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Crankcase Ventilation is Vital to a 4-stroke engine

1194 Views 16 Replies 5 Participants Last post by  crazypj
I think that about says it all.

Don't be sticking tiny paper air filter pods on your crankcase vent and think that will work, it won't.

If you doubt that then research 'Crankcase Ventilation Pump' and why they even add a vacuum pump on the crankcase of a racing engines.

Why did you post this Trials, everybody knows what happens to a car when the PCV valve is clogged ? <- Because of the pathetic number of motorcycles we see come through here with stupid little paper or felt air filters stuck on the engines. It's like watching lemmings jump off a cliff, it looked like a good idea at the time
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Is that a pair of Murray's carbs on the motor? They have a great reputation for making more power than stock and being easier to tune. if you are worried about the crankcase breather, you might look at building a still air box and venting into that.

And there are no good velocity stacks for Mikuni VM carbs from a gas flow or resonance perspective. Terry Naughton at Hansen Honda had a bunch designed and flow and dyno tested until he finally came up with a design similar to the old Shemozzles used on the works BSA/Triumph triples all those years ago.
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