Crankcase vent hose popped off

[Anonymous]

Hey GSR,

So, I was out riding 2-up with my girlfriend tonight and I got on it a little bit going down a long straight road. I turned off into some twisties and noticed the bike was surging, stalling at stop signs, etc.

A couple miles down the road I pull over to hit up an ATM and I decide to investigate. I notice some steam that smells oily coming from near the airbox, and figure out it's the crankcase vent hose that popped off. I lift the tank and sure enough, it was off. I put it back on and all my problems were solved.

So, my question is, what made it pop off? Under heavy acceleration, does this hose build up positive pressure, or is there negative pressure? If it builds up positive pressure then I guess it could pop off from that, but I'm almost a little skeptical. Is this indicative of worn rings and hella blowby? Could the engine have moved in the (rubber?) mounts from the torsion and pulled it off?

If any of you all have noticed this behavior on your GS I'd like to swap notes. I'm going to get a new clamp for this hose - all the stock spring clamps on the GK are pretty shabby, I had some petcock problems before because of that. But still, for that hose to pop off like that? It seems weird.

[Anonymous]

The hose that popped off could be plugged causing a preasure buildup inside the engine, blowing the hose off of its fitting. Anything that leaks past the rings (blow by) and or valve seals and there is always something leaking by, ends up exiting the engine via that hose. If the engine is "blowing by" excessively, it could exceed the capacity of the hose or plug it up with muck resulting in the hose being blown off. Short runs that never really heat up the oil so that it can boil off the water its collects from the blowby create lots of gunk. The stuff that blows by the pistons is loaded with H20 from the combustion process. Checking what comes out of that hose while the engine is under real life load could be tricky. Perhaps run a longer hose to where you could watch it exit into the air instead of into the air box and go for a ride warming the engine and its oil to running temp and check the hose output under full load conditions. Remember that if the oil is "wet" it will steam for a while until the oil is dry. I'll bet that it just fell off and there is nothing wrong otherwise you would have noticed oil consumption and smoking exhaust, lets hope.

[Anonymous]

Well, it was definitely emitting vapor of some kind, even after a good 20 mile ride. Of course, that was with the bike in neutral and just a little revving without a load. Is that normal?

Exhaust is peachy, but the bike does lose oil somewhere. I know I have a leaking chain tensioner (who doesn't at some point, right?) so I've figured it must be due to that thing. Are you saying that with blowby I'll burn off oil somewhere?

Interesting what you mentioned about short runs. I use the bike for a lot of short runs - sometimes I use it like an 1100cc scooter, and I know that's a shame but with those saddlebags it's good for trips to the supermarket and a lot more reliable than my Toyota. I'll take the hose off and check it for blockage.

[Detman101]

I ran mine to the rear of the bike and put a crankcase filter on it.
When the bike warms up and it starts venting you can see it.
I call it my little tea-kettle. It gives the rear light an eerie glow at night.





Dm of mD