here's the deal-FUCK 'EM, you don't need them.
Fuk'em only if you know some theory... Whack the crap theory. Here is my 2-bird kill with carb and pipe.
Carb first. Look at my low speed screw position. If I am on the air cleaner side I am an air screw. If I am on the head side, I am a gas needle. Air cleaner side, I can only close air to begin with. Now I can walk up to any carb, know my gas from air screw... Air is how much I set the bubbles to break apart the gas droplets. Gas side, I am letting in the gas via a faucet.
Pipe and pop goes the Penultimate. When I have the bike sitting in the garage, what is the pressure inside the pipe? 14.7 psi/1 atmosphere = The Penultimate Number. Without this number connecting the dots you are fuked with every diagnostic move is a lot of guessing, unless you place the Penultimate front and center.
When I WOT the throttle and lift, what is the backpressure number? What number is heading back into the end of that pipe? 14.7 Penultimate Says I. So you have to ask the 2 killer bird question, did we bang cold into hot? Is supersonic the bang, or did those muffler spacers sort of slowed down the sonic? Straight in is super, you still hear the pop so sonic is still the wave thru the spacers, yes?
So cold vs. hot is even money, right? Now add fuel like the pwcomder says is fill the first two lines so this richens the lean on lift. Now you add oxygen is backpressure heading back in, and this more or less, chemically heats up the cold air is it keeps lighting off with the oxygen entering - as subtle pop.
Two riding thoughts.
1. Theory wise, I understand air is pop is a thunder cloud effect inside the pipe, means cold meets hot.
2. Novice wise, whaaaaa, my pop is I need to waste more gas, I already have the correct amount of gas entering, but I want to keep wasting gas is that pop needs to shut up?
Who's crying? There's no crying in loud bike is my ride.