Air from oil fill hole when engine running

[fastenuf4u]

I never removed the oil fill plug while the bike was running before but I just did after putting on a heavier flywheel weight. Is it normal for their to be air "puffing" out of the hole, almost seems like blowby. This could have been happening for a long time but I wouldn't know because like I said above I never took it off. Thanks for any replies, and corrective actions if it shouldn't be doing that. Thanks.

[JetPilotAlabama]

Leave it on and it will not blow.

[fastenuf4u]

Leave it on and it will not blow.

I have no problem doing that as long as nothing is wrong that could lead to a problem down the road. ? Thanks.

[grayracer513]

Entirely normal. The piston displaces 450cc underneath itself as well as on the top. That's one reason you need a breather tube.