So part of this weekend's project was to remove the Kawasaki Clean Air (KCA) system from the bike. In more modern terms, this device is known as secondary air injection.
The purpose of KCA is to inject extra air into the exhaust system just after the exhaust valves to help burn any unburned fuel that made it out of the cylinders. This has the effect of reducing the emission of unburned hydrocarbons as well as facilitating the conversion of carbon monoxide in the exhaust into carbon dioxide.
This air injection is accomplished by means of a vacuum switch valve which is perched atop the valve cover. Vacuum is teed in to the carbs and a large hose carries filtered air from the airbox through the valve and to ports at the front of the cylinder head. Under the ports are reed valves which open in response to pressure fluctuations in the exhaust and admit fresh air to the exhaust to facilitate continued combustion. The reed valves admit air flow only one way so that exhaust gases can't be forced back upstream into the system.
"This all sounds great" you say, "so why disable it?"
First reason to disable it is that this system is responsible for the annoying popping you get through the exhaust on closed-throttle deceleration. The second reason is that if it stops functioning properly, it can cause driveability problems such as inability to obtain stable idle, greatly reduced engine power, or abnormal engine noise (these are all quoted from the W650 owner's manual). So being in favor of more simplicity and less complexity, I elected to remove the system.
To Kawasaki's credit, this system is nicely designed as a totally passive system with no electrical or other moving parts. It works purely on vacuum and fluctuating air pressure. That said, removing it means one less thing to go wrong and helps clean up the look of the bike a bit as well.
Not all W650s were fitted with this system, which means that parts are available from Kawasaki to convert the bike. Someone posted the following parts list somewhere and I'm sorry but I don't remember who to give credit to. You will need:
Kawasaki p/n 11060-1886. You need 2 of these - gaskets (if you don't buy the shorter screws below, you'll need 4).
Kawasaki p/n 11065-1135. You need two of these - these are the replacement injection port covers without the fittings for the air injection.
Kawasaki p/n 92005-1017. One of these. This is a 3-way vacuum fitting to replace the 4-way fitting under the tank.
Kawasaki p/n 92066-1389. One of these. This is the plug that fills the hole in the airbox for the pipe that runs to the KCA vacuum valve.
Kawasaki p/n 92150-3775. Four of these. These are the bolts that secure the port covers to the cylinder head. They are 6x18 while the USA versions are 6x22.
These are obviously non-US parts so I don't know if you can get them from a US Kawasaki dealer. I bought them from CMSNL
in the Netherlands.
Part number searches on U.S. retailer websites have identified the following parts are available as U.S. parts - presumably they are used on other U.S. Kawasaki models:
92150-3775 - bolts
11060-1886 - gaskets
92066-1389 - plug
92005-1017 - vacuum T fitting
So it looks like the only parts you have to buy with the Euro are the port covers.
Removing the system is pretty straightforward. First, remove the seat, tank, and left side cover:
Then on top of the valve cover, you see this guy:
Disconnect the hoses that go from the vacuum switch valve to the ports at the head, to the 4-way vacuum tee, and to the pipe from the airbox.
Pull the pipe straight up out of the airbox and then remove the grommet from the hole. Replace the grommet with the plug.
Remove the vacuum switch valve; nothing holds it in place.
Remove the 4-way vacuum tee with hoses attached from the carbs. Take the hoses off the 4-way tee and put them on the 3-way tee, then reinstall.
Get out your 5mm Allen socket and remove the two reed valve caps at the front of the cylinder head.
Be aware when you remove everything, there are two gaskets per side - one on each side of the reed valve. The gaskets may stick to the caps or to the cylinder head. Make sure you have all the gaskets accounted for before you put stuff back together. You should have this:
Now you are ready to reassemble with the new parts. Here is where I ran into a little snag. Whoever provided the parts list for this job neglected to mention that you need four shorter screws if you don't want to re-install the reed valves. The screw holes in the head are only so deep, and if you attempt to re-assemble without the reed valves, the screws will bottom out. Later research has shown that there is a different length screw used on the Japan-spec model without KCA. The part number for the correct screw has been added to the parts list above. Since I didn't have shorter screws and since I didn't have four gaskets, I used my two new gaskets and scrounged the best of the old gaskets for the other two. Then I put the whole thing back together with the reed valves in place but with the new blank caps. Like this:
Torque those bolts to 12Nm only! Don't overtighten!
That's pretty much it. Just slap the tank back on and you're good to go. This is the pile of crap that you have just removed from the bike:
I also replaced the front brake pads with the EBC FA231HH pads. That job was so simple I didn't bother to take pics. Haven't gone for a ride yet on the new pads but I expect them to be an improvement based on my experience with them on my old Triumph Tiger.
2015 EDIT: Addendum to this post here