Biglry's desmog mod for the VTX

Biglry's desmog mod for the VTX
Original mod by Biglry - updated pics and info added by me

Preface
This is a walk-through for removing the PAIR valve assembly and the secondary air system with all the hoses and junk that are associated with them. I am separating the steps involved into the PAIR valve removal (desmog) and the secondary air system removal since they are 2 entirely separate systems but have been lumped together for so long many people think they are one in the same. For those who wonder how much stuff is under the tank that doesn't need to be, here's what we're removing:

Lotsa junk eh?
I'll let Biglry sum up the mod since he wrote the book on it originally:

The Pair valve is nothing more than a way to get fresh air into the exhaust port to complete the burn of unburned fuel to meet federal smog regulations - it can be compared to the smog pump in a car. On a car it uses HP to turn an air pump (no pump on the VTX), and the air is injected into the exhaust manifold near the port. In the VTX and other bikes that use the PAIR system for smog control the air is pulsed directly into the exhaust port through a one way valve (reed valve) and a hole in the head to the exhaust port. There is a scavenging effect that a properly tuned exhaust has that helps with the flow of getting exhaust gases out of the combustion chamber. I have found through much testing in my building of motorcycles that the pulsed air at the exhaust port is detrimental in trying to build more HP through exhaust mods. As for RWHP gain on this mod on a stock bike, I doubt you would see a measurable gain.
Ever heard of any one changing header pipes, they go cheap and use the old gaskets then get popping on decel from sucking in cold air at the exhaust port? Well I have seen by doing this mod 99% of decel popping stops on a stock bike. Could it be because no fresh air is going in the exhaust port? I feel that it is why we see this decel popping on a lot of stock VTXs.
Now for the secondary air solenoid and flapper removal. Go to Honda and buy a new air box for your VTX - there's no flapper only a hole where it once went and they don't have the flapper for sale any more. Honda has eliminated this part as far as I know. One side benefit with the flapper assembly gone is you pick up 3% more available air to the air filter. You can also gain 2% more available air to the filter by removing the rubber snorkel. As for RWHP gain on a dyno run with a stock bike you gain less than 2 HP but this is a mod that I did in my quest for more RWHP to work together with other mods I've done like my "Twin Scoops". I also use a K&N filter.
Finally the EVAP canister on the CA model bikes, it dumps gas fumes from the fuel tank into the intake manifold at low rpm only, not when the bike is stopped. When the bike is stopped the fuel tank fumes are released directly into the atmosphere. I don't want any fumes going into my manifold unless it is controlled buy my fuel Injectors. Again any RWHP gain? By itself none, but as with all mods it is a item that helps others work better.
I would like to clarify a few other points. No where in my "how to" post did I say these mods where needed for the VTX or said any thing about RWHP gain or possible warranty problems. I tried to give a straight forward way to do this mod as there is a lot of myth and misconception that has arisen over these federally regulated emission parts of the VTX. In no way do I advocate anyone to break Federal emissions laws or state emissions laws ;-) and as Docc has said I know of NO Honda dealer that would violate Federal emissions laws (it's a big $ fine). The fact is without these Federal mandated and state regulated laws, Honda probably would not have put a PAIR system or EVAP canister, catalytic muffler, O2 sensor or any of the other emission specs on the VTX. The emissions equipment on my VTX is of no benefit to it's rideablity and makes no RWHP gains that I have found.
BIGLRY Out:-)

As always undertake this project at your own risk. I have detailed this write-up for the C model but the basic procedure is the same for all 1800 VTX's.

The original version of this mod recommended capping off the reed valves using rubber caps but over time we've found that these caps dry up and crack leaving you with unfiltered air getting into your motor and the need to refix the same problem every few months. In updating the mod here I recommend using block-off plates to alleviate this issue. German Pete's block-off plates are inexpensive and look a lot nicer than caps on the old valves too.
This project takes most people between 1-2 hours the first time, YMMV. I hope this helps!

