I just spent some time comparing parts drawings of the '06 KLX250S cylinder head and airbox with those of the '06 KLX300R. Our bikes have an air injection system that's not present on the KLX300 or the older KLX250s. This includes a valve that draws air from the airbox into the exhaust valve area during the exhaust stroke to increase exhaust gas temperature. It's the first thing you rip off a modern Bonneville because it makes the pipes turn blue.

The purpose of the air injection system is only to help pass the EPA. There is also a catalytic converter in the exhaust pipe!

Removing the air injection system won't make a darn bit of difference in how the bike runs but it will lower the temperature of your exhaust pipe a bit if you care about that. Mine's already blued significantly.

 

Todd, are you sure there is not a CAT? The owners manual says it has one. If so, would the cooler exhaust tend to adversely effect the system.

Tony

 

Yes, you're correct. There is a CAT and lower temps would be bad for that. I'd not mess with the air injection unless you change exhaust systems.

I only bring this up so folks will understand why their pipe is bluing so fast underneath the heat shield and for future reference in case you decide to swap out the head and cylinder for those from a 300.

 

The bikes out here in the south pacific dont have the air injection and the pipe doesnt look like it has a cat in it.
Lee

 

I have put a hmf exhaust and rejetted the carb. And i know what he means when he says the pipe gets very hot and tend to pop on decel. If i remove this will it hurt the performance of the bike?

 

My 09 had both the cat and air inject, that exhaust was very hot even 3 or 4 minates after the engine was shut down