Originally Posted by Michael Sevostyanov
Emissions related. Connects to the reed valves. It’s whats removed or blocked off when the marbling or coastering mod is performed. That is the primary reason your bike pops when decelerating.
1) is it very important?
2) can it be removed?
Is it important? No not really, but there is one on each cylinder. It can be removed but the ports on the engine that they’re connected to need to be covered with a what they call a “coaster”, you can’t just leave it open.