Best aftermarket slip-on?

If you haven't done the endcap mod mentioned in other posts, I would try that first (it is easy and doesn't cost a thing). I removed the restrictive part of the pipe to the washer and noticed a substantial increase in power without much increase in noise at all. JD jetting's KTM 530 exc went from 37 to 50 hp with this mod and a jetting change. My personal guess is the muffler mod made most of the increase. My FE570s ran cooler as well - it seemed to be on the hot side before.

FMF 4.1 was the way to go for my 570S. Power, quiet and cool.

I debated for over a year before finally spending the money for a new silencer. I don't know that it is the "best", but I am very happy with the FMF 4.1 with quiet/spark arrestor insert. When I pulled it out of the box, I was surprised that I could see right through the thing. I couldn't imagine how it could muffle anything since it was a straight shot right through the can. With the quiet insert, you can't see through it any longer, but it still seems to flow much better than stock. And I was surprised that the sound is not bad. I expected it to be too loud, but it is barely louder than stock. I don't find it obnoxious at all, and I don't like loud bikes. The bike runs cooler, and it shaved about 1.2 lbs off.

But note that FMF sells a quiet insert, a spark arrestor insert, and a combo quiet/spark arrestor insert. I wanted the combo insert.

Hey DeeG,
Was there any particular reason/s you went with the FMF over the Akrapovic?
Regards,
Davo.

I can tell you in 3 words why I chose FMF over Akro.

1. Money.
2. Money.
3. Money.

Electrified said:

I can tell you in 3 words why I chose FMF over Akro.

1. Money.
2. Money.
3. Money.

Click to expand...

I knew that one already :lol:

I have an akra on my 570 and its awesome with out the db restricter, build qual is great and sounds nuts, dont get it if you like a quiet bike as the db insert kills the performance

Davo said:

Hey DeeG,
Was there any particular reason/s you went with the FMF over the Akrapovic?
Regards,
Davo.

Click to expand...

Electrified called it - money. From YouTube videos I like the sound of the Adrapovic, but it is way more expensive in the US.

Tariff on titanium imports into the US drives the price up is what I heard.

I have the Akrapovic on my 450 and it sounds great, but definitely gets loud at higher rpms.
At idle it is about 94db and starts barking in the midrange!

I am thinking of the FMF megabomb header to go with it, because the Akra header is too expensive here.
The header quiets it down a bit and gives performance gains.

I went with the FMF Factory 4.1 on my 570 and didn't buy the megabomb. I run it with the spark arrester, and it has an impressive growl and it's definately not too loud. It's jail bait without the spark arrester, but it's fine with it.