Pair Valve Blockoff Mod

From VFRwiki

A mod that is stated to improve throttle response as well as smooth out the Vtec transition.

Here is how to fix the running issues that VFR800 VTEC.

1 raise fuel tank

2 locate hose that runs from the air box to the PAIR valve

3 Insert a blockage into this pipe. (A large ballbearing is good)

4 Ride bike

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 emmisions. 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 emmisions 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 responce we have all been talking about in this thread. Trust me. Block off the PAIR pipe from the airbox to the PAIR valve and go for a ride. You'll be amazed.

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• Pair Valve Blockoff