Breather Question I haven't seen addressed before
#11
How does the exhaust create a vacuum when it's not connected to the intake or crankcase? It's my understanding that the pressure being vented from the crankcase via the breathers is from the pistons moving up and down. The exhaust is pushed out of the combustion chamber when the piston moves into it's up-stroke.
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Gead (04-11-2019)
#12
Any vacuum created by the sweeping of the piston assemblies is countered by "umbrella valves" in the rocker boxes- they are one way valves that only allow air/oil mist to push out- and seal themselves with a hint of vacuum. I also have a SandS reed valve breather gear in my evo that operates the same way.
#17
Amazed how many people don't understand something so simple. The crank case gets pressurized because of combustion gassed getting past the rings (pistons moving up and down is a net zero on pressure and irrelevant). It's vented to the intake so it can be re-burnt inside the cylinder to help with pollution. The vacuum is irrelevant. Venting it to atmosphere is fine (for the bike anyway). Breather systems are valved to help prevent combustible gasses from being pulled into the crankcase.
#20
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SWThomas (04-11-2019)