Most new Hondas (and other new motorcycles) are equipped with a PAIR or secondary air system. PAIR stands for Pulsed Air injection. It is sometimes also referred to as a smog pump. The purpose of this device is to burn off unburned hydrocarbons in the exhaust in order to meet emissions requirements. They typically only operate during high-vaccuum conditions and work by drawing filtered air from the airbox and pulsing it into the exhaust port. On closed-throttle decelleration the PAIR system can usually be heard popping... it sounds like a backfire. Here's a basic diagram from the repair manual:
I like to remove this equipment for a few reasons:
1. I don't think it's neccessary. I'd be willing to debate its pollution-fighting merits if anyone cares but I'll spare you the rant for now
2. Removing the system eliminates a lot of clutter in the engine bay, making maintenance easier.
3. Dyno tuning becomes simpler, as the system confuses the tuner's "sniffer" that measures the air/fuel ratio.
4. It's fun to take apart motorcycles and put them back together. :) Especially Hondas.
Here's how it went. First I lift the tank and support it with a strap:
Next I take off the airbox cover.
This is all the crap (bugs mainly) that came out of the air filter when I banged it on the floor:
Top view of the inside of the airbox. The layout of the throttles repeats the offest layout of the cylinders with their growly firing order.
There is a little hole in the side of the airbox where the PAIR draws air in.
From the outside: this is the suction line that feeds the PAIR
Bottom of the airbox and ECU removed:
The 2 silver pods with hoses attached are the PAIR valves for the rear cylinders
To get to the front cylinders I had to remove this engine shield that sits over top of the cam cover. The manual says to remove the throttle bodies to get this out but I didn't want to go that far. A bit of wrangling and some skinned knuckles and I popped it out:
Here are the front PAIR ports, housed in one double-sized pod: (look next to the hose and hose clamp)
Rear cylinder head with PAIR valves removed and the holes left behind:
The holes need to be covered up, as they drop right down into the combustion chamber. A "block off kit" is needed. There won't be much of a demand for kits for the VFR (typically this mod is only performed on race bikes or heavily tuned bikes) but I studied some parts diagrams and found that all recent Honda sportbikes use 1 of 2 different valve assemblies. Multi cylinder heads (CBRs) use a pair of twin-port units while single cylinder heads (RC51) use a single valve unit. I contacted Kyle Racing and ordered a CBR kit and a RC51 unit. Here are the plates, machined out of aluminum and anodized in black:
I spread on a very thin layer of gasket maker and slapped them in place. I was careful not to over-torque (and thereby ruin a cam cover)
This mod doesn't increase performance, but it gets rid of a lot of bulky unneccessary junk and it gave me a good excuse to dig into the guts of the bike and learn how it all goes together.