I wouldn't leave it open,... it'll just puke oil mist all over...

Tidiest solution would be to route it to the air filter,...

Easiest is to stick mini filter on it...  
I'd try to route the hose somewhat upward, in the hopes that the oil mist would condense at the top, and flow back down into the head...

The real problem with a thumper is the large volume of air that is moved in & out of the crankcase as the piston moves. On multi- cylinder engines this is confined to the crankcase mostly as one piston goes up there is another coming down & the volume of air in the crankcase remains roughly the same.  With the engine running put your thumb lightly over the end of that breather hose & feel the pulses of air at idle. I wouldn't want to route that to a pod filter on the carb becauase of the interference it might cause with air flow. If you had some sort of air box around the filter I would put it there.
Personally, I would loop the hose up under the tank as high as possible to give the oil vapor a chance to drain back into the engine & then down the front frame tube. Then I would put the largest pod style filter I could find on it. Zip tie everything & trim the excess off the ties to make it as neat as possible. The better that vent can breath, the fewer oil leaks you will have.

On my 2.3L ford mini-stock engine, The normal pvc hose is routed to the side of the engine with a pcv valve mounted inline, then the hose continues to an air pump check valve on the end of a short piece of pipe welded at an angle into the header collector.
The exhaust passing the end of that pipe creates a suction that keeps pressure from building up in the engine. I have a pod type filter  mounted on the valve cover to allow air to be drawn in to prevent the gaskets from being sucked in. This system cured 90% of the oil leaks on my engine. BTW, this engine turns over 8000 rpm in competition . When I first bought this car it blew oil out everywhere.
If you run the engine long enough, any moisture in the oil will be gone from the heat. Consistent short rides don't give enough time to rid the oil of contaminants & would be a reason for more frequent oil changes.

Put a PCV valve in the line, and run it to the vacuum tap on the carb?...
Pulse injection?...

Never mind... ...

For what it's worth, on my Ryca kit I have a hose running from the vent tube on the cylinder head along the bottom of the gas tank, then down to enter the front of the battery box, and then up to the rear plate of the battery box. On that plate I've drilled a hole to mount a K&N crankcase breather filter inside the battery box.

I don't know if the routing is ideal.

The bike (with almost 20K miles) is using a fair amount of oil (5W40), but there's no visible smoke from the pipe (there are dry carbon deposits inside the muffler), only very minor gasket seeps, and no noticeable dribbling from the crankcase breather filter.

I suspect valve guides and/or piston rings are the problem, not the crankcase breathing.

for what its worth, I chose option number 3 and it works fine. Picked up a little K&N type filter from advance auto parts and route it to the back down low.

Here's what mine looks like...I've since changed to a cone air filter mounted right on the carb, but the crankcase breather is still the same.

Applied Racing makes a nice tiny filter that goes on the end of the hose, very unobtrusive and effective unlike the K and N model.
Lead the hose back and down along the rear frame by the swing arm and you are all set.
Gyrobob wrote on 10/02/11 at 10:47:24: