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Exhaust Back Pressure

Discussion in 'Motorcycle Tech Talk' started by Frank Lorbach, Oct 2, 2022.

  1. Frank Lorbach

    Frank Lorbach Member

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    I recently finished rebuilding a 84" panhead with a CV carburetor and stock ignition system of points and condenser. At the time of start up I had a free flowing exhaust system on it. Since then putting on 600 trouble free miles. Over the winter I installed a replica stock exhaust system that is considerably quieter than the previous exhaust set up. As it stands now, it pops when cold, stalls out at a stop and it stubborn to restart when stalled. My question is, do I need to rejet the carb because of the increased back pressure?
  2. Frank Lorbach

    Frank Lorbach Member

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    Here is some additional information that I left out from my earlier post. The size of the main jet is 180 and the pilot is 46.
  3. Red Rider

    Red Rider Well-Known Member

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    Symptoms don't sound like an exhaust problem, more like a carb problem, but not jetting size - more like a vacuum leak or clogged jet. If it sat for a seas0n after 600 good miles, maybe the tank dropped some 30 year old gunk into your carb. Seen that before. Good luck!
  4. Frank Lorbach

    Frank Lorbach Member

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    Thanks for the reply. It wasn't an intake leak. I checked that with an unlit propane torch. I found some sediment in the flow bowl which took me to the pilot jet and main removal. I got cleaned everything and buttoned up. First kick , no popping. Let it get to temp and shut it down to re-start, one kick. Amazing what a tiny piece of crud can do to ruin the day.

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