Blow-By Attachments To Pods

[tracer1966]

I replaced my stock air filters with pods, and recently figured out a way to run my blow-by hoses into the back of my new pods.

The fixtures are from ACE, and cost about 5 clams each. Each fixture needs two large nuts (insert Michael Scott comment here). One stops the fixture from butting up against the outside of the pod (as seen in the pictures), while the other clamps the fixture to the pod from the inside.

I've been running them for about 2 months now, and they seem to work well.

 

[barelycompetent]

Interesting mod, just curious but what is the benefit of doing this? By blow by hoses Im guessing you are talking about the breather tubes? If that is the case why not just slap a small pod filter on the tubes and leave them hanging in between the pods? Im not knocking the setup by any means just curious is all lol.

 

[racerdave]

I've thought about that before. I also have wondered what effect the slight vacum you might get, would do pulling in a small amount of oil into the intake tract.

 

[XSLeo]

They did this as stock for the BS34 carbs. The breather hose ran down, split and went into each air box just in front of the carbs. I have thought of doing something like this.
Leo

 

[Mharrington]

By plumbing back into the air intake it retains the Positive Crankcase Ventilation process- PCV. The automotive world debates this same procedure as well. Its beneficial to have the crankcase not only vented but to have a constant vacuum pullingthis air from the engine- thus plumbed into the intake. On our OLD cars that is the PCV valve that goes into the air cleaner housing. But now you have air with oil vapor and even sometimes a little oil contaminating the fresh air coming in. Ive read on a street only vehicle there is no significant reduction in performance- the benefits of a proper circulating crankcase air out weighs the benefits of pure air coming in.

I say do whatever you like. On my muscle car I replaced the PCV valve,system with a chrome breather and all is well. On my bike I kept it stock.

 

[retiredgentleman]

Yes, positive crankcase ventilation, with the crankcase vapours being drawn into the carbs was a common method used in cars and trucks for many years.

My 78SE has the crankcase vent lines going into my air boxes. It works extremely well.

With cars and trucks, they used a small foam air filter, with a direct path of fresh air going into the crankcase. This meant the crankcase was constantly being purged.

However, my bike does not have a fresh air intake to the crankcase, so its not being constanly purged as was done in cars/trucks. My 78SE vent lines just keep a slightly negative pressure in the crankcase.

 

[racerdave]

Some PCV valves were ducted in below the throttle plates not into the venturi. some went to air cleaner, unless my memory is really bad.

 

[tracer1966]

No criticisms taken--no harm no foul. When getting around to doing the mod, I actually forgot about the number of other threads I had seen that discussed this issue.

I have also noticed that later stock air boxes had barbs for the breather hoses, and I remember the PCV valve on a '64 Dodge Polara I once had. So I figured it would be ok.

But mainly I was looking for a way to route the breather hoses that kept oil mist from spewing somewhere on the bike or ground in front of the rear tire. Toward that end, it's been doing well.

As always, thanks for the comments/explanations!

 

[barelycompetent]

I can see the oil mist not spraying on the rear tire as a definite benefit lol. So I think I have the basics of it understood, but wouldnt that oil mist have an adverse affect on the carbs and the pulling of clean air into them? I know on a properly serviced machine its probably not enough to cause a problem. Just trying to wrap my head around it.

 

[retiredgentleman]

I can see the oil mist not spraying on the rear tire as a definite benefit lol. So I think I have the basics of it understood, but wouldnt that oil mist have an adverse affect on the carbs and the pulling of clean air into them? I know on a properly serviced machine its probably not enough to cause a problem. Just trying to wrap my head around it.

If you have any real amount of oil coming out of the crankcase vents, then you have an engine with worn out internal parts. Repair the engine.

When I take my air filters out of my air boxes, for their annual cleaning, I eye ball the line from the crankcase vent. In 7 years, I have never seen any oil from those lines at all.

In reality there is no quantity of air/oil mist from the crankcase vents. There is no flow of air into the crankcase, so as a result there is no flow outward. Contrast that to the way cars and trucks used to do it....................they had a supply of air into the crankcase, so it was a continuous flow through the crankcase.

