Rubber bits are rubber. They flex and wiggle when brand new. They don't get "broken in", though they do break down with time.
Except, somehow, when mounted on a Harley. I've read about this, didn't really believe it. Until I owned a Harley and found myself experiencing this rubber impossibility.
Example #1. Lets use my front motor mount. Thoroughly destroyed, leaving my engine to flap around. I was slow to realize the mount was destroyed because I thought all Harley engines flapped around. The damage was subtle (at least to me), but once I figured it out, I replaced it. While the new mount reduced the flapping, it still left me nearly blind at traffic lights.
But, over the course of many hundreds of miles, things got progressively calmer. To where the bike merely vibrates a bit at idle. I can see! I don't shut down the engine to wait out red lights. And, I swear, the engine flaps around even less than when I put the mounts on in the first place. In fact, it barely wiggles now.
How the heck does a rubber motor mount "break in"?
Example #2. Tailpipe bushings. The ends of my absurdly heavy tailpipes hang from a rubber bushing. Being a Harley, things wiggle, so the mufflers have to slide in these bushings. It's a weird tuning game that means when they are too worn, or too tight, the mufflers vibrate the bike like an exhaust pipe touching the frame.
Put new ones on my bike because they are cheap, and having read about this phenomena, I was curious. At first I shimmed them, and that was a horrible mistake. The bike flat out tickled me, making riding an embarrassingly giggly event. Took the shims out and while it was an improvement over the old worn bushings, it wasn't much. But again, many hundreds of miles later and darned if the bike has no tickle in the floorboards, and is even quieter than when I put them on in the spring. Again, mysteriously breaking in rubber bits?
This is a strange bike. Perhaps all Harley are strange bikes. Delightful, to me, but strange.