Testing
For anyone that is interested in this mod but are afraid of what the end results will be you can test it out beforehand by doing this. Go to a local hardware store and buy a #000 rubber plug. ACE Hardware has the plug for less than $.25.
If you look in the airbox under the air filter you will see a small hole with a ledge on the left side of it. Take that #000 rubber plug and push it into that hole. You can smear a little RTV silicone on the plug if you want but it fits really well by itself and the ledge keeps it in place. Do NOT plug the crankcase breather!

Now some of you may ask why not just plug this instead of doing the entire mod?

This is an excerpt from VTX-Rated:

Disconnecting the pair valve wiring and plugging the intake hose will cause condensation to build up in the hose plumbing. Eventually it will fill with water and may cause white smoke out the tailpipe when decelerating (this happened on my bike). The deceleration caused the water to leak past the reed valves and into the exhaust stream. No damage was done to the engine it was just annoying. So if you want to disable the pair valve system remove it completely - otherwise, leave it intact and functioning.

In addition to the "smoke problem", as condensation builds in these hoses it can cause an annoying "gurgling" sound because eventually the PAIR valve will stick open allowing air to move from one reed valve to the other through the water. Bottom line, it's best to do the entire removal if you decide that you would like to keep the system inactive.

Preparation/supplies

10mm and 8mm or 5/16" wrench

10mm socket

5 & 6mm allen

1 - 1/8" rubber vacuum cap (available at most auto stores - CA models will need 3 of these)

Regular philips screwdriver

Small flathead screwdriver

Pliers

Electrical tape

RTV silicone (high temp variety)

Tank prop

German Pete's block off plates

If you still have the stock airbox you'll need:

big philips screwdriver, possibly an impact driver (for removing stock airbox)

1 - 1/2" rubber vacuum cap (available at most auto stores)

Process
Run the bike low on gas, this is not a mod you want to do on a full tank as it's heavy and you risk spilling fuel out of the tank vent line. Also make sure the engine is cold as I have burned my hand on a few that were ridden over for the work.

Remove the stock airbox cover and filter using the 5mm allen.

Don’t lose the 5 plastic washers that are behind these screws as Honda gets $2 apiece for them. Be sure to look for the big rubber gasket that the air box cover seals on but DO NOT remove it as it is a real PITA to get back in.
with a big phillips head impact driver remove the 4 screws that hold on the plastic velocity stacks and air box. Be careful when you hit the driver, you just need a little tap with hammer the driver does all the work. These screws are in tight and if you use a regular screw driver you may strip out the head. Remove the velocity stacks only at this time.

Now let's remove the seat by pulling these 3 bolts:

Now remove the 3 5mm bolts closest to the seat on the dash and take off the gas cap. Be careful to not lose the plastic washers behind these screws as well.

NOTE: Leave the gas cap on until you get all the screws out and away from
the dash - it is very common for people to drop the screws IN the gas tank during this step!
To remove the dash panel slide it forward a little and put the gas cap back on the tank. Be careful not to lose the little rubber piece that the dash slides onto on the tab on the front of the tank. Wrap the dash in a towel to protect it and lay it somewhere out of the way. Brace the front wheel/forks/handlebars so the bars won't flop around and ding the tank, and as a failsafe lay a heavy towel on top of the tank to help protect it in case something does hit it. With that done you'll see the 10mm nut/bolt that holds the tank to the frame down where the seat was. Remove that bolt and you can either prop the tank using Biglry's tank prop:

or lift and slide the tank back about 4" and lean it over at about a 45 degree angle to left side of frame (it will sit there just fine).
Now if you start to pull the airbox away from the bike you will see 2 hoses and an electrical plug going to the back of the box and one small vacuum line plugged into the flapper valve at the top of the airbox. The big hose is the PAIR inlet, the small hose is the crankcase breather and the electrical plug goes to the IAT sensor. Reach behind the airbox and pull off all 3 hoses and the electrical plug. The plug has a little tab you need to press to get it off. With this removed you should be able to get the airbox off the bike altogether.

