2009 KLX250s Nubie question on KLX300 Exhaust
 

Hey all been lurking for a while since I got my '09 , found an great craigslist deal in NJ this past Nov , supper clean , stock with only 825 miles , purchased for $2,200 , VERY happy with it !

Getting ready to do most recommended mods, I just haven't decided on exhaust yet , I have a complete Two Brothers set up that I will try but I think it may be too loud...

I also have a nice clean 300 muffler but no head pipe for it , has any modified the 250 pipe to work with the 300 muffler ? I have a welding set up and was considering putting larger outlet on end of pipe

Thanks for all the great info here

Save a search on fleabay for the header, they come up every now and then, pretty cheap.
If I find a Four Stroke Works header, I'll sell you mine.
I can also take pics if you want a close up of how Kawi expanded the pipe.
Keep in mind the 300 header has a slightly different shape and length too.

Probably easier to just mod the stock 250 can into a 300 style since the 300 header won't be of any benefit anyway (same diameter just longer) -

KLX World: KLX250S Custom Stock Exhaust Mods

You can build an endcap out of pipe fittings from the hardware store or buy and endcap on ebay -Kawasaki KLX 300 KLX300 Muffler Exhaust 2D Power Tip w Spark Arrestor Screen | eBay

Here's a KLX300 head pipe on e-Bay. The price is ridiculous, but you can see what it looks like and create your own search for a pipe.
It's basically a 250 header pipe that necked up to fit the larger KLX300 muffler.

Exhaust Pipe Header 2005 Kawasaki KLX300 KLX 300 | eBay

Doug

Wow! I paid $65 for a 300 header and an FMF PC4.
Start welding. Might as well order some same sized pipe as the muffler and make your own. Ah, if I had a welding set-up...

Thanks for the Tips , I will explore modifying the stock muffler , I didn't realize the 300 pipe was a different length ,

Thanks for the links !!!!

Since you have a welder, just cut the end off both and weld the 300 end on you stock muffler. You could maybe make the cut far enough forward the number plate would cover the joint. You would get rid of the pea shooter and have the option of removeable end cap.

Edit..2009 side cover does not cover the muffler end very much, hopefully you have mad welding skills.

The difference in length between a KLX250 head pipe and a KLX300 head pipe is minimal if any.

I have installed a KLX300 head pipe and a KLX300 muffler in place of the original KLX250 head pipe and muffler and it fits perfectly without any modification.

So there's really no need to modify anything.

Just find a KLX300 head pipe and use the KLX300 muffler you already have.

How Well Does It Work?
 

Contemplating the same mod. I actually have a HMF exhaust system on now, which came on the bike and delivers a dramatic increase in power, but it is way louder than I'd like. (I also have the original system so I know how quiet it can be.)

I'm toying with the idea of trying a KLX300 system, thinking it might strike a happy medium between noise and power.

So, how does yours work for you? How is the power and noise level compared to stock or 3rd party slip-ons?

Help appreciated.

With the KLX300 exhaust the power is definitely up.
BTW I'm using a FSW header pipe I found on e-bay in place of the smaller in diameter KLX300 header pipe.
Can't compare the power level to an aftermarket system since I've never had an aftermarket system on the bike.

The noise level is louder than a stock system but not as loud as most aftermarket exhaust systems.

With lower gearing, a pumper carb properly jetted, the KLX300 exhaust, and a KLX300 cylinder and piston the bike is a pleasure to ride. It's a totally different package than a stock KLX250S.

hope this helps some