Wednesday, July 17, 2019

Layers

 This isn't about layers like an onion or how to dress in cold weather. The layers I'm talking about today are layers of noise. Not a mix of instruments in an orchestra creating wonderful music but an annoying sound masking an annoying sound masking an annoying sound and so on. On a solid mount v-twin motorcycle, especially of the Harley variety, you get lots of vibration and that equals noise. My Sportster is one such animal and while it won't shake the bar out of your hand, it will buzz hard enough that loc-tite is needed on most of the hardware.


 As reported, I've been riding this beast a lot lately and all that noise has been making me crazy. I fix one thing only to hear something else. I finally figured out that the biggest noise I had was a combo platter of noises all stacked on top of each other like a hero sandwich.



 I was tooling down the hiway and at a certain rpm a big buzz erupted. I set my hand on the center console and the buzz quieted. Huh, that seems like a simple fix and the next time I had a chance I added a plastic trim strip around the console and tightened the screws down better. Turns out that was just the top layer of noise because on my test flight I got a muted version of the same noise. I squeezed my knees against the tank and it subdued the vibes so remounting the tank went on my to-do list.


 Remounting the tank went exactly opposite of how one would think it should go. When I first put it on there I had used some rubber on the front mount to soak up the vibes. This time I replaced the rubber with aluminum tube shims and made the mount solid. Guess what. That quieted down the tank buzz and I did a full tank test ride so I know its not a layer of noise related to fuel level. It sounded good from full to dang near empty. It did something else. It allowed me to hear another annoyance that was going on. It was a noise not related to engine speed but rather bumps in the road. You'd think I could just park the bike and start wiggling things to figure out what was loose. Wrong. Nothing appeared loose until one day I was at a buddys house. We were standing next to the bike shootin the shit when I kicked the front tire. Thats the noise! I did it a few more times and realized it was the brake pad rattling in the caliper. During my next maintenance session at home I disassembled the caliper and rebent the spring to put more tension on the floating pad. This helped a little with the noise and a lot with my sanity. I was relieved to have removed another layer of noise but alas it also revealed the fact that there was at least one more noise related to hitting a bump.



 The noise sounded like it was coming from the front until on one ride when I leaned way back and hung my head down low. I could hear that the noise was in fact coming from the rear and was most likely chain slap. I knew the chain was on the loose side and adjusting it was on the list but I didn't think it was loose enough to slap the chain guard or engine case. I think the reason its so sensitive to adjustment may be cuz this is a conversion. The engine was belt drive and the bike was chain. When that engine was swapped into this frame I put a gear on in place of the belt pulley. I'm not sure if the diameter of that gear makes clearance an issue but after the chain adjustment, my noise went away. Its not the last layer of noise but its the last one I need to fix to keep my sanity. Besides the rush of the wind and the rumble of the pipes I have a very mellow driveline hum that only is audible under load. Maybe something from the transmission? Maybe a wheel bearing? Maybe its just the sound all these pieces make when acting upon each other. No matter because for now I'm just gonna enjoy the peace and quiet that a big bore sportster offers.

Later.

1 comment:

  1. Nodding my head in agreement all the way through. In a car ignorance is bliss - you don't hear anything (or at least not much). On the bike it's different. What's that noise? Is it new? Should I worry? Constantly chasing down various rattles, squeeks, and whines.

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