Just bought a 2004 and doing some maintenance. Noticed that my crankcase vent is just open to atmosphere with no hose connected. Is that normal or did the previous owner lose something? Can't imagine this is a good way to run in dusty conditions.

I think there should be a hose from there to the air box

Hmm not seeing anything obvious. Guess I'll pull the subframe so I can get a better look.

I've got the same machine, pretty sure mine just has a hose that is routed rearward and ziptied together with the carb vent tubes. Unfortunately I can't go have a look at it to verify as I just sent it with someone to the coast so I can ride next week.... (Yay)

Edited February 23, 201412 yr by ymirtrials

The gearbox doesn't really breath much (unless there is seal damage somewhere) but some expansion may result from heat and splashing around of the oil. Other than dust the reason for the hose is water intake. A hose running up then back down again or in the airfilter is a good idea in case you ever run into a deep mud hole or cross a creek. A little spongy material (maybe a small piece of an air filter) tied up at the end of the hose might be good. It will soak up some oil vapor and prevent moisture coming in when the bike cools down.

Figured I'd rig something up.

Edited February 23, 201412 yr by wallrat

No that's not right

There is no crankcase vent hose on a. 2 stroke, that part is sealed tight against the atmosphere and if it were vented the bike wouldn't even start

it's a transmission vent hose

Yes, I called it a gearbox (a transmission) there is no such thing as venting a crankcase on a 2stroke, it relies on its sealing for building compression. The port induction of the distant past had the piston block the intake while it was going down, the reeds are a form of a one way valve, and the rotaries had the crankcase venting at part of the stroke and then shutting the rest of the 2 strokes through a rotating disk going past a window.

The gear boxes on 2 strokes are isolated from the crank, unlike modern 4stroke motorcycles which use the same oil in crankcase and gearbox. Although on some of them when main crankseals go (depending on the arrangement) compressed air escapes to the gear box, sometimes pumping the oil out of it. They usually don't run well enough or long enough to cause tranny damage. On some water cooled the oil is separated from the water side of the pump by a bearing and seal system. When that goes bad the bearing goes bad as well and steam/coolant pumps into the tranny. Which is one reason mostly 2 stroke street bikes will have that vent pointing away from the rear tire, for obvious reasons.