My bike slowly developed a random semi-rhythmic light dull thudding. I can feel it mostly in my seat and it is always at cruising speed and mid range RPMs. It almost feels like you are hitting a bunch of tiny bumps in the road that are not actually there. Another symptom that started a few days ago is when I am going around corners very slowly in 1st gear my back tire feels squirmy likes it's sliding left to right. Going around corners at higher speeds feels normal.

Here are some things that I have checked.
1: Tire condition, they seem to be fine (Metzler 880)
2: Tire pressure, I have bumped it from 36r/30f to 44r/40f which helped with the thudding but not with the squirmy-ness.
3: I have gone through and checked for any loose bolts, found nothing
4: When I shake the bike on the stand I see nothing shifting or moving.

My thought now is maybe it's the front motor mount? My bars shake like a mf'er at idle. 2011 Street Bob with 17.5K miles. Anybody have any thoughts about what may be causing this?

 

That sure sounds like a tire, a semi-rhythmic dull thudding. They may look alright, but that doesn't mean you didn't hit something and caused damage you can see or the tire cords are not separating. It's possible you tossed off a wheel weight but I doubt it. And a squirmy rear, not good.

Put the bike in a no ride condition, never play with your tires; everything you are is riding on them

As far as the bars, sounds like the rubber riser bushings are toasted. They're junk to start with and once they begin to deform the motion in the bars will increase. Poly or solid bushings; inexpensive, and a vast improvement over the HD rubber bushings. The front isolator could be going as well, as it deforms and contacts the engine bracket it will transfer the vibrations in to the rolling chassis and you'll see it certainly at idle.

The front isolator and the riser bushings are not difficult to change out, but it's that rhythmic thudding that I don't like. Check your tires carefully. Any issues losing air pressure? Any odd wear patterns on either the front or back? Not all tire damage is visible...

 

I checked the tires out and they have plenty of tread but I do see a little dry rotting in the treads. No pressure loss, every time I check them they are right where I left them.

Another point worth mentioning is that I have not felt the squirmy-ness right out of the gate, it's been after riding 30+ minutes each time it's happened.

Anyway, here is the front tire:


And the rear:


Close up of the dried out area:

 

Check your rear wheel bearings maybe?

 

Damn, that's another great idea as well

 

Them tyres look brand new, how come dry rot already, not normal, check year of manufature on sidewall, but for me it all points to a failed front motor mount, had exactly same feeling in my old wide glide, clunking was coming from engine slopping around once hot, and if you gonna change the engine mount, might as well get a Predator you will save cash, and ride will be more solid.

 

Just checked the service manual. Looks like something I've got the tools for and could do myself. Thanks!

 

While the wheel removed - verify it balanced

Also verify the rear in alignment

Ghost

 

Bike is new to me in March so I didn't know how old the tires were. I ran out and checked and the front is marked 1412 which is the 14th week of 2012 and the rear is 4711 so the 47th week of 2011. The bike is 2011 so I am guessing they are original?

Rear Stamp


Front Stamp

 

I will be honest, if it was me, them tyres would be gone and new rubber on, they look hard and dry, I reckon new tyres, new motor mount and you will be rocking and safe.