Open up the Exhaust for Increased Performance
The stock KLX250 exhaust system is quite restricted.
Performance can be increased with a better exhaust system.
There are many after market exhaust systems available for the KLX250 however most of them are quite loud.
An alternative is to find a KLX300 exhaust system that will fit on the KLX250 with no modifications.
2000 to 2007 KLX300 mufflers will work on your KLX250 bike.
The KLX300 muffler has a larger inlet than the KLX250.
The KLX300 header pipe is the same diameter as the KLX250 and is necked up to a larger diameter where it connects to the KLX300 muffler.
The parts diagram shown below does not really show the necked up portion of the header pipe, but it is there.
If you look closely at the photo below you can see the diameter increase.
So you cannot install a KLX300 muffler without the KLX300
I was able to find a FSW (Four Stroke Works) header pipe at a reasonable price on e-Bay.
It is the larger diameter from the head to the muffler.
The KLX300 muffler has a removable baffle at the outlet. This can be removed for increased performance and the spark arrestor will still be functional as it's inside the muffler.
I installed an unrestricted end cap on the muffler that I purchased on
In summary you will definitely feel the increase in power by opening up the exhaust on the KLX250.
20000 to 2007 KLX300 Exhaust System