Engine Leak / Blown Gasket 83 KZ750 Spectre

Hi, I got an 83 KZ750 spectre with about 12k miles.

History of the bike: Bought it form a guy that said he got it from the original owner. Said bike sad for a month or so.

My initial problems with the bike: Won't idle on choke. It's always been like that. Run a gas tank with sea foam and it seemed like it was getting better, and would idle without the choke on...but it would idle rough. Then a couple of days later it would only idle with the choke on again.

I checked sparked plugs, and changed the oil.

I was about to drain the gas tank so I can to remove the air filter, clean the air filter, and possibly remove the carbs and clean the carbs.

When I drained the tank, I had let it idle for about 20 minutes. That's when I noticed some faint smoke on the left side of the engine. I stopped the bike, and noticed that the gasket in the middle of the engine has a big gap in it. I believe the leak has always been there, it's just now that I'm noticing it.

So I'm wondering what to do. Should I pull the top half and replace the gasket, or is the engine overheating causing the gasket to blow for some reason, and if there are other underlying problems I should look at. Here is a pic of the leak and gap in the gasket.

letting it idle for 20 minutes without fanning it (I assume it is air cooled)is not good...could (will) cause all sorts of problems.

The arrow is pointing to the head gasket. Ditto on never idle it for more than a few minutes unless you set up a large floor fan to blow air on the engine. I have seen head gaskets seep oil, I would check compression cold and hot before I tore into the engine. If compression is OK, run it.

There is an oil pipe running from the cylinder up to the head right in that area so it's possible you could be getting some leakage from it.

Maybe check the tightness of the cylinder/head bolts with a torque wrench? If they're loose, tighten down to spec and see if it compresses the seal.