800   Mon May 19, 2014 10:35 pm

Interesting read!    
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