Crankcase venting
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Joined: Sep 2009
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From: deland,florida
Don't need a one way valve,even though I did do the secondary venting on both my street bikes (98" & 124") I pretty much agree with most on here that if everything is done correct,their really not needed
Grand HDF Member
Joined: Sep 2017
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From: Dubuque, IA
No offense but I find that hard to believe. Hence my question above. If you randomly did that on an evo with no one way valve you wouldn't have a gasket that wasn't leaking.
Guess I'm going to have to figure out for myself just what's different cuz there's no way I'm pumping excess air IN and added crankcase pressure. The flimsy stock umbrellas let enough in before they close and the pistons don't need any help creating it.
Be curious to see what your oil tank looked like in the way of air bubbles to see if scavenging is being affected.
Guess I'll have to make a slack tube tester. Appears to be a lot of guessing, hit and miss going on. No one seems to have any answers and it's a science that can have adverse effects on oiling/scavenging.
I know I'm not the only one that's noticed the different sized holes in the breather bolts. Stock 1200s the inside hole is 1/16".
The only way I'm comfortable increasing breathing at this point is bolts with bigger holes and a better one way than the umbrellas that won't let any air in on upstroke like the umbrellas do.
Optimally you want a slight negative pressure under the pistons. Pressure there causes them to work harder and causes ring flutter.
Last edited by 60Gunner; Jul 31, 2020 at 08:35 AM.
Road Captain
Joined: Jan 2009
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On my street bike, I run breathers out of both heads at highest point, going to T, then a one way check valve, then to the catch can, which is vented to atmosphere. I got rid of the crossover vent to oil tank line, and instead run a vent line off the dip stick housing, which goes vertically up under my seat. This line has a one way check valve at the end, then also goes goes to a second catch can, which Is vented to atmosphere, and completely hidden. I used to join that oil tank line to the other lines with another T, but I wanted to clean up the left side of the bike so I used the second hidden catch can. Finally, I run a vertical case vent line off the inspection hole, which joins the head breather line, and then meets the one way check valve, before it goes into the catch can. I like to use gravity on all vent lines as much as possible, running to the highest point I can before I send a line downhill.
Works for me, but not a setup for everyone.
Works for me, but not a setup for everyone.
Grand HDF Member
Joined: Sep 2017
Posts: 4,359
Likes: 1,219
From: Dubuque, IA
On my street bike, I run breathers out of both heads at highest point, going to T, then a one way check valve, then to the catch can, which is vented to atmosphere. I got rid of the crossover vent to oil tank line, and instead run a vent line off the dip stick housing, which goes vertically up under my seat. This line has a one way check valve at the end, then also goes goes to a second catch can, which Is vented to atmosphere, and completely hidden. I used to join that oil tank line to the other lines with another T, but I wanted to clean up the left side of the bike so I used the second hidden catch can. Finally, I run a vertical case vent line off the inspection hole, which joins the head breather line, and then meets the one way check valve, before it goes into the catch can. I like to use gravity on all vent lines as much as possible, running to the highest point I can before I send a line downhill.
Works for me, but not a setup for everyone.
Works for me, but not a setup for everyone.
Anyway. It's everyone for themselves when it comes to crankcase breathing I guess because I can tell there isn't much for knowledge on the subject and a whole lotta hit and miss or just putting up with the **** poor stock setup.
The dipstick breathers are lame imo but if it floats your boat.
Surprised no one here has thought of running it into the exhaust tho instead of the catch can thing. I know a few that have done it. Weld a fitting to a head pipe.
or into the frame.
Last edited by 60Gunner; Jul 31, 2020 at 02:54 PM.
Road Captain
Joined: Jan 2009
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A reed valve like this is the way to go. Thread that in the front edge of the cam cover. Or better yet, the case. Baffle it from oil like I did inside my cam cover and you don't get oil mist carried out.
Anyway. It's everyone for themselves when it comes to crankcase breathing I guess because I can tell there isn't much for knowledge on the subject and a whole lotta hit and miss or just putting up with the **** poor stock setup.
The dipstick breathers are lame imo but if it floats your boat.
Surprised no one here has thought of running it into the exhaust tho instead of the catch can thing. I know a few that have done it. Weld a fitting to a head pipe.
or into the frame.
Anyway. It's everyone for themselves when it comes to crankcase breathing I guess because I can tell there isn't much for knowledge on the subject and a whole lotta hit and miss or just putting up with the **** poor stock setup.
The dipstick breathers are lame imo but if it floats your boat.
Surprised no one here has thought of running it into the exhaust tho instead of the catch can thing. I know a few that have done it. Weld a fitting to a head pipe.
or into the frame.
I run simple, one way check valves and I have run oil baffles (used steel wool type mesh, and other set ups to reduce blow by mist, but my current set up uses vertical vent lines and the way my set up breathes, I have no need for any baffling, other than my oil tank, which is baffled for oil slosh integrity under acceleration, and foam baffles in carb bowls for consistent fuel delivery as well.
As far as dipstick breathers, I’ve vented my Evo FXR oil tank with a one way check valve (tapped into the actual dipstick), and now my twin cam FL style tank. Have used this set up for 15 years now-with tons of testing and finding out what works and what doesn’t for my application. My motor and the way it is used for a street bike is not typical-and neither is my set up. Just sayin’ what works for me after more than a decade of hard core testing. As far as the catch can, if your system is set up correctly for your specific motor and application, you should get little to nothing more than mist in them-no matter how hard your motor works.
Last edited by PWMORRIS; Jul 31, 2020 at 04:03 PM.
Grand HDF Member
Joined: Sep 2017
Posts: 4,359
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From: Dubuque, IA
Spoiler
Wonder if anyone has run this S&S Reed Valve that goes over the end of the pinion shaft. They don't work on the counterbalanced motors tho. Debating pulling my heads this week while I'm off, cleaning them up, and putting the .030 head gasket in or waiting til September/October when Hammer slows down briefly and have them do their Smash Headwork and 107" Kit. Made me a good offer that's hard to pass on and working over the 50mm throttle body thrown in. But I need all this like...well you know. I don't. lol
Either way I want to address this issue before it's a problem and not put the new umbrellas in on reinstall. As it is, the only decent option I really see is the KVP-12 from Hayden. Just not sure where to run it on these twin cams except off the heads. The evo cam covers were much better suited for running it there. Might have to research other options/ locations. Never cared for venting up the same pushrod tubes that oil drains down. Seems problematic by nature. But the heat of the heads is more a problem I think.
Your vertical lines make good sense. The problem some have found with the cheaper one ways or PCVs was they couldn't stand up to the speed at which they open/close on these v-twins and wouldn't last. Especially the spring operated ones. Sounds like you found some that hold up. The Krankvent actually uses the same sized umbrella in a tighter housing and closes instantly on the slightest vacuum.
Reed valves would be ideal tho. Maybe I'll look into inline Reeds. Lot of good ones . Just finding the right one for the application like you said.
Last edited by 60Gunner; Aug 1, 2020 at 01:03 PM.
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