Crankcase breather tube setups??

[john jupiter]

Does anyone have anything interesting custom setups out there? Ive seen a few overflow cans attached to them but wondering if there is a way to get it hidden and out of site.

[JimF]

I believe the stock (street bike) implementation is just run a long tube and vent it beyond the rear tire. An interesting side note is the my tube has a Pirelli logo on it, so I assume it was made by the same company that makes tires today. If you still have your original tube you might wipe off the muck on it and maybe find a logo.

My understanding is that only if you are going to race a bike do you need to have a catch basin for the crankcase breather. I assume that's so race bikes aren't misting any slippery shit onto the track.

I have seen most everything including a beer can used as a catch bottle, so I guess that perhaps there are little rules governing what they can be made from save for glass or something too easily breakable. I once bought a nice aluminum overflow can from the UK that had a threaded spigot on the bottom for draining the contents. I may still have that one somewhere.

I kind of recall seeing one built into a racing rear fender, the short fiberglass racing fender that mounts just ahead of the tire.

[MotoMike]

hey JJ

I think you are supposed to use some sort of uber-cool catchment can, mount it out there for god and country to see. It will suggest there might be a fire breathing highly modified beast lurking between the frame rails. Something like a discarded rat poison can or something like that.

[john jupiter]

haha i was thinking more along the lines of shortened/altered and much less conspicuous...

[sebouh]

Hello,
I have the same questions.

I know what the stock tube looks like. Any pictures of modication or alternative breathers? The more minimalist the better.

Thanks
Sebouh

[Jon Pegler]

Maybe like the early mototrans breather?

IMGP0479.JPG

[JimF]

I think I got this purpose-built aluminum catch tank from TGA years ago but I don't see it on their website now:

IMG_0619_1.JPG

However they do have the short racing fender with the built-in catch tank:

http://www.tga.co.uk/

ducati_slpash_tank.jpg

[MotoMike]

I get my models mixed up but I know that some had the breather tube go to a little flapper valve in the breather box which I think served to keep a slight negative pressure in the crankcase. The previous owner had installed a clear hose as Jim described. I found no oil build up at the exit end of the hose, but near the engine it was almost black. Based on that observation, I don't think much mist is exiting the breather tube. Since my stock breather setup is long gone, I followed the long used method of routing it out the back along the frame rail. After discussions with Bob and other's here and in part to address an issue I had with oil drooling from the sprocket shaft, I installed a PCV valve in the end of the hose. I've not since had the oil leaking from the sproket, but don't know how long it was building up there before it made itself known.

Mike

[JimF]

My plastic tube is the same, to some degree I think any oil mist that escapes from the pressurized crankcase is supposed to 'condense' on the tube's walls and then in theory trickle back into the case from whence it came, but I could be wrong about the notion that anybody gives a rat's ass if that little amount of oil returns. My engine leaks more oil in a week that the breather has likely exhaled in a lifetime.

I have a bevel twin that has the flapper you mentioned. I guess I never thought about it inflicting a little back-pressure. I thought it was intended to be sucked closed from negative pressure inside the crankcase and prevent dirt from being drawn in the 'back door' so to speak.

I think only racers uses catch basins as I believe it's required the same as safety-wired fasteners and oil pans under the engine are - so if your engine grenades you don't lay a James Bond-ish oil slick down and crash the next six riders behind you.

[wcorey]

I welded a couple of spigots to the lower frame seat/shock support tube on the R/T, one down near the breather outlet and one up under the seat, such that the frame tube itself also becomes (the majority) of the breather tube. Looks to me like a similar thing could be done with the road frames. I was saying that I'll likely stick a pcv valve on the end under the seat but Bob has pointed out that it would be more effective nearer the crankcase, so that's easy enough also. I can't find an automotive one with similar diameter/volume capacity as the breather tube so I'll likely make some thing up.

Bill