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Discussion Starter · #1 ·
I tried searching to see if anyone has tried this, but did not turn up with anything.

I have installed block-off plates on the valve cover breathers on other bikes that I have owned with positive results. It seems like the V-Rod breather tubes are often cracking, leaking (based on the number of open threads about it), and replacements can be difficult to find...

Has anyone tried to block off the valve cover breather ports, or is this not possible/favorable with this motor? If so, could you post your results?
 

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I tried searching to see if anyone has tried this, but did not turn up with anything.

I have installed block-off plates on the valve cover breathers on other bikes that I have owned with positive results. It seems like the V-Rod breather tubes are often cracking, leaking (based on the number of open threads about it), and replacements can be difficult to find...

Has anyone tried to block off the valve cover breather ports, or is this not possible/favorable with this motor? If so, could you post your results?
They are available from Harley-Davidson just takes awhile to get them.
 

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You can't block off the breather ports, at least both. As far as you can take it is add one way breather valves. Now that would be a vast improvement in crankcase breathing control . Object is to allow blowby pressures to escape but also neutral or slight negative pressure in the case. This helps with reduced downward resistance of the pistons moving down and reduces oil carry over where it exits out of engine. Between reduced piston down resistance and better ring seal at high rpm, there is some free HP to be gained. As the current Revolution stands, it huffs and puffs both ways and not a great system. It's tamed slightly via the small exit hole in the canister. Hell, just about every single cyl lawnmower uses a one way breather to keep oil from barfing out. Most single and v twins incorporate some form of one way valving in the crankcase breather. Long ago there was something called Doherty valves for the v rod. He's long gone now but a search will likely bring something up on the subject.
Most will just plumb up something and run a catch can. As far as hoses, they can still be had from the dealer unless they are stuck in a port in California, like the rest of my back ordered parts. Obtaining HD parts since covid has been a real shit show for all models.
Ron
 

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Discussion Starter · #5 ·
You can't block off the breather ports, at least both. As far as you can take it is add one way breather valves. Now that would be a vast improvement in crankcase breathing control . Object is to allow blowby pressures to escape but also neutral or slight negative pressure in the case. This helps with reduced downward resistance of the pistons moving down and reduces oil carry over where it exits out of engine. Between reduced piston down resistance and better ring seal at high rpm, there is some free HP to be gained. As the current Revolution stands, it huffs and puffs both ways and not a great system. It's tamed slightly via the small exit hole in the canister. Hell, just about every single cyl lawnmower uses a one way breather to keep oil from barfing out. Most single and v twins incorporate some form of one way valving in the crankcase breather. Long ago there was something called Doherty valves for the v rod. He's long gone now but a search will likely bring something up on the subject.
Most will just plumb up something and run a catch can. As far as hoses, they can still be had from the dealer unless they are stuck in a port in California, like the rest of my back ordered parts. Obtaining HD parts since covid has been a real shit show for all models.
Ron

Ah, ok. That's what I was afraid of. Really good info. Thanks for the response.
 

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Tried to search but did not found. Is there still pics from the Doherty vents available? Or even better does someone still use them and are they working as advertised?

Years ago I've tested one different brand vent but end up only huge smoke.
 

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Tried to search but did not found. Is there still pics from the Doherty vents available? Or even better does someone still use them and are they working as advertised?

Years ago I've tested one different brand vent but end up only huge smoke.
Here's an old thread on the subject. I do have pics somewhere of the damn things. If I find it, I'll post it. I do believe Trask, bought them out.
Ron
 

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Yep. That topic I found also but no pics anymore to try understanding the Doherty's setup.
Well, this took forever to find. Keep in mind, PCV valves will not work. They have calibrated leaks in them based on what engine they are used on. These Doherty valve are positive seal in one direction. I'm sure the net could scrounge up similar units.
Ron
 

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...unless they are stuck in a port in California...
I`m not alone? Had to wait 4 weeks on a AntiGravity battery (out of stock) to arrive and be shipped from LA, where are they made? Proudly made in China?? Oh, well...

From the Net:
Liquid Fluid Drinkware Automotive lighting Auto part

Mukle: do some investigation & start up the lathe... I`m in for a unit.
 
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I`m not alone? Had to wait 4 weeks on a AntiGravity battery (out of stock) to arrive and be shipped from LA, where are they made? Proudly made in China?? Oh, well...

From the Net:
View attachment 612291
Mukle: do some investigation & start up the lathe... I`m in for a unit.
There ya go. Couple of those and a good catch can, race/street ready. 2 years ago I designed a on way valve to fit inside the existing canister. The company (v rod involved) has yet to build and test it on the dyno.
Ron
 

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Mukle: do some investigation & start up the lathe... I`m in for a unit.
Unless you are going to make Ron's design come to life, you will need 2 of the Doherty designs. I spent the better part of yesterday researching and searching for the Doherty or similar valves (guess I retired too early) .. ........ I'd gladly purchase a set, to see if the benefits are as advertised......
I couldn't find the one you found on the net, unless you just found the picture? Guess dogpile.com is just giving me sh1t I don't want to see..........
 

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Here's the design concept that applies to singles and twins with rods on a common crank pin. In 4 cyls and up, the up going pistons , pressure is countered with the down going pistons. PCV valves unlike one way valves are used to draw normal blowby gasses into the intake.
The second vid explains why blocking them of isn't a good idea as was asked in a previous post.
Ron
 

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Discussion Starter · #18 ·
Here's the design concept that applies to singles and twins with rods on a common crank pin. In 4 cyls and up, the up going pistons , pressure is countered with the down going pistons. PCV valves unlike one way valves are used to draw normal blowby gasses into the intake.
The second vid explains why blocking them of isn't a good idea as was asked in a previous post.

Ron
That was my concern......... reminds me of when people said to remove your thermostat if your engine was prone to overheating :eek:
Yeah, the block-off plates I have installed on my other bikes (Kawasaki inline 4cyl) were to eliminate the stock PCV. On these carbureted motors, blocking off the stock PCV made a significant difference in how cleanly the bike would run at idle and at 1% to 15% throttle positions. It also helped to clean up the area just above the valve cover beneath the airbox.

As you guys pointed out, the crankcase breather on our V-Rods has a completely different function. Makes sense why eliminating it could cause issues.
 

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Yeah, the block-off plates I have installed on my other bikes (Kawasaki inline 4cyl) were to eliminate the stock PCV. On these carbureted motors, blocking off the stock PCV made a significant difference in how cleanly the bike would run at idle and at 1% to 15% throttle positions. It also helped to clean up the area just above the valve cover beneath the airbox.

As you guys pointed out, the crankcase breather on our V-Rods has a completely different function. Makes sense why eliminating it could cause issues.
I can see where the better vacuum with the PCV removed would help. Inline fours have smooth outflow from the case as up and down pistons cancel out the violent huffing and puffing for either a single or v twin where both go up and down together.
Ron
 
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