Velocity stack tuning

• carburetor
• Velocity stacks
• 2007 Honda Shadow Spirit 750

• 

  Nick

  8/16/26, 8:51 AM

  I recently got a velocity stack and tuned the carb as best I could. I think it's running slightly lean but changing the pilot jet up a size makes it run really rich at idle, and it bogs if I move the needle jet up any more as well. I have these marks on the velocity stack screen pictured below. Is this from the carb backfiring? I don't hear any pops except on very hard deceleration/engine braking. Should I be worried? Any advice would be appreciated

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  TJ Admin Staff member

  8/27/26, 6:18 PM

  @Nick if you dont hear a backfire which is a distinctive sneeze, you dont have backfire. the screen marks arent indicative of any issues but it does sound like a vacuum leak could be at play here. 

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