I don't tear into motors and do valve jobs, swap pistons, hone cylinders, and etc. I have been riding motorcycles for over 30 years. I am a farm boy with experience trading and running tractors, and I've had over a dozen different motorcycles. I've run a lot of stuff, but I'm no engineer or mechanic. I have done valve adjustments on other bikes. I've done clutches, too; but every time is like the first time! So, take what I'm about to say w/ that in mind.
My opinion is that this is an inherently noisy motor. This is Kawasaki's first production v-twin! When this was designed back in the 80's the goals of the project were different than they are today. Kawasaki seemed to want a powerful, efficient, and low-maintenance bike. They were largely very successful. The sound of the motor wasn't really top priority as far as design goals. I don't think that "Harley's formula" for success was as well understood at that time--certainly not by the Japanese.
I think there are a couple of things you *can* do:
- Keep an eye on the drain oil at oil-change time. If you're seeing large pieces of metal, rubber, or plastic that's bad!
- Get a mechanic's stethoscope, so you can pin-point the location of the noises that you're hearing. It might give you some piece of mind or allow you to do further research. Likely it will let you eliminate one thing or another. Of course may make your anxiety worse!
- Get a louder exhaust? Yeah, I know that doesn't really fix anything, but what you don't hear won't bother you?
Really, it comes down to your needs and expectations. I use mine primarily for commuting back and forth to work. If something would happen to it, I'd get a ride home and go recover it with my trailer. I'd be inconvenienced, sure; but it's not like it's gonna ruin my vacation, trip, what have you. You just don't hear about these motors grenading all over the place left and right, so I'd say don't worry about it.
I recently got back from a 600 mile weekend, so it's not that I wouldn't trust it, and yes--mine has some undiagnosed noises at times too. I'm running one MCCT, and one OEM cam-chain tensioner. I'm planning to swap out the other tensioner as soon as I get one made up, but I'm just kind of ignoring the noises for now. My plan is to continue ignoring the noises if they don't go away after that. . . .
If it bothers you, and you can afford it, there are lots of other bikes out there--maybe it's time to try something else? At the end of the day nobody really needs a motorcycle. If it's giving you more stress than pleasure, it's probably time to find something that you'll enjoy! Chances are that it's not gonna be as much bike for the price, though.
When I was shopping for this bike, I was also thinking about the Yamaha (Star?) Bolt. I don't like sitting in traffic on an air-cooled (or really any!) motorcycle, but I really don't like air-cooled! Lots of people do it though, and I just don't hear about that many problems. I'm pretty sure it's just my issue. At the time I'd just gotten a Kawasaki 454 for my son, and I was kind of jazzed about having "matching" bikes. That didn't really work out, but it was a factor in my purchasing decisions. . . . Maybe something like the Bolt would catch your eye?