Secondary air system removal
These are not necessary steps to complete the desmog (PAIR removal) but since the secondary air system really serves no purpose (Honda doesn't even make these parts anymore) there is no reason not to remove this stuff. I separate the 2 "parts" of this write-up only to make the distinction between what is the secondary air system and what is the PAIR system on the bike.

Take a phillips screwdriver and remove the screw that holds on the air flapper on the back of the airbox and remove the entire assembly. There is a little silicone that is used as a sealant but don’t worry it will peel right off. Nice big air hole there now.

Next to that new hole you have the snorkel. Removing it takes a little work but what I do is fold the rubber up and push it out the front of air box. It is also possible to do the same thing and pull it out the back of the airbox - whatever works for you. Once it is out you will have two big holes on the back of the airbox for the VTX to breathe through. You can also cut the back of the airbox to allow even more air, but I prefer to have every thing intact in case I ever want to reinstall it.

Ignore the 1/2" plug part (for now) as we'll get to that later.

Now looking just forward of where the PAIR solenoid valve is you will see the secondary air control solenoid and a small black vacuum canister with vacuum lines bolted in place with an 8mm bolt.

The vacuum line labeled #1 in the pic used to plug into the flapper on the back of the airbox and there is an electrical plug on the secondary air control solenoid. Remove the 8mm bolt, unplug the electrical connection and trace the last vacuum line (#2 in the pic) that is still connected back to the intake manifold, remove the vacuum line and replace it with the 1/8" vacuum cap.

Before

After

Take the electrical plug and zip-tie it out of the way. I usually squeeze a little grease in the plug and wrap it with electrical tape to keep it protected from the elements in case I would ever want to hook it back up.

This is the end of the secondary air system removal, you should now have all this junk off the bike:

Now on to the desmog process itself.

PAIR system removal (desmog)
At this point I'll assume that you've already followed the steps above up until the "secondary air system removal".

Grab the airbox and the 1/2" vacuum cap and cap the inlet where the PAIR hose (the large hose) went into the airbox.

Biglry used to recommend the 3/8" caps but many (including myself) found that these were nearly impossible to get on and would usually split in the process. The 1/2" caps work just fine. To ensure a good seal use a little RTV silicone in the cap, it helps with sliding the cap on and when it cures it will make a perfect seal. As you can see in the pic I use a small hose clamp to hold the cap in place while I work, this gives the RTV a little time to cure while I do the rest of the work.
You can also see the smaller hole where the small hose hooks to, this is the crank case breather, do not cap this line! It must be left open to vent the crank case. You will put this hose back on when you put the air box back on. If you cap, pinch or kink this line so it cannot vent when the bike is running you will blow the seals on your transmission and make quite a mess spraying oil around.

Now look at the backbone of the bike and you will see a 10mm bolt holding a wire bracket which in turn holds the pair solenoid valve in place. This is right next to where the secondary air solenoid was.

There are 3 hoses coming from this unit and one electrical plug. Trace the 3 hoses, one was the big hose that plugged into the back of the airbox and the other 2 go to the reed valves on top of the motor (one in front, one in back). Trace the hoses and pull them off the reed valves, after awhile they stick on there pretty well, but a little twist will help get them off.

With the hoses disconnected you can work on the electrical plug. Find this tab and instead of pressing it, lift it up with a flathead screwdriver to disconnect the plug.

With the 3 hoses and electrical plug undone you can remove the 10mm bolt on the backbone of the bike and remove this entire assembly. I do the same with this plug as the SAS one - squeeze a little grease in the plug, wrap it with electrical tape and then zip tie it out of the way.

Now with all that junk out of the way we will remove the reed valves and replace them with our block-off plates. Find the rear coil on the right side of the backbone back towards the seat and using a 10mm socket unbolt it from the bike. Be careful not to lose the spacers as you remove the coil.

