Vented dipsticks / crankcase breathers
Thread Starter
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Road Master
Joined: Mar 2020
Posts: 1,078
Likes: 267
From: New England
Vented dipsticks / crankcase breathers
Feuling - $280 - https://www.feulingparts.com/sku/3092
A1 Cycles - $90 - https://www.a1cycles.net/new-product...e-black-finish
What am I missing, why is the Feuling unit triple the price?
A1 Cycles - $90 - https://www.a1cycles.net/new-product...e-black-finish
What am I missing, why is the Feuling unit triple the price?
Thread Starter
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Road Master
Joined: Mar 2020
Posts: 1,078
Likes: 267
From: New England
I noticed that A1 claims a flapper valve is not optimal because you want the motor/crankcase to be able to push and pull air....
Seasoned HDF Member
Joined: May 2008
Posts: 21,174
Likes: 12,744
From: South Carolina
Feuling - $280 - https://www.feulingparts.com/sku/3092
A1 Cycles - $90 - https://www.a1cycles.net/new-product...e-black-finish
What am I missing, why is the Feuling unit triple the price?
A1 Cycles - $90 - https://www.a1cycles.net/new-product...e-black-finish
What am I missing, why is the Feuling unit triple the price?
Junk you don`t need.
Here`s an idea, just use the dipstick that came with the bike and keep the money in your pocket...
Grand HDF Member
Joined: Sep 2017
Posts: 4,359
Likes: 1,219
From: Dubuque, IA
Ideally you want to maintain a slight negative pressure under the pistons. What you dont want is them fighting against pressure on the downstroke and the one way valve is there to expel the pressure they cause on downstroke, then close at the first sign of air being sucked backed in on upstroke.
Last edited by 60Gunner; Nov 5, 2020 at 08:00 PM.
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,925
Likes: 8,027
From: poway
No you dont. Not unless you want to build excessive crankcase pressure. It's also a cause of ring flutter.That's why the stock breathers are one way valves. Not very good ones but then neither are the ones you reference.
Ideally you want to maintain a slight negative pressure under the pistons. What you dont want is them fighting against pressure on the downstroke and the one way valve is there to expel the pressure they cause on downstroke, then close at the first sign of air being sucked backed in on upstroke.
Ideally you want to maintain a slight negative pressure under the pistons. What you dont want is them fighting against pressure on the downstroke and the one way valve is there to expel the pressure they cause on downstroke, then close at the first sign of air being sucked backed in on upstroke.
Went you say fighting against pressure on the down stoke, if the pressure in the cylinder is less than the pressure in the crankcase, won't the motor stop running?
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Road Warrior
Joined: May 2011
Posts: 1,956
Likes: 439
From: florida
Lets all remember how fast these pistons are moving. Any style of venting is just allowing excess pressure out. HD went to a screw in dipstick for the very reason of excess pressure blowing out their older press in dipstick. Big motors create even more in the case. Im not sure which unit is better (one way valve or none) but IIRC Tmans set up drills the fill neck and runs a line wout a valve. As long as you dont hang the vent line out in the wind I would expect youd be just fine but Im no expert
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Grand HDF Member
Joined: Sep 2017
Posts: 4,359
Likes: 1,219
From: Dubuque, IA
Now that's hilarious. First off you don't maintain negative pressure. At near BDC both pistons there is positive pressure or the valve won't do anything.
Went you say fighting against pressure on the down stoke, if the pressure in the cylinder is less than the pressure in the crankcase, won't the motor stop running?
Went you say fighting against pressure on the down stoke, if the pressure in the cylinder is less than the pressure in the crankcase, won't the motor stop running?
I know of a few that have vented into the head pipes using the exhaust pulses to aid in the process.
https://dsportmag.com/the-tech/quick...essure-part-1/
Last edited by 60Gunner; Nov 15, 2020 at 03:08 PM.
Road Captain
Joined: Jan 2009
Posts: 714
Likes: 120
Mine is a twin cam, and TR’s kit is for M8’s, but basically we all run the same venting stuff we learned from land speed hi rpm pressures for extended periods of time, and or, extreme CC pressure in super hi comp drag racing. If you have a stock or near stock bike, simply run a quart low and leave it as it is. All good.
if you have a built motor, higher comp, more cubes, love to spin it up, race your buddies, occasionally go to the track, Or all of the above, one way venting is your friend. I run a pretty complicated one way check valve system with two catch cans on my street bike, and it’s overkill for most, but my motor stays together under hard core abuse, doesn’t sump, leak, smoke, blow dipsticks, or any other BS.
Several ways to accomplish relieving pressure, but yes, the stock 60 HP HD system is terrible at relieving this higher pressure, and if you have followed the MOCO’s Lame efforts over many years to reduce this pressure, and attempt to move oil and air pressure efficiently (umbrella valves for example), and their trying to eliminate sumping, you already know this.
Again, if your idea of riding is a trip to Starbucks, or running on the slab at 2,200, leave as is.....
if you have a built motor, higher comp, more cubes, love to spin it up, race your buddies, occasionally go to the track, Or all of the above, one way venting is your friend. I run a pretty complicated one way check valve system with two catch cans on my street bike, and it’s overkill for most, but my motor stays together under hard core abuse, doesn’t sump, leak, smoke, blow dipsticks, or any other BS.
Several ways to accomplish relieving pressure, but yes, the stock 60 HP HD system is terrible at relieving this higher pressure, and if you have followed the MOCO’s Lame efforts over many years to reduce this pressure, and attempt to move oil and air pressure efficiently (umbrella valves for example), and their trying to eliminate sumping, you already know this.
Again, if your idea of riding is a trip to Starbucks, or running on the slab at 2,200, leave as is.....