yoshimura insert?

[jgodfrey]

2011 crf250r which insert should I use? With no other mods or remap.

[rpxtreme03]

If u don't have to pass sound spec the 99db insert is going to be most power

Don't just remove the insert. Ull lose low end

[rpxtreme03]

The part number is # ins-10-k. This is not actually a 99db insert. It's the 99 dB insert in the 09-10 crf450r the 250 is not capable of producing 99db with that ex. So they don't list it as such on the 250. But when I called them they told me if I don't have to worry about sound spec then run that insert it will be about 97 dB bur produces the most power the muffler with no insert at all losses bottom end because it is to free flowing and loses what they call back pressure but us intelligent minded know that back pressure is a myth and the best explanation is that the pipe with no insert is actually losing air velocity

Edited March 31, 2015 by rpxtreme03

[rpxtreme03]

The air velocity is important because like any moving object air when moving will create vacuum. The faster it moves the more vacuum it produces to help pull the air behind it.the trick is to find the balance between vacuum and volume to much volume u lose low end too much vacuum u lose top end

[jgodfrey]

I forgot to add, this is a RS4 it came with two inserts. One has a larger diameter than the other, and the smaller diameter one has a screen welded in front. 

[rpxtreme03]

The smaller one is for the 2m max sound spec and the other is for the 94 dB sound spec. The 99 dB insert is less than 30 and we'll worth the money if ur no concerned about sound spec. The 94 dB makes more than the 2 max but there is not icicle difference with the ins10k