I've got a 2000 Harley Road King Classic with 26,000 miles. I fired it up this spring to find that it was making some fairly ugly noises on the first trip around the block. The most offensive of the noises was, what I'd call a knocking sound similar to if you were to bang your knuckles on a mostly empty tank.

After doing just a little riding, I found that I could replicate it very predictably by going about 35 MPH and letting go of the throttle ... best if I were on a slight decline (so as to hear it longer). If I touch the front break the noise instantly goes away. For the past few years, the bike had [on occasion] sounded a bit like an old car with some squeaks and rattles.

I took it into the dealership for a 5,000 miles maintenance ($310 ... ugh) and they said that they found and eliminated quite a few noises. They said they adjusted a heat shield (but weren't completely happy with that adjustment), found that the jiffy stand stopper was missing, and removed the keys from the front leather pouch and found/fixed all noises they could. I wont lie, when I picked it up i immediately felt as though the bike was "tighter" ... like they took 10 years off it. No more old car sound!

When I rode about a block away from the dealership, the knocking was back (and I swear, louder). It happens when I am rolling to the stop (or breaking slowly but NOT using the front break). It is in sync with the engine rumble. When I touch the front break -even just lightly- the sound instantly disappears. It doesn't happen all the time (like things need to warm up first) but when it does start, it will continue until I stop the bike.

Here's my speculation:
I figure that the only thing that could have changed during the winter is that some rubber bit aged and now some bit of metal is a bit closer to some other bit of metal and knocking together during the right condition. I believe that when the bike is slowing without using the front break that the motor is leaning forward or exercising an aging motor mount and bringing the engine into contact with something immovable (tank?).

The tech didn't notice anything during the road test following the maintenance, but I'm guessing he wasn't as methodical in his evaluation of the ride as I was. He probably used the front break each time he wanted to slow the bike ... which doesn't reproduce the problem. Ideally I'd take it back to them and ask him to road test it again ... but I'm not sure if I'll get a chance so I'm trying to think it through myself. I'm actually wondering if I could get it to work by simply parking nose first on a hill and rev'ing the engine. (Probably would need an assistant for that.)

Here's my question:

1. What are the common causes of knocking/banging?
2. When do motor mounts go bad?
3. Anyone have any tips for me in figuring this out?