Has anyone ever heard of this

[Guest]

I have recently got my bike back from a reputable shop near where i live. I had to have them tune the carbs for my 4 into 1 and pods as I didn't have the time due to holiday work loads. Anyway I got to thinking about what to do with the breather line that comes off the valve cover. I have done some research and found that a lot of old school guys with older bikes such as a gs or kz or old yamaha have just used a short piece of hose and a break booster check valve to give a proper amount of vacuum to the crank case. Something like this

This is the first I have ever heard of it so please let me know. I do have one from another project and if it seems viable then hey what do I have to loose.

[nejeff]

I know for sure you don't want to cap it off, not familiar with the valve you are talking about.

You can put a little breather filter on it or just run a long hose down to the bottom of the bike and forget about it

[Deuce]

Looks like a pcv valve. Positive Crankcase Ventilation. Many people will write "pvc" valve, which it ain't.

[GregT]

Don't do it - those valves work with vacuum fluctuations. On an inline four there is not enough fluctuation to make it work.
With the valve not working, you risk pressurising the cases.
Just run an extended hose to a catch can beside the battery.

[Steve]

I can't see exactly where it's mounted, but it appears to be connecting the top of the valve cover with the top of the crankcase.

Essentially, those are two ends of the same space, so you are not "ventilating" ANYTHING.

If you aren't particularly worried about your contribution to pollution, just put about three feet of hose on the breather port on the valve cover, run it along the frame, down the back of the engine and let it hang below the swingarm. If you put a little bit of an angle cut on it, it will help generate a bit of vacuum to help any blow-by down the hose. I have done that on my son's 650 (with pods) and it seems to work well.

Before the arrival of the PCV valve on automobiles, that is the way all the cars were ventilating their crankcases.

.

[JTGS850GL]

I can't see exactly where it's mounted, but it appears to be connecting the top of the valve cover with the top of the crankcase.

Steve, I think the other end is just loose in the air. If I understand which valve he's using, it's essentially a one way check valve similar to a PCV valve but with a higher pressure opening point so there is a potential for higher crankcase pressures but not by much. Personally I'd just vent it to either a catch can or just dump it overboard. Much simpler and less prone to failure.

[Steve]

I remember someone posting something several years ago about pumping down the crankcase to let the pistons run in more of a vacuum. On something like a BMW boxer twin, it might make sense, but the overall volume in an inline four engine remains rather constant, so there won't be any fluctuations.

.

[tkent02]

Mine is just a hose, nothing comes out, so it's just aimed under the swing arm.

[mmattockx]

This is the first I have ever heard of it so please let me know. I do have one from another project and if it seems viable then hey what do I have to loose.

Ducati use a reed valve on some of their crankcases for the same purpose.

I remember someone posting something several years ago about pumping down the crankcase to let the pistons run in more of a vacuum. On something like a BMW boxer twin, it might make sense, but the overall volume in an inline four engine remains rather constant, so there won't be any fluctuations.

.

Steve, the pro stock drag bikes used to run on board vacuum pumps to draw down the crankcase pressure. It has been a while since I paid attention to them, so the rules may have eliminated that practice. They wanted as much vacuum as they could get and this resulted in something like 5-8% horsepower increase, so there are certainly significant fluctuations and measurable advantages to running your crankcase under vacuum.


Mark

[dantodd]

Steve, I think the other end is just loose in the air. If I understand which valve he's using, it's essentially a one way check valve similar to a PCV valve but with a higher pressure opening point so there is a potential for higher crankcase pressures but not by much. Personally I'd just vent it to either a catch can or just dump it overboard. Much simpler and less prone to failure.

It looks to me like the valve feeds in to the pod. Seems odd as any oil end up in the carb, I'd worry a little about it getting dirty.

[dorkburger]

I connected a hose to the valve cover and ran it to the pictured piece if copper tubing stuck into the exiting exhaust flow. It draws a small vacuum on the crankcase thru the venturi effect.

Probably has a minute effect, if any, and is likely the result of my reading one too many articles about drag race cars.

[adam]

I was just wondering because the bike seemed to run smoother when the stock air box is connected. I know some people would just say put the air box back on but I am stubborn and don't want to. I talked to a older buddy and he said its because the minute amount of vacuum the stock air box causes aids in the actuation of the piston rings which is why it seemed to run a little smoother. He suggested trying to figure out a way to duplicate that effect but had no real solutions, he said everyone finds a different way of dealing with it through trial and error. I guess I will try a long piece of hose with a clear universal fuel filter on the end will be the starting point. Maybe the small opening on each end will create a small enouph vacuum effect to make it work. I guess we will see.

[JJ]

I was just wondering because the bike seemed to run smoother when the stock air box is connected. I know some people would just say put the air box back on but I am stubborn and don't want to.

They generally do run a lot smoother with the stock air box and a stock (or K&N factory replacement) air filter. Some people have great luck with pods, but there's a good deal of effort involved getting them tuned right. Go ahead and be stubborn. Just don't damage the engine by running it too lean. Read the spark plugs, they'll tell you what to do.

By the way, a "reputable shop" would have put a breather filter, catch-can, and/or routed the breather tube correctly.

[hillsy]

The reason your bike runs better with an airbox is that it provides a measured amount of still air for all the carbs to draw from.

Plus the airbox to carb inlet rubbers act as velocity stacks to aid atomisation of the fuel.

It's got nothing (or very little) to do with crankcase vacuum.

[Grimly]

I can't see exactly where it's mounted, but it appears to be connecting the top of the valve cover with the top of the crankcase.

Essentially, those are two ends of the same space, so you are not "ventilating" ANYTHING.

If you aren't particularly worried about your contribution to pollution, just put about three feet of hose on the breather port on the valve cover, run it along the frame, down the back of the engine and let it hang below the swingarm. If you put a little bit of an angle cut on it, it will help generate a bit of vacuum to help any blow-by down the hose. I have done that on my son's 650 (with pods) and it seems to work well.

Before the arrival of the PCV valve on automobiles, that is the way all the cars were ventilating their crankcases.

.

For a couple of years I had the crankcase fumes venting along a hose that ran down the swingarm and off the end. When the rings were getting a bit worn, the water vapoour coming out at idle in town was noticeable, prompting a couple of queries about steam power.