Coolant Leak / Rough Engine

[Bummer15]

Looking for some help with a unique issue. I have a 1981 GL 1100 that I bought as a project. 39,000 miles on the engine and has been sitting for about 15 years. I’ve been through all the steps to get it running. Rebuilt the carbs, replace the starter, fuel pump, water pump, and gaskets. Started the engine on the frame a couple of days ago and it ran beautiful for about five minutes. As soon as it got hot, it started blowing white smoke. More like steam. I find it hard to believe both head gaskets are bad but I know it’s a possibility. I let the bike cool down, started it again and it ran beautiful for about five minutes. It seems as soon as the thermostat opens up the bike starts running rough and blows white smoke. Before I change both head gaskets, is there something else that’s common to both sides that would allow coolant to enter all four cylinders? I did have the transmission cover off. I replaced all of the O-rings in that assembly with new. Not sure if a mistake there would cause this issue?
One other thing I noticed, when I removed the timing cover, One of the holes for the special bolts that hold the timing cover on started dripping water. I’ve included an image of that location. My guess, it’s not supposed to do that? Maybe someone has drilled into the water jacket? If so, could that be the issue? Any help is appreciated. Thanks much!

[Rambozo]

You could do a cylinder leakdown test to confirm.

[Track T 2411]

+1 on the leak down (or maybe just a compression) test.
On the cover bolt leak, I've never heard of that issue, but the thermostat housing and upper radiator house is just above it... leaks often show farther away from where they originate. Just sayin'...

[Bummer15]

Good advice. I’ll do the leak down test tonight. As far as the leak, I can watch the water drip from the bolt hole. I was unable to post a video of it.