So I've been feeling a little extra vibration recently and sometimes when I hit a big bump in the road, it sounds like the entire engine (or something near the engine) is lifting up and slamming back down.

Obviously I think this is weird so I take a gander at all my mounting points because clearly the engine should look like it's about to fall out, right? I can't see any obvious signs of damage or wear, but frankly I don't know what the motor mount should look like after 11k miles...local shop says it's worn and I should replace, but a group of old timers hanging out in front of the MoCo said the shop is crazy and my motor mount is fine. Thoughts? What else could cause this slamming/shifting of the engine?

 

Not much visual difference between a good one and a bad one. Most obvious sign is if there is a gap between the centre of the mount where it bolts to the frame and the motor bracket. If its sagged there will be no gap. A good one will have a gap that alows the motor to move without bottoming out.
https://www.hdforums.com/forum/dyna-...de-owners.html

 

Yank up and down on your gas tank. The bolts might be loose on the tank making a banging sound.

 

AHHH Where to start !!! Could be your gas tank like PENN says could be a front end clunk, could be the motor mounts .Grab some wrenches and give a once over do a search here for a motor mount shim.

 

Don't depend on feel to see if your tank bolts are loose. you need to put a wrench on it, even a 1/4 turn can make the difference.
You didn't say how many miles on your bike (or for that matter, what year/model of bike you have), but I've seen where the front motor mount won't last 7000 miles. Like mine.
You can see if the rubber is all torn up, or if you can get a small jack under the motor and put take some of the load off, you can see if the motor has a lot of movement or not.

 

If it is worn out, It's simple as hell to replace yourself.

 

2005 FXDL with 11k miles. Tank bolts are all on tight, how difficult is it to replace the motor mount myself? I have tools but limited space and no bike lift...a bottle jack is about the best I can do

 

Thats all you need. Support the weight of the motor on the bottle jack. Then its two front frame bolts and two in the motor mount bracket. Takes half an hour. A bit longer if you have an oil cooler. You can do it on the jiffy stand.

 

Am I wrong but a sagging front motor mount wont make a banging sound like the motor is falling out with only 11000 miles will it?

 

if your bike is a 2005 the rubber in the mount could have deteriorated over time.