What the guys are saying is if/when the rad. cap gets "gunky", your system won't pressurize as it normally should. You can test this by going for a ride, getting it hot, then check the hoses for firmness. You might want to check hoses when cold to feel how mushy they are with zero psi, first. Anyway, if they're firm when warm/hot, your cap is probably good.
For leaks, the first place I'd feel for is the upper rad. hose. You can just touch that connection to the radiator up thru the left air outlet on the fairing. I've seen/felt this joint moist a few times on my ST2. I even found a new bike in the shop (back in the day) doing its little piddle on the dealer's carpet. (Naughty Duc!)
I'm 90% sure it sill be a minor leak, if/when you find it.
Oh, this "leak"... I've seen the bike drip a few drops overnight, mostly during cold weather, and when the bike is not being used. Then totally go away, when the bike is used routinely...