 

[tracer1966]

I can see the oil mist not spraying on the rear tire as a definite benefit lol. So I think I have the basics of it understood, but wouldnt that oil mist have an adverse affect on the carbs and the pulling of clean air into them? I know on a properly serviced machine its probably not enough to cause a problem. Just trying to wrap my head around it.

I also wondered the same thing, and figured I was going with what is hopefully the lesser of 2 evils. So far OK.

 

[DogBunny]

The problem with schemes like in the original pictures is that the engine oil contains suspended metal particles, exactly the kind of stuff that you want the air filters to remove, and you are sending these metal particles directly into your cylinders. A better plan would be to direct the blow-by to the outside of your pods, then it is at least filtered. I believe that this is how all of the various years handled blow-by from the factory -- blow-by went into the air boxes and was filtered by the stock air filters before there was any possibility of it entering the carbs.

 

[XSLeo]

The breather hoses hooked to a barb on the bottom of the air box just before the carbs. This barb was the end of a tube that opened into the air stream just in front of the carb.
As the engine runs some oil gets splashed around inside the crankcase. This oil turns into a mist. As the pistons move down they push this mist laden air down out of the cylinders into the crank case, up the can chain tunnel out the breather. There is the funny clip in the head and the baffle in the breather box that helps condense this oil mist back into oil.
This oil drains back down into the engine.
If you engine is in reasonable shape very little of this oil mist escapes through the breather.
This air that get pushed out the breather gets drawn into the intake stream. This builds a small vacuum inside the crank case. This help prevent some oil leaks and helps seal the rings better. Not sure how that work but it does.
If you don't want to route the breather hoses into the intake tract you can use a power brake check valve. A Dorman item number 80190. Found on the HELP rack at most parts stores. It is a one way valve that has two size of hose barbs. The larger one is a perfect fit into the breather hose where it comes from the breather. The small barb is 3/8 I just run a 3/8 hose off there to down below, behind and off to one side of the engine. If any oil blow by escapes the breather the hose diverts it away from the tire.
I have been thinking of running the 3/8 hose to a tee then running it to both of my Uni-filters such as shown earlier in this thread.
Leo

 

[Liftedzuki]

What about making it like the old XS and blow it into the chain?

I considered doing this, simple and kind of a cool concept, I plan on uni filters as well

 

[CDNTX650]

Not correct at all rg. My 74 is re ringed with low k to start, and hasdgood compression, and proper oil level, after a ride there is a bit of oil on my frame by the breather hose. These bikes will spit oil to some degree. Probably why yam changed the breather setup a bunch over the years. I just route my breather to the chain.

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[CDNTX650]

I also noticed, my double outlet breather had no restrictors at all. When i first rode the bike is was bad with oil out the breather. So i blocked one outlet completely. Now its much better.

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[retiredgentleman]

Not correct at all rg. My 74 is re ringed with low k to start, and hasdgood compression, and proper oil level, after a ride there is a bit of oil on my frame by the breather hose. These bikes will spit oil to some degree. Probably why yam changed the breather setup a bunch over the years. I just route my breather to the chain.

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Perhaps you forgot to re-install the oil mist baffle (labrinth seal) in the head, when you had the top-end apart. That little device prevents any large drops of oil exiting the engine.

I stand by what I said. No visible oil drops come out of my 2 breather hoses. My 78SE also has rubber orifices inside the 2 breather outlet pipes. Your 74 may not have those.

Yes, Yamaha made quite a few changes to the crankcase breather over the years. The system on my 78SE, routing into the air boxes, works extremely well.

The only oil that gets on my chain, is what I apply as chain oil.

 

[CDNTX650]

Its there. There is reports of some doing it, like mine, while others dont. Plus all the oil level revisions along with baffle revisions. I think i read pre- 74 dont even have that oil baffle in the head. Since this was yams first 4 stroke pretty safe to say they handt a clue. The terrible trans gear ratios are evident of that.

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