Unplug the black wire w/ white stripe and the yellow wire w/ blue stripe from the coil and you should be able to rotate the coil back and out of the way to give us a perfect shot at the reed valve. With the coil out of the way take an 8mm or 5/16" wrench and remove the bolts that hold the reed valves in place.

I find it easiest to remove the right side bolt from the right of the bike and the left side bolt from the left. It is tight space and I have huge hands, so I know it's tight - just be patient and you'll get it. It will require a lot of small turns to get it loose and eventually you'll be able to spin it out with your fingers.
With both bolts out you can remove the reed valve cover and then reach in to pull out the gasket assembly.

These are the parts of the assembly you will remove from under the valve itself:

You'll need to disassemble these to get just part #4 by itself. If you don't remove parts #1, #2 and #3 the screw will prevent the plate from making an airtight seal, you'll get a bad air leak, horrible clatter with the motor running, decel popping like crazy, and unfiltered air entering the motor.
The screw (#1) is what holds it altogether but it is flared on the end so you can't just unscrew it. You can take a grinder or dremel tool and grind the flare off and then unscrew it, but if you slip and knick the gasket you'll have a leak. I recommend just taking a pair of pliers and pulling off the #2 and #3 plates, you can bend them, they will snap right off and the screw will come out as well. It destroys the #2 and #3 plates but we're not reinstalling them anyway and it's MUCH faster than hassling with the screws. Another option is to drill the screw out on a drill press using a 7/64" bit, this idea was presented to me by ISKIVT of the VTXOA.

I do want to offer this word of warning since it was mentioned to me by one rider... He broke the gasket plate itself in half when trying to remove parts #2 and #3 from #4. First, be careful - it doesn't take a lot of force just a good pair of pliers and a few times bending and "rocking" the metal back and forth to snap it off. If you do have the misfortune of breaking a plate, don't panic! You can use a small dab of JB Weld CAREFULLY applied to put it back together and use some high temp RTV to seal the block-off plate. To be honest, if you use the hight temp RTV you don't need the gasket plate at all, but I like to keep it in for good measure (between the gasket and the RTV you have 2 seals so you're sure not to get any leaks).

With #4 separated from #1, #2 and #3 drop #4 back in the reed hole on the motor where it came from and install one of the block-off plates back on top of it. Some folks like to put a bead of RTV silicone (high temp variety) on the plate before you put it on, I have never done this and I have never had a leak - BUT it is a very good idea that only takes a moment and helps ensure a good job (I would use it but I just never have any around when I need it, lol).
With the gasket plate (#4) back in place install the block-off plate using the same 8mm bolts that were used to hold the reed valve in place. There is no specific torque spec for these bolts in the manual but trust me, they are small enough that you don't have to really "wrench" them down tight. Get them snug and you can leave them alone. This is what you will have:

I know that's the front plate installed, but you get the idea.
Now reinstall the rear coil, spacers, bolts, wiring, etc.

With the back PAIR valve done we'll move to the front one. You can "center" the tank back on the bike and slide it backwards to get clearance to this one. It is on the front left of the motor and like the back one I find it easiest to get to the right bolt from the right side of the bike (reaching across the motor) and the left bolt from the left side, lifting the top radiator hose to get to it.

Use the 8mm or 5/16" wrench to remove the bolts and remove the reed valve and gasket plate assembly just like on the back one. Disassemble the gasket plate just like the other:

Remove 1, 2, and 3 and reinstall 4. Put the block-off plate on in place of the reed valve using some high temp RTV if you choose to. Reinstall the 8mm bolts and snug them down. When working on this be careful as I don't think I've ever done a desmog where I didn't drop one of the 8mm bolts and end up spending some time scouring in the radiator/fan area to find it. One of those telescoping magnets helps a lot if you drop the bolt. Here's the completed product again:

At this time if you're on a 49 state (non CA) bike you are done and you can skip down to the "reassembly" section and put everything back together.

CA model additional steps
Since I have a 49 state bike I can't comment too accurately on the following steps but Paul (Rev on the CA forums) was nice enough to detail the process with some pics on an 04 1800 N model.

