For those with pods - what to do with breather hose?

[Chuck78]

resurrecting an old thread here, as I feel it is still very pertinent.

normally my engine would behave pretty well if I can ride normally, but a vintage 4cyl bike just tempts me far too much to twist that throttle open quite a lot...

I noticed when I am on spirited rides out in the hills (i.e. riding aggressively our in the best Appalachian twisties I can hit in a day trip from home in SE Ohio & sometimes into West Virginia), I always come home with oil mist all over the undersides of the bike. this does a great job in preserving everything, making sure it will not rust/corrode, but makes for quite a messy bike. Rear tire traction is also a concern.

I started noticing that race bikes quite often had some sort of makeshift catch can. This is when I really started paying attention to this mod.the guy actually gave me a PVC catch can that was fabricated for his race bike when he parted it out. getting my bike ready for the riding season, I clean a whole lot of oil grime from the undersides of it, and so I referred back to this thread.


I currently just have a K&N breather filter on the end of the hose, and had it sitting on top of my air filter, so drips would just hit my K&N dual oval pods. I've still got a lot of misting out all over.


one of my first thoughts was just to get a bunch of fittings and connect all of the carburetor sync ports together with a brazed copper tube manifold that I would fabricate, so that I would have a constant vacuum on the crankcase. any moisture Vapors would get sent out the exhaust, and I don't think it's a problem to introduce minor amounts into the cylinder, as humid air gets sucked in there all the time. this might lead to a little exhaust smoking under aggressive riding, and could also maybe dirty the spark plugs up a little bit unless you are already running on the lean (hot) side.

with the factory set up, I noticed there is a drain hose on the bottom of my 77 GS 750 air box, and the oil would potentially just migrate down into the bottom if there was any condensation forming into liquid again. Vapor mist would of course get sucked into the carbs.

you probably wouldn't want to vent all of the vapors into one pod, as you would have uneven running conditions. it would be even worse if you vented it into only one synch port, as you would then have unmetered air going into that cylinder


the $45 Krank etc copy one way check valve is an interesting concept, and I am going to look at that KLR forum link in a minute. it seems like it from might quite possibly allow the engine crankcase to operate in a vacuum (reducing potential oil leaks and pressure against the pistons & possibly reducing blowby), as it will expel excess pressure, and then when the pressure drops, close itself, sealing the crankcase off into a slight vacuum condition. this would not help the oil migration out of the breather filter, but this seems to be a big positive if you are not running the hose into the air box or pods or synch ports

[Chuck78]

These $45 billet aluminum catch cans on eBay from China would be a good basis to make something really trick looking, but I only see one hose thread connection. More work would be required. Also the orientation of the tank looks to need mounted horizontally.

I think I would possibly modify this to mount it vertically and maybe even put a sight glass in it like the fancy car tanks that are larger.

I also thought I could probably pretty easily fabricate something out of one inch or 1.25 inch copper pipe and fittings. That would look pretty trick, definitely home-brewed looking, but much better than PVC

[Chuck78]

For $50, if you run pods and don't tap your vent back into the carbs or synch ports, these seem like an excellent idea. The name brand units are about $90-something. This is an "Asian" piece... In theory it should allow to vent off excess pressure without ever sucking more air back in, so it will run a reduced crankcase pressure and cause less blowby, and less oil seepage.



HARLEY, S&S, ULTIMA OR CUSTOM V-TWIN SIFTON CRANK CASE VENT VALVE (PCV)

No need to pay for the higher priced vent valves (Krank, Spyke, ET, Hayden) - get the same functionality from this generic version at a better price

No power gain claims here - just a great way to reduce the pressure inside your engine cases

Only passes air in one direction - put one in your vent line to create a lower internal case pressure

Helps reduce leaks around gaskets caused by higher internal engine pressure

Lowers back pressure behind the pistons for smoother running and less blow-by

Two 3/8" hose barbs - Includes two Gates type hose clamps - Overall length 3", diameter 1-3/8"

PLUS, ONLY OURS COMES WITH AN EXTRA REPLACEMENT UMBRELLA SEAL!

http://www.ebay.com/itm/CASE-BREATHER-VENT-PCV-VALVE-HARLEY-EVO-SHOVELHEAD-PANHEAD-TWIN-CAM-KRANK-/331797342195

http://www.ebay.com/itm/SIFTON-CASE-BREATHER-VENT-PCV-VALVE-HARLEY-EVO-SHOVELHEAD-PANHEAD-TWINCAM-KRANK-/331788075461

Unlike the automotive type, these can be disassembled for cleaning, great for wet sumpers

Put the "seam" on the engine side

Easy Installation - Nice Chrome finish

Sold Each - Asian Import

See the last picture for the breather check valve used in conjunction with the EBOC oil collector/reservoir - sold separately

[John Park]

Maybe I'm missing something, but as I understand it in a GS motor - four or twin - there are as many pistons going up as down, so if the piston seal were perfect there would be no need of a breather. How can you generate a suction without something to suck? A one way valve in there is going to have hard time finding any flow going anywhere but out.

