The Honda VFR is a beautiful machine, but its full potential has sadly been restricted to comply with different laws and regulations. There are fortunately some easy steps you can take to remove these limitations and get the full potential of the 800cc V4 engine.
All the mods are easy to do, and are fully reversible in case you want to restore everything to its original state. Please note that you are doing this at your own risk! Many VFR riders have however done these mods without any complications. The description and images are compatible with the 6th generation VFR, them being from 2002 to present date.
First things first. You will need to find the fuel tank. Ready? Okay, now locate the two screws on the front end of the tank and unscrew them.
Now lift the tank up slowly and make sure that the fuel lines or anything else is not stuck.
Make sure to put something sturdy between the bike and tank to hold it up properly. This is of course much easier if the tank is almost empty, so take a long drive to empty the tank beforehand if you want!
We'll start out with a quote describing exactly what the PAIR valve does. If you know where this was taken from, please contact me and I will of course link there.
What is happening is that when the bike is running, the pair is opening to blast fresh air into the exhaust system. This was done to clean up the bikes emissions. This systems worked fine on all models. Even carb models have this system fitted. When the VFR went to the first fuel injected model the PAIR valve was still used again to clean up emissions without any problems. Then the VTEC model came along and it all went wrong. The reason for this is that the VTEC model had an O2 sensor fitted in the exhaust. What happens is that the PAIR valve is working pretty much from idle speed blasting fresh air into the exhaust system. The fresh air entering the exhaust is picked up by the O2 sensor which then thinks the bike is running lean (around 19:1) so sends a signal to the ECU to richen up the fuel mixture. The ECU is now pouring as much fuel into the engine as it can because the O2 sensor thinks its still running lean. The real fuel/air ratio being poured into the bike is now around 11:1 making the bike hard to ride and resulting in the snatchy throttle response we have all been talking about.
So what we want to do is to disable the PAIR valve altogether and the easiest way to do exactly this is to remove the cable controlling it! If you look on the right side of the bike under the very tank you just lifted, you will see cables and a connector like this.
Now just unplug those connectors and use some electrical tape to make sure that no moisture gets into the open ends.
Yes, that's it! You have now successfully disable the PAIR valve from screwing with your O2 sensors. But why stop there...
The air intake box is located directly under the fuel tank and you probably noticed the strange little valve on the top right when you lifted the fuel tank for the first time. Its sole purpose is to strange your VFR! That's right, it limits the airflow at certain RPM's to comply with regulations regarding emissions and sound. This is also know as the infamous flat spot around 5000 RPM.
It is however very easy to disable it. Just pull out the vacuum tube coming out of it and plug it with a plastic plug or similar. Do the same with the valve itself to protect against dirt finding its way in.
Make sure to secure the tube with some tape to keep it from slipping out while riding.
Yes, you read that correctly. You beloved VFR has a snorkel and it has a hard time breathing through it. Just imagine going out running and only breathing through a straw in your mouth. Not a pretty sight.
The snorkel on your VFR is located on the front of the air intake box and it is made of soft plastic, so it is easy to just pull it out without even opening the air box!
Now your VFR finally has the ability to breathe properly, and it will behave much better at high RPM! Just be sure to save it if you want to be able to restore everything to its original state.
You will probably need to open the air intake box if you want to restore it.
I really don't want to write anything here, but instead let you find out for yourself! I am sure that you will be amazed by what your VFR can do now. If this was not for you however, simply restore all mods, which should be very easy if you followed the instructions above.
Okay, if you really want to know the results, here goes. It's a completely new bike! Gone are the hesitations on low RPMs and the flat spot around 5000 is gone, and the engine feels much more responsive at high RPMs! In addition to all this, it runs much smoother overall and has a more distinct and "meaty" sound to it. I have the Devil Magnum Carbon slip-on, which helps.