Transmission Ventilation?

[jordanscycles]

There's a tube coming out of the top of my transmission that connects to the airbox, but what I'm curious about is what this is for. I just read that if you cool the transmission it works better? so maybe it circulates cool air into there? anyone have an insight on this?

[Airhead]

Its just a breather to stop the transmission casing from building up pressure as the engine becomes hot.

...Paul

[barkwindjammer]

Someone posted a thread recently with a pic showing black rubber tubing which had a small bulbous plastic section in it, I would guess a one way valve, and would also imagine this would allow pressure to flow out of the engine casing, transmission or rocker cover-but not allow crap to be sucked back in the direction of said 'expensive shit'

a clever 'mod', just wondering if these valves would be available on the open market?

[Cynic]

Someone posted a thread recently with a pic showing black rubber tubing which had a small bulbous plastic section in it, I would guess a one way valve, and would also imagine this would allow pressure to flow out of the engine casing, transmission or rocker cover-but not allow crap to be sucked back in the direction of said 'expensive shit'

a clever 'mod', just wondering if these valves would be available on the open market?

Its just the greenies making the bikes heavier, as the pistons move they cause pressure underneath them. There will also be a little blow by on the rings this needs to be vented or bye bye seals. Once upon a time it was a pipe out of the cases ( you must have seen a Triumph bonny with an oily piece of hosepipe by the no plate) but then the started routing them to the airbox as the engine burns the vapour so cleaning things up.