It's sad, and a little weird, to see that this exhaust is no longer available for these bikes.

I'm installing BB's 351 kit and will have to re-jet, so I was thinking it would probably be the right time to do exhaust too...

Would it maybe be worth just finding a used KLX300 exhaust for my 2012? I understand that I would need both the pipe and the exhaust to be able to mount it. Are there specific years necessary? I found a full 2021 300 exhaust locally, but am not sure if it would fit.

 

The exhaust should fit, I put a exhaust from a 2022 klx300 on a 2006 klx 250. The only thing I had to do was plug the O2 sensor threaded port.

 

Thanks!

 

Why would you buy exhaust from klx300 dual sport? It will be heavier and hotter (as it has catalytic converter). Header and muffler are the same as on EFI klx250.
Also honestly I can't rationalize cost of FMF pipe. $400 for a muffler?

What are your requirements for a muffler?

 

I agree, $400 for 2HP is ridiculous, although the 2012 also has a cat, so I don't think the weight is an issue.

I'm going to be paying for jetting and tuning when the larger cylinder is installed, so I figured it would be a good time to open up the air pipeline. It's really hard to figure out what would be worth the time and money, especially when the favored option, as far as I can tell, is no longer available.

My goal for the exhaust is to open up some midrange and give the bike its best breathability.

I have read a lot of posts that mention that with the tip removed the KLX300 exhaust is freer-breathing than the 250, but after more reading this morning, I think that's only with an aftermarket header. So maybe that's the best option?

To some people it's stupid to put a lot of money into a little bike like this, but honestly this is my favorite bike, I plan to use it to do the NEBDR this year and several other longer rides over the long-term. It's my only bike now, and I view it more as a platform. I like the weight, I like the ergos, and there's no other bike in this range that I would prefer, so I'm willing to put some money into it.

 

I'm on the same boat mate! It's just I believe FMF charge way too much for what it offers. See my experience below.

I've done this as my first mod to muffler - I've replaced the end tip pipe with larger stainless steel pipe with diameter 25mm (~ 1 inch.) The sound is nicer, but power gain is minimal if any. I think the bottleneck in the OEM exhaust is in catalytic converted. But the sound is really nice - just a bit touch than stock, but I really like the tone.

Then I've made full custom exhaust with larger diameter megabomb-style header. My goals were (sorted by priority)

1. weight reduction (standard muffler weights 5kg!)
2. not loud
3. get some power

On KLX300 with this exhaust I got 1.5-2 hp increase over entire range - see second chart (blue vs red) in my thread. This exhaust with open airbox had 3.5hp gain over modified stock + KDX snorkel. Also this full exhaust weights 3kg (vs 6 kg standard)
Here is how it looks and sounds .

Now I've switched my custom muffler to an OEM muffler from KTM exc-f 350 / Husqvarna FE350. Reason is that it's a bit quieter - something in between standard KLX250 and my custom muffler. It's flowing a bit worse compared to custom muffler though.

PS if you are interested I still have my custom muffler and can sell it cheap. It's already amended to fit standard KLX250/300 header.

 

The FMF powerbomb header is advertised as lowering the exhaust by 1-2db. Along with the two bros M7 w the P1X quiet insert I found the 351klx not being obnoxious at idle, and not outrageously loud around the neighborhood staying off the rev limiter. Tried to upload a sound clip maybe it loaded.

Theres an old Stroker Inc article on the klx300 build up. Larry Roessler mentions that the klx300 header is the exact same as the klx250 header. Having the bigger diameter I D powerbomb header def helps the mid range on my 351klx. Also eliminated the abrupt welds inside the header flange and matched the I D with the cylinder exhaust port.

 

Two brothers is THE MOST loud muffler I have ever heard. Maybe quiet inserts do some magic..