[Dgrblu]

2019 z force 800 trail. Twice now, once in July last year and again yesterday, since I purchased the bike, there has been oil spewed out of a tube that's wire tied at the top of the frame , below the cargo box. Oil on top of valve cover, cvt exit air tube, down frame, top of skid plate then dripping on to hauler deck. I thought it was engine oil but after wiping it up, took a smell which seems to be gear lube. I pulled the vent tube from the differential,  free flow not plugged, but the inside of the hose has no evidence of oil....
Any ideas or just a freak occurrence?  Thanks for the input.

[NMKawierider]

I have a theory but that's about all at this moment. First we have to understand that the vent is to releive pressure as it heats up and and expands the oil and cast as it all expands then allows air back in as it cools down and contracts. If there is nothing but the lube in it that expansion is limited to the amount of heat it's holding. However, if that lube contains something that continues to change from a liquid to a gas, like water, then the outflow will also be continuous until that material is all converted. It will also take oil particles up the tube with it and deposit it all over the place. This happens with guys that do a lot of mud and water riding all the time. But what else can cause oil to flow up the vent tube during normal operation and no water in the oil? Well, not much..however this is where a theory comes into play...and it only come from trying to understand why mine also did it once..or twice. Aside from overfilling the unit I believe a heat source can also cause continued expansion and smoking that leads to outflow of that vent. I say this only because several times in the last I have taken-off with the parking brake on and rode several miles in some cases until I smelled that..smell..you know, the one of "toasting brake pads". I know at that time the disk is at or near red hot...and it is affixed to the pinion yoke...and that leads straight into the case and oil. And for me both times I saw and smelled that 90W smell was after I had done that. And..the lube went dark in color right away as well. I can't prove it...but there is a hint of logic in it. So I would make sure my hand brake isn't set too tight or dragging in any way. Here's another thought...and it comes from my Kawasaki background. With then with wet brakes, when the pinion bearing retainer backs off it allows the pinion to ride or move forward and back on the ring gear. This either engages or not..the wet brake friction disks making then drag and heat..and toast the oil as well. For ours, if the pinion moves, it also moves the hand brake rotor...and that forces it against the pads in either direction. So...it will be hard to see if it has any movement but it's also worth checking. Ok, enough rambling