Rattling on top end back cylider

The only thing under the rocker boxes is the rockers and the upper part of the heads with the valve springs. Getting to this area is not that difficult.

Remove the fuel tank and seat. Then, remove the six bolts that holt the top and middle rocker box covers on. Now, you're at the rocker plate with the rocker arms in it. You can also see the tops of the valve springs. Look and see if there is anything that might be causing your noise.

Now, keep in mind that a Harley engine is of an old design. It is a pushrod type engine with rocker arms that open and close the valves. They are going to make a little noise. Now, if you're having to get close to the rocker box to hear the noise, it's probably nothing to worry about. But, if you can hear the noise stand away from the bike a few feet, you may have a problem. But most things that might break or come loose under the rocker box will usually effect the way the engine runs.

Also, you could have an exhaust leak. It makes a "tick, tick, tick" type noise. Tighten the nuts on the two studs snugly but don't break them off.

Good Luck
Steve