Pair valve is a pollution reduction device as well, with the sole purpose of adding air to the exhaust to aid in burning unburned hydrocarbons. They've been used on bikes for decades to help meet pollution standards, before bikes ever ran cat convertors. Removing the pair valve and blocking the port off will not add any performance and definitely will add to unburned hydrocarbons. This can be a problem if you happen to live in an area where there are e-checks for registration or if you prefer to keep pollution to a minimum and figure a few ounces isn't worth it.

 

It is only for heating the catalyst. It is a must to get around this issue https://en.wikipedia.org/wiki/Cataly...nverter#Damage
It really does not reduce the power, but it is better to remove it if there is no catalyst - just to overheat the exhaust pipe less at low speeds. You will laugh - my license plate burned so badly. If the catalyst is installed, in no case should PAIR be turned off.

The catalyst is directly involved in the "afterburning". There, in addition to hydrocarbons, work is also underway with a number of exhaust gases, with which nothing can be done simply by introducing air.

 

When you deactivate the O2 sensor you "turn off" closed loop operations. All fueling becomes open loop. This should NEVER be done unless accompanied by a tuning device (EJK or PCFC) that has been configured correctly for controlling the "now deactivated" closed loop area of engine operations.

Simply deactivating the O2 sensor is playing with fire as the stock ECM programming was never intended to use open loop functioning to control the (deactivated) closed loop ops.

Only someone that does not understand the intricacies of EFI ( closed and open loop fuel management ) would "jack around" with their O2 sensor - and doing so likely from listening to other idiots..

Any EFI KLX exhaust system will need to have, or be fitted with, a 12mm (NB O2 sensor) bung in the stock location as O2 deleting components are now (USA), or soon to be, illegal worldwide.

 

You are damn right. Without a wideband O2 sensor to mixture setup with EJK/PC or an extremely known how the engine works, change fuel mixture is a sure way to kill the engine. Too lean - overheating or detonation. Too rich - wash off the honing oil. Also O2 delete illegal in europe more than 5 years.

 

But he also says:
"There is a further restriction in that the engine is limited to 6500 RPM in the top three gears. This is easily overcome by joining two wires together and then the engine will rev out in every gear."

WTF is that about?

 

This is in reference to the clutch switch mod. It bypasses the switch; so, in return, the bike will crank over even with the clutch out. I did this mod, in hopes that my KLX was being limited up top by said clutch switch, like the gentleman said in the article. I had my bike dynoed again, and it did not seem to do anything powerwise. Keep in mind, this is with the US 2018+ KLX250.

 

So the clutch switch mod doesn't actually do anything afterall? I have a stock 2019 that I want to run lidless, FMF slip-on, and probably MCM as well, and I'm a little lost about the fuel tuning. I'd like to eliminate the dropoff in power at high RPM but is that correctable with either the PCFC or PCV? Does the PCV actually allow for ignition timing changes with our bikes? Also it looks like the PCFC allows for downloaded maps, but do those maps allow for ignition timing too (if possible)?

 

Would you need a wideband 02 sensor to use a PCV effectively?

 

It does. It disables the RPM restrictions in higher gears. Tested on my klx, without the mod the max rpm was 7500, and my max speed 114 km/h.
With the switch mod, the max rpm was around 11000 ( or 10000, dont remember well), and my max speed 131 km/h.

IMO, this is a useful mod.

 

By your use of km/h I assume you're in Europe? Are you measuring speed here by GPS or are you talking about what's displayed on the speedometer? My US spec bike has hit an indicated 88 mph before which is about 142 km/h and that's with zero mods except a 13T front sprocket. Are the North American bikes not limited, like perhaps this is a Euro3 emissions thing?