I think too much - Breather system question

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06-20-2018, 04:00 PM

aGoodRogering

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I think too much - Breather system question

Sitting at work thinking about my Harley.........because that’s what most of us do, right? And I got to thinking about the breather system and how the downward pressure of the piston creates pressure in the lower end and the pressure needs to be released through the breathers. What I don’t get is, why isn’t the pressure relieved by the opposite piston moving up? Maybe my understanding of the timing is wrong. I’m a computer nerd, not a mechanic.

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06-20-2018, 04:53 PM

Max Headflow

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Pressure is relieved as the pistons go up but air is not allowed to flow back into the motor due to 1 way valves in the heads. (assuming late EVO - UP)

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06-20-2018, 07:21 PM

Ed Ramberger

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Quote:

Originally Posted by aGoodRogering

What I don’t get is, why isn’t the pressure relieved by the opposite piston moving up? Maybe my understanding of the timing is wrong. I’m a computer nerd, not a mechanic.

You're thinking it's like a car crankshaft. Both pistons move up and down together in a Harley.