Motors like singles and opposed twins have big venting problems and +/- pulses but inline fours and 180 degree twins don't. So how would air get sucked back in if there's no suck? I can see how the pressure would fluctuate but what would make it go negative?

[ben2go]

The rotating mass and heat builds pressure in the crankcase which must be vented.When using a positive crankcase ventilation system (PCV) with a catch can,the catch can, can be put under a vacuum using a T fitting between the carb filters, or intake boots, to create a slight vacuum in the crankcase through the hose connected to the engine's vent fitting.Race engines have been using this set up for a very long time.My racing karts used the same set up.Very simple system to help the engine run a little better and cleaner.

[John Park]

The rotating mass and heat builds pressure in the crankcase which must be vented.When using a positive crankcase ventilation system (PCV) with a catch can,the catch can, can be put under a vacuum using a T fitting between the carb filters, or intake boots, to create a slight vacuum in the crankcase through the hose connected to the engine's vent fitting.Race engines have been using this set up for a very long time.My racing karts used the same set up.Very simple system to help the engine run a little better and cleaner.

Rotating components won't produce pressure, only turbulence. Granted, the crankcase air will expand once as it heats up. But there won't be any suction in there unless you tap into the intake vacuum, which is what the PCV does. PCVs are nice, and they don't upset the mixture significantly because the blowby gasses are just CO2. The slight vacuum you mention is there in theory, but it only exists if the PCV can keep ahead of the blowby rate. When the system reverses, the gasses have to go somewhere else and many automotive designs end up soaking the paper air filter or spewing sooty crap on the throttle body.

I just wanted to point out that the GS motors don't wheeze in and out like Harleys and British twins do. Nothing is going to get sucked into the breather unless you create suction.

[dorkburger]

I saw a setup similar to this on a turbo GS many years ago, and eventually did it to mine when I added pods. The exhaust pulls a small vacuum on the pipe (venturi effect). The pipe is connected to a hi temp silicone hose and connected to the valve cover fitting. I tested it, and verified it does pull vacuum.

[Chuck78]

good points. I was actually thinking about that before I got back to reading this post, about the one way check valve. Definitely sounds very important on a lot of twins and ALL single cylinder bikes. Maybe pointless to add 1 to a GS four, as it did occur to me a few hours after posting that rehash, that the pistons are always going the opposite of each other, two up two down. blow-by and thermal expansion is what really increases as you run them extremely hard, and this is where the catch can comes in play. I might try to employ a catch can and find some brass hose barb fittings that have the thread of the synch ports.

[OldVet66]

I have one of the check valve systems on my bike. I ran the hose to the check valve near the transmission and continued on under the frame where the other vent hoses hang. The crank vent does work to hold a vacuum in the crank case, but an inline 4 tears up the valve. I think they work much better on a Harley. I may get around to trying one of the automotive valves before I give up on it. When they work, you can notice a nice little increase in low end power, they just don't work for long before the valve material wears out.

[Chuck78]

These are pretty nice looking and ready to go, but a bit pricey (mentioned earlier in thread)

http://www.discovolantemoto.co.uk/crankcase-breather-tank-round-447-p.asp

[Buffalo Bill]

So chuck, the above can will collect oil to be drained after a ride?

[ben2go]

So chuck, the above can will collect oil to be drained after a ride?

I drain the one on my GST, when I change the oil every 3-4000 miles.It has about a table spoon, or just a bit more, of oil in it. I have very little blow by.

[Sam 78 GS750]

Resurrecting this thread, as I'm a bit confused. There's a lot of talk about the breather vent, and a "crankcase vent" as if they're two different things. Is there some kind of vent from the crankcase that I don't know about, or when people say crankcase vent are they actually talking about the tube that comes off the breather cover and normally gets routed to the airbox?

[ben2go]

Resurrecting this thread, as I'm a bit confused. There's a lot of talk about the breather vent, and a "crankcase vent" as if they're two different things. Is there some kind of vent from the crankcase that I don't know about, or when people say crankcase vent are they actually talking about the tube that comes off the breather cover and normally gets routed to the airbox?

Yes. The terms are interchangeable. Some vent from the valve cover and some vent through a spot down on the case. I think all Suzuki's vent from the valve cover. Anyway it goes, it lets air pressure escape the crankcase and should be filtered to prevent dust and debris being sucked in on startup.

[Sam 78 GS750]

Thanks for the explanation and the quick response, ben2go.

Would there be any benefit to a PCV valve, or would a simple catch can suffice when going from airbox to pods? If you do use a one way valve, do you have to hook it into the intake somehow or are folks just doing that so they don't get an oil mist on the bike?