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Discussion Starter · #1 ·
I’ve been having a problem with my CB300F back brake dragging and making sounds as I come to a stop or rolling it around the garage.
For lack of a better description it’s more of a low pitched pulsing whine as opposed to a high pitched squeal. The slower i go, the slower the pulsing. I can even get it to do it constantly if I rock it back and forth in certain places in the wheel rotation.
I’ve narrowed it down to the back brake because i can squeeze the pad away from the disc with my hand and it stops.

Here are a couple more details:
The bike has around 1800 miles on it and it’s 7 months old. The problem started a few hundred miles ago.

At about 1000 miles I tightened up the chain a bit which I’d never done before but I think I got it right with the slack and the back wheel is aligned. For the alignment the marks on the swing arm match up side to side and I’ve measured from the swing arm pivot caps to the back axle and it’s within 1mm. The chain has at least 1" play in it.

I thought maybe the pads were glazed so I took out the pads and gave them a quick sanding and I’ve taken a scotch brite pad to the back disc. I favor the front brake and I thought i might not be using enough back brake or too lightly so it glazed up but it still does it.

That’s pretty much it, i don’t think it’s dangerous but it’s pretty annoying.
Any ideas? does anyone else have this issue?
 

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A stone caught in the brake caliper can cause a squealing sound as it rubs on the disc rotor but as you've had the pads out that would have dislodged it.
Do you have ABS or not?
 

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making sounds at certain points of rotation when
youve ruled out pads, sounds like uneven wheel
thus disc movement.. if youve checked wheel
alignment carefully then next suspect is disc
rotor.. check for warping or gouging of disc..

general possibility uneven caliper action
or sticking or ? check calipers..

having checked obvious things
and only 7mths old, get it to
a honda tech, under warranty..
 

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Discussion Starter · #6 ·
I'm going to look more carefully at the caliper and make sure it's moving freely. I messed about with it some and it seems to move, but i'm sure how much is expected.
I also thought about the disc being warped or having a high spot on it and i can't really see anything in the wear pattern but like i said, i don't really hammer on the back brake so there isn't much wear yet. I thought maybe if it was a high spot using the back brake more might wear it down.. dunno, but I'm going to give that a try too.
I'll try a couple more things and if it's still acting up I'll take it to the dealer as suggested.
Either way i'll let you know how it turns out.
 

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not thinking of high spots, but symptoms as you
describe them could relate to warped disc [rotor]
unlikely,, given your riding..
other cause for that could be wheel/axle
alignment.. not saying you havnt done a good
job with it, just that alignment fits symptoms..
[id be loosening everything and doing it again
being sure to free up everything before
tightening axle, and not, overtightening..

otherwise caliper and movement of pad
could fit your sounds/symptoms..

finally, wouldnt hurt to have someone else
move the bike as to cause those noises
and you keep a good ear out for exactly
where its coming from,, especially
everywhere other than brakes
[eg countershaft sprocket etc]..

seems a no brainer aside from the fun of it,
to have it seen to by an expert honda tech
under warranty..
 

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Discussion Starter · #8 ·
Yesterday i spent taking Shisosin's advice to loosen everything up and start over with the alignment. I pulled the swingarm pivot caps and measured directly from the the center of the swingarm to the rear axles instead of using the caps as center. It's actually still kind of hard to tell where exactly the center of the bolts and nuts are but i did it a bunch of times. It appears that the right side of the bike was somewhere around 2mm's off from the left side of the bike. i adjusted both sides till i was pretty confident i had it perfect.. double and triple checked it, tapped the axles back tight to the swingarm with a dead blow hammer and tightened it up.

The sound was gone.

I was pretty surprised by the tight tolerance for this, 2mm's didn't seem like much. it literally was 2 bolt head faces off, so i guess a quarter of a turn off from one side to the other.
When you guys align the back do you have to get such high degree of accuracy? and if so do you have any tips to make it easier?
 

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When you guys align the back do you have to get such high degree of accuracy? and if so do you have any tips to make it easier?
I just go off the vertical marks on the adjustment plate and they seem to do the job even tho i doubt their true accuracy. Haven't had any rear brake issues so haven't felt the need to get things more precise. Glad you got it sorted.
 
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