For those that work on their own bikes or take them to a stealer.
Do not try to block the seal from coming out or you could cause serious damage as it acts like a relief valve.
Here is a copy of a post that I have been posting for at least seven years.
This is about the hose behind the bottom of the airbox.
I do this every time I get my X back from the stealer
If the air-box is ever removed by you or the stealer, there is a possibility the breather hose for the crankcase could get pinched. (This hose is the pressure relief for the crankcase, so pressure dose not build up.)You could have a pinched hose.
If it is pinched, pressure will build up in the crankcase and blow the seal out around the shifter lever.
If this seal is ever blown out, you can put it back in by tapping it back in.
A simple way to check is:
Take the air cleaner cover off.
Take the dipstick out and lay a 3x3 single layer of tissue paper over the opening.
Take a common drinking straw and hold it over the smaller hole in the air-box, (the one that sticks out), and give it a puff of air. If it blows the tissue off, you’re OK. If not, the hose is pinched behind the air-box.
If the hose is kinked or blocked how long does it take before you start leaking oil as you're riding. As the engine warms up the oil expands and build up pressure in the crankcase and if the hose is pinched it build up enough pressure to blow the seal out around the shift lever. You just have to put it back in. I have heard of some that have driven many miles without any damage except for a mess to clean up and a dangerous oil covered rear tire.
Donut, Doug,Coloma, Mi.