Crankcase vent using a reed valve.

gggGary

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You may not have this issue but the crankcase vent tends to do a rather poor job of keeping the oil inside the motor. Yamaha tried MANY variations through the years, none were a true Silver bullet solution.
A reed valve CCV system seems like a very good idea on any 360 parallel twin. Running a slight vacuum in the crank has some advantages;
lower pumping looses it takes power to run what is basically an unused air compressor.
negative pressure should help reduce oil leaking from engine seals, gaskets etc.
Norton guyz have the same issues we do, maybe a even worse with a "dry" sump and remote oil tank. They have some reed valve type set ups offered by the vendors, at rather high price points. They did did some studies and found reed valves will hold a slight crankcase vacuum up to about 4-5000 RPM, after that effectiveness tapers off, prolly about the max speed of the reed valves being able to act as a one way seal. Below 5K RPM prolly covers about 98% of all engine operation for the typical rider.
So the ole skin flint wants to try this and was thinking on lower cost alternatives. Then @Mailman mentioned this one is available.

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I gotta say this looks rather sweet, compact, easy, just pay n go. But that's no fun?
So a bit of searching on Fleabay
first look was a reed valve for a small 2 stroke.

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was a bit big for this use, an intake reed valve housing tends to be constructed "backward" for our CCV use.
Then I found that many motorcycle use a pollution reduction system with reed valves in housings.
Found a couple set ups so cheap, they are on the way here.
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This octopus from a gixxer to my door for $4! Worth it just for hoses and clamps? Obviously bike wreckers can't GIVE away these systems.
this from a GS500 might be a bit more plug n play.
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These systems use a vacuum solenoid to open and close the air passage depending on intake vacuum which we shouldn't really need/want for a CCV so will look into removing that. There's another wrinkle on oil in the vented air stream, I haven't seen explored, I will look into that also.
That's where I'm at for now.
 
On going madness?
yeah that sums it up pretty well.
But yes madness needs a bit of help in the CCV system.
 
Any horsepower gains should be viewed with a jaundiced eye.
The Harley guys deal with the same issues, Grizzly's valve is typically sold to that crowd...
This guy did a bunch of dyno testing;
http://www.nightrider.com/biketech/crankvent_test.htm
Apparently Harley uses an active "umbrella valve" crank vent on some of it's motors.
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Very simple one way valve.....
 
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https://www.mikesxs.net/yamaha-xs650-reed-type-engine-breather-valve-pcv.html
Your probably know of this simple solution, the MikesXS reed breather. I've been running one of these for probably 10 years, and am satisfied. I use it the same way people use the Dorman Power Brake Check Valve, I.E. attached to the engine breather outlet with a hose, and pointed at my air filter element.
From the site:

Reed type Positive Crankcase Ventilation Valve. Valve hooks to engine top breather vent and allows expelled air out but reed prevents air re-entering quickly so a very small vacuum is created in the crankcase.
 
View attachment 206546
https://www.mikesxs.net/yamaha-xs650-reed-type-engine-breather-valve-pcv.html
Your probably know of this simple solution, the MikesXS reed breather. I've been running one of these for probably 10 years, and am satisfied. I use it the same way people use the Dorman Power Brake Check Valve, I.E. attached to the engine breather outlet with a hose, and pointed at my air filter element.
From the site:

Reed type Positive Crankcase Ventilation Valve. Valve hooks to engine top breather vent and allows expelled air out but reed prevents air re-entering quickly so a very small vacuum is created in the crankcase.
Thanks DB, forgot to add that one, at $35 an attractive price point. Looks to me like they did about what I'm thinking, repurposed an existing reed valve from another application.
 
Oddly Krankvent pushes them for use in 4 cylinders also, which do not have the large crank pressure oscillations that 360 twins (and V twins) do. I guess some blow by CC pressure is common to all motors.

The Norton guys go at it.
https://www.nortonownersclub.org/support/technical-support-commando/crankcase-breathing

The "real" Mike found one also @650trader
https://yamahaxs650.com/product/reed-type-pvc-valve/
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some more reed info
https://www.mikesxs.net/blog/how-to-install-the-pcv-reed-type-valve/
randomly found installed valve.
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More on cross pollination Norton guys buying parts from MikesXS! https://www.accessnorton.com/NortonCommando/xs-type-reed-valve.29838/

Here's one
https://www.ebay.com/itm/362071145936
turns out it's an EGR valve not an PCV valve
 
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