POP­PING THE QUES­TION

Cycle World - - Cw Race Test 2017 Honda Crf450rx - DAVE WIL­SON MCLEAN, VA

Q:In Don Canet’s piece on af­ter­mar­ket slip-on muf­flers (Eval­u­a­tion, “Yoshimura Sig­na­ture Se­ries Al­pha Slip-on,” Jan./feb.), he men­tions: “…the an­noy­ing de­cel­er­a­tion pop­ping sound that can oc­cur af­ter mod­i­fy­ing a bike’s ex­haust.” What ac­tu­ally causes this? Is it be­cause there is a leak? Even so, what makes the sound? Are the pop­ping sounds minia­ture back­fires?

A:Hey, Dave. Ask ques­tions, don’t an­swer them! Yes, the pop­ping sounds are small “back­fires,” which is re­ally un­con­trolled com­bus­tion that is oc­cur­ring in the ex­haust pipe. Any­thing that re­duces back­pres­sure will al­low this to hap­pen. A crack at the head pipe is the worst.

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