Crankcase breather

Today, it's an emissions or pollution thing. Years ago, all engines vented to atmosphere, even cars.
 
Like the factory did it? Well yeah!
That's my goto, a big part of why I stick with stock air boxes in front of stock carbs.
Standards 76-79
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Specials 80 up
80 up specials PCV.jpg
One I made for madness. a 79 750; used a later breather box and plumbing then made some copper risers and flanges to penetrate and seal against the uni filters.
Madness PCV.jpg
The set up always goes down then back up to the airbox. I think the theory is at lower speeds any oil escaping the crankcase sits in the plumbing, then at higher RPM increased air flow pulls it through the carbs to be burned in the combustion chambers.
Not all cleaned up for viewing! :laugh2: :redface: several thousand miles since installed.Much of that running hard.

Skull told you what would happen if you let gary's messy bench near a nice bike...
 
I found mine at O'Reillys Auto parts. Tho they couldn't find it in their system.. I spotted it on their hooks lol
Its just a Ford etc.. style old brake booster check valve
 
Power brake check valve into some short black tube, clear vinyl running down the back of the engine, under the carbs. Curves up to the frame spine, topped with a cheap push-in breather filter between the foam pods. It keeps everything in the area well oiled, although it seems like less of a mess since I replaced the O'Rilley's 20w50 with Castrol GTX.
 
Heres my solution to the problem and even has a vacume gage to let u see wat ur makeing . Comes with all mounting hard wear and even the hose to attach it with and clamps for 25 usd. Shiped right to ur front door has a filter built in and everything a man could want for the price it blew my skirt up anyway
 

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Dual outlet breather box converted to a single. thin walled crankcase vent hose from MikesXS with two light external springs and a billet filter mounted to the crankcase. Easy to remove the foam from the filter and wash at service times. Hasn't left a spot of oil on the ground in over 3000klm.
Where might I ask you purchased those filters? Great set up!
 
Its called a oil tank and at wish .com if u look around a bit u can snag the 1 like i got with internal filter,hose & clamps and even a vaccum gage just for good measure in a veriety of colors for lik 20 bucks
 
That's hard to say. I would think the hole in the rubber plug should be a little bigger because you're down to one pipe now, but maybe not as big as it would be by removing the plug. Maybe someone with a later factory single pipe breather could check the hole size on that for you?

Normally, your breather breaths in and out as the pistons move up and down. The check valve is a one way valve that lets pressure out but not back in. That creates a small vacuum in the crankcase and that's supposed to be beneficial for a couple reasons. First, the engine is supposed to make a bit more power like that. Second, that slight negative pressure can help prevent oil leaks and possibly alleviate minor ones you may already have.

Many of us who run pods use a short length of hose and locate the check valve above the pod filter. If any oil or oil mist does come out, it will just get recycled through the engine. This sort of mimics the factory set-up of having the breather hoses fed into the airbox. I had no clearance issues setting this up and in fact, it uses less hose and takes up less space than the factory set-up. This was my original set-up when I still had K&N pods .....

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I have since switched to UNI foam pods because the K&Ns don't work well with our CV carbs. The check valve set-up remains the same. I notice you have the K&N pleated type pods. They will cause you carb tuning difficulties.
Interested in your comment that pod filters will cause carb tuning issues. Can you please elaborate? Thanks.
 
Pleated K&N type pod filters are the troublesome ones. The pleats disrupt the air flow, make it turbulent, and that messes with the slide lift on these CV carbs. Best pods to use on these are the straight foam UNI pods.
 
Pleated K&N type pod filters are the troublesome ones. The pleats disrupt the air flow, make it turbulent, and that messes with the slide lift on these CV carbs. Best pods to use on these are the straight foam UNI pods.
Thx. I’m running 32mm PWK carbs. At the filter end they are 54 mm or close to 2-1/8”. Had a look at Uni’s website an it looks like the diameter jumps from 2” to 2-1/4”. Does the urethane flange have enough “give” to stretch the 2” over my 2-1/8” carbs?
 
The PWK are a regular slide carb so you could use the K&N type filter on them. But yes, if going with a UNI, the 2 1/4" will tighten down just fine to 2 1/8". The 2" version would be a stretch and very tight. I don't recommend it.
 
Gre
The PWK are a regular slide carb so you could use the K&N type filter on them. But yes, if going with a UNI, the 2 1/4" will tighten down just fine to 2 1/8". The 2" version would be a stretch and very tight. I don't recommend it.
great thx
 
Dears,
Currently I am sandblasting the two airfilter housings. I noticed both breather connections are cut of and the remaining parts into the housings are closed.
As my bike will be the subject of an official check, to get a licence plate again, I intend to make some kind of engine breating system, returning the fumes into the engine.
After reading all articles on this subject on this forum, I got some ideas to reinstall an improved engine breathing system. Still some doubts however.

Basically the volume of both cilinders comes out of the breather each rotation. Still only one cilinder sucks in air during that rotation. This means the vapor will be pressed into the other air filters, flowing to the other air filter from which the engine sucks fresh air that moment. I expect this will pollute the filters with oil. Can hou agree?
I do not understand the use of pcv valves on this twin; to my opinion the vacuum during the upgoing stroke, will influence the piston velocity and thus the power, though very slightly naturally.
Recently I worked on a Honda VT600 of a relative (you would not want to own one); this V-engine has a breather hose coming from each cilinder, leading to a small reservoir. This reservoir has a tube connected to the air filter box, and has a plugged drain hose which need to be drained every now and then.I think this is a nice solution as the reservoir collects oil (when there is any) and acts as a buffer volume for the fumes. Please give me your thoughts.

Bert
 
Dears,
Currently I am sandblasting the two airfilter housings. I noticed both breather connections are cut of and the remaining parts into the housings are closed.
As my bike will be the subject of an official check, to get a licence plate again, I intend to make some kind of engine breating system, returning the fumes into the engine.
After reading all articles on this subject on this forum, I got some ideas to reinstall an improved engine breathing system. Still some doubts however.

Basically the volume of both cilinders comes out of the breather each rotation. Still only one cilinder sucks in air during that rotation. This means the vapor will be pressed into the other air filters, flowing to the other air filter from which the engine sucks fresh air that moment. I expect this will pollute the filters with oil. Can hou agree?
I do not understand the use of pcv valves on this twin; to my opinion the vacuum during the upgoing stroke, will influence the piston velocity and thus the power, though very slightly naturally.
Recently I worked on a Honda VT600 of a relative (you would not want to own one); this V-engine has a breather hose coming from each cilinder, leading to a small reservoir. This reservoir has a tube connected to the air filter box, and has a plugged drain hose which need to be drained every now and then.I think this is a nice solution as the reservoir collects oil (when there is any) and acts as a buffer volume for the fumes. Please give me your thoughts.

Bert

Hi Bert and welcome,
I think you are confusing what happens to the air the engine takes in through the carburettors with what happens to the air in it's crankcase.
With it's crankcase breathing system blocked off as you have described your engine will over-pressurize it's crankcase and leak oil everywhere.
The later single and earlier twin breather nozzles are there to direct the oil-laden crankcase breather air through hoses into the stock air filters
thus making the oiling system a closed loop to keep the EPA Nazis happy.
I'd suggest you put your bike back to stock before getting it inspected


.
 
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