I use a KLX300 pipe and muffler. The pipe and therefore the muffler inlet are slightly larger than the 250 muffler.

The 300 muffler has a removable tip, unlike the 250 muffler which has the tip welded on. I've never seen the 300 tip. I bought mine used and it came without it. Other than those two things, I think the mufflers are identical. In fact, the muffler is stamped with KLX250 on the ID plate. It has a letter suffix designation that I don't remember. My guess is that it was made for non-US KLX250's

Apparently most people who have the 300 pipe remove the tip and throw it away. The sound coming from my muffler was terrible. It was extremely loud and had a raspy, ugly sound.

The pipe without the tip allowed exhaust to get all over the rear fender. I didn' like that, so I did this:



The unexpected side benefit was that the exhaust was quieted substantially. The sound changed from the raspy, unappealing racket to a throaty thumper sound.

BTW, this is on a 351.

Ron

 

This is where you are drilling the hole. You can see its the spark arrester. It spins the exhaust and the solids go to the out side before they can exit the pipe. The straw is in about an inch or so. Its welded in two layers. I used a 1" hole saw.



I welded in a 3/4" pipe coupling then screwed different lengths of pipe. Once I decided how loud I wanted it, I made a copper tail pipe.



This one was too loud. I ended up with about 4" of pipe. Its still quiet and I doubled the area for exhaust flow. Still have the factory cat.

David

 

Yes! It will improve flow. Maybe not as much as an after market pipe but I could think of a better use for $300.
I cut off the heat shield. Then cut out the spot welds all around the whole can on the end and sliced it open along the seem on the back side. I could then slip out the tip and spark arrestor. I replaced the outlet pipe with a 1" stainless pipe welded on the inside. It sticks out about 1 1/4". Weld it all back up and it looks factory. It MAY be a TINY bit louder but not even noticable. If anything it's a deeper tone.
I did source a good used pipe just in case I messed up or wanted to go back.

 

heres my modded can....

Tip is cut down KFX400 outlet