Air filter not secured 100%

Hey there. i'm new to having a bike and decided to do a little bit of simple maintenance.

so i was taking out my air filter to blow it out, and i noticed the air cleaner cap was cracked making it not able to securely screw into the threads. i didn't think much of this; the person who i bought the bike off of rode it for years and never had a problem. so i go about my business with it, and then i pulled out the inlet pipe holder and saw that the holder gasket was completely soaked in what smelled like gas, and it proceeded to crumble once i touched it.

I'm wondering, is it crucial to have that gasket and to have the cap tightly screwed down to ensure working order?

thanks.

What bike? It seems like a missing gasket & cracked cap might cause a vacuum leak. The cap for the 81 650 was still available at the dealer as of a year or two ago. If you get a new cap, tighten it snug but don't overdo it - there's no need to crank it down.

Any air not filtered will cause wear to the engine over time.Probably affects gas mileage and general performance.

sorry about not mentioning the bike: 81 kz750.

so it seems i should get a new cap for it then. also though, the cap does screw on w/o the filter in place. the previous owner said he didn't replace the filter at any time, so could it be the cap doesn't screw on tight due to the crack in it, or the filter itself?