i see. so do you think that if i rev the bike close to redline for some time while standing and looking at the reservoir i would be able to see the bubbles come up if the gasket it letting gas through?
ALSO: the fact that i sometimes smell the faint odor of burned (sweet) coolant come up from under the cluster/ triple tree area when i start it every few days... could mean that the system could potentially be taking up air by vacuum through the leak?
No, DO NOT do that. That would be retarded. You'll do more engine damage revving it up like that without a load on it. I don't think you're understanding really how this all works. The bubbles are a result of the boiling. The boiling is a result of the head gasket. Two separate events have to happen here. You have to get the cylinder pressure up first, which lets air into the system. You then have to heat the coolant to near boiling. You're not going to be able to get that to happen by revving the shit out of the bike in the garage and standing next to it. It's not a constant stream of bubbles or an immediate effect. It's a build up of events that feed each other. And with the motor unloaded, the cylinder pressure will be lower than you want to test this fully.
Replace the cap and see how that goes. Stop worrying about the bigger problems until you eliminate the smaller, easier issues. Don't get ahead of yourself.
Likely the coolant smell is from the reservoir bottle overflowing and leaking onto the headers which gets burned off. Yes, you could have a pin hole leak in the radiator and it would cause this same issue. But there would be more evidence of a leak like that as you'd smell it more often than not. Again, the cap first as it's easy and prone to failure. From there, you could do a UV die leak detection of the fluid to see if it's leaking. After that, the troubleshooting gets more costly and more difficult.