[RPyfz450]

When you remove the spark arrestor from the YFZ450's muffler, is that all you do? Do you put something back in it's place?

 

[seatec]

As i underatsnd it no. YOu just leave the end open which allows for the beter airflow. The next step on your part should be to rejet and take the airbox lid off.
that will make your bike feel much more responsive.

 

[yfzonly.com]

It's that simple, just take it out and leave it out.