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techtalk:ref:carb06 [2019/06/26 17:13]
hippysmack [Running the Breather Hoses] 		techtalk:ref:carb06 [2019/06/26 17:27]
hippysmack [Running the Breather Hoses (91 and UP)]
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 ====== Running the Breather Hoses (91 and UP) ====== ====== Running the Breather Hoses (91 and UP) ======
 +===== How the umbrella (breather) valves work =====
 +Read more about the breather valve system here: [[techtalk:​evo:​engmech07|Evo Crankcase Ventilation]]. \\
  
 +The breather valves are located in in the rocker box with their air outlets in the heads. \\
 +The breathers are one-way umbrella valves. \\ 
 +These exit crankcase vapors through vents in the top of the cylinder head into the air cleaner. \\
 +On each piston downstroke, crankcase pressure (air and oil mist) is routed up the pushrod tubes into the rocker box. \\
 +Collected air pressure and oil mist in each rocker box is routed up into a sealed cavity in the lower portion of the box. \\
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 +This mixture passes up from underneath a rubber one-way valve sitting over the cavity inlet in each box. \\
 +The oil is designed to separate from the air by hitting the underside of the umbrella valve and dropping back down into the lower end. \\
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 +Air pressure is designed to continue up past the umbrella valve and exit the hole in each head on the intake valve side.
 +Air pressure escapes the head through the hollow bolts (one in each head) that hold the air cleaner mount. \\
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 +{{:​techtalk:​evo:​engmech:​91-03_sportster_head_breathing_2_drawing_by_hippysmack.jpg?​direct&​300|}} ((drawing by Hippysmack)) {{:​techtalk:​evo:​engmech:​04_up_head_breathing_drawing_2_by_hippysmack.jpg?​direct&​300|}} ((photo by Hippysmack))
  
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