Look under the bike near the rear tire, that "soup can" you see is the evap canister. Remove the two 10mm bolts and remove the canister. The small hose is from the fuel tank and is to be routed down the side of the coolant overflow tank, the other lines will come out with the evap canister.

On top of the intake manifold behind the throttle body you’ll see a 1/8" black hose that forms a "T" with two ends plugged into the rear of the intake manifold and the other end routed to the evap purge control solenoid. Remove the 1/8" rubber hose "T" ends from the rear of the intake manifold brass nipples and replace them with the last two 1/8" rubber caps. Now follow this line to the evap purge control solenoid.

Here is the hardest part of this entire job, the control valve. On the right side of the bike behind the rear cylinder you can get to the first bolt with a 10mm open end wrench just behind the exhaust pipe. If you can't get a tool onto the upper bolt from the right side try the left side (even though it's a tight fit and you have to squeeze the extension through several lines).

The bottom bolt is easy once you remove the ignition switch - it's only held in by two screws so this part is simple.

Once the two bolts are out and the electrical connector is unplugged, pull the control valve out with all the hoses attached.

The hose from the left side of the fuel tank is routed down the side of the coolant tank. If need be you can use a few zip ties to hold it in place.

Reassembly
Reinstall the airbox in reverse order, make sure to plug the crankcase breather back in and the electrical connector for the IAT sensor. Ensure that the 1/2" plug is still in place over where the PAIR hose used to plug in. Get the airbox in place and use a good phillips head screwdriver to reinstall the velocity stacks good and snug - do NOT use the impact driver to reinstall these. Reinstall the filter and the cover with the 5 5mm bolts making sure that you don't lose the 5 plastic washers on these screws in the process.

With the airbox in place check under the left side of the fuel tank to make sure that the 1/8" tank vent hose is still on before sliding the fuel tank in place, it usually gets pulled off when you slide the tank back. Slide the tank forward and into place making sure you catch the rubber "bushings" that it snugs into in the front. Reinstall the 10mm bolt that holds the base of the tank in place.
Pick up the dash, unwrap it from the towel, and make sure that the little rubber cover is still on the tab on the front of the tank where the dash slides on. Remove the gas cap, slide the dash into place and reinstall the gas cap.

Remember to leave the gas cap on when working with the
screws for the dash so that you don't drop the screws IN the gas tank!
Reinstall the 3 5mm dash screws complete with plastic washers:

And reinstall your seat:

That's it - you're done - congratulations!

Afterthoughts
This is an inexpensive mod that helps cut down on about 95% of the decel popping this bike is famous for. It will help stop the "blatty" sound you hear when you first start the bike when it's cold and it will make your exhaust note a little deeper. It will not have ANY affect on the performance of the bike and doing it requires no additional "mapping" changes to your fuel manager. Some have argued that removing the smog system from the bike may aid exhaust scavenging when using a 2-into-1 or a 2-into-2 exhaust with a crossover. While this is likely true (the smog system would tend to cancel out scavenging effects) the results would be, in my opinion, very minimal and not worth mentioning.

A lot of people ask about the warranty aspect of doing this mod. The bottom line is that it will depend on your dealer and how much of a pain they want to be. Technically they cannot refuse you warranty service based on this mod, but some will because - well because many dealers are a pain in the ass. So they may give you grief over it, but if you call Honda of America (bypassing the dealer) they should make them honor the warranty.
The Magnuson-Moss Warranty Act is a vehicle warranty law - US Code - Title 15, Chapter 50, Sections 2301-2312 states "Legally, a vehicle manufacturer cannot void the warranty on a vehicle due to an aftermarket part unless they can prove that the aftermarket part caused or contributed to the failure in the vehicle." This means that if a dealer tries to void your warranty based on modification to the vehicle then they have to prove (They have to prove, not you) that the problem you're having was caused by the mod you did. Since the desmog (when done properly) cannot cause problems on the bike they would be forced to honor the warranty.