Re: Clunking noise

[Neil Halbert <halbert@xxxxxxx>]

"Anderson, Neil G" wrote:

> Jonathan,
>
> About the clunking noise you mentioned from your** front end: three
> possibilities, from looking at all the list traffic over the last couple of
> months:

Sorry, I didn't describe it well. A better term to start with would have been
buzz or rhythmic vibration and not a noise. You don't "hear" with your ears.
The reason I say knock/clunk is that is quite regular and strong. It is not a
knock like, on throttle klunk, off throttle
klunk. Which I would attribute to a head bearing.  It's regular and felt
through the bars and pegs.

It's almost feels like a tire bubble or one going flat, very regular.
Particularly  in 4th, 5th and 6th gears, getting more pronounced as you go up.
It makes me wonder about the layout of the shafts and gears in the
transmission. Do they (4,5,6 or just 5,6) share a common shaft or such? Also,
it is not there from the get go. It usually takes 5-10 miles for it to develop,
stating off softly and getting stronger. It is hard to say if it changes
frequency, as in down shifting but then again the difference between 5th and
6th isn't that great.

It seems like it may be a heat or a transmission thing. One being common to a
bearing set in the transmission or the other being a heat
build up causing something to distort or become softer.

When you clutch it at speed and rev the motor it doesn't seem to be noticeable
over the "normal" engine vibrations or at least not being transferred to the
frame. Which would seem to rule out tire problems.

Now may be something with the "cush" drive gear? I have heard that the drive
gear has some rubber mounted side plates that are to smooth out the chain's
ride. The side plates ride on these so the teeth only engage the rollers on the
flats and not in the pit of the tooth.

This could fit the profile. There would be heat buildup and change in
compliance. It could also explain why chain tension seems to vary it some. But
why would too loose a chain cause the same feeling to appear? Does not vary
greatly with gear shift. A more direct drive in 5th and 6th transferring it
more directly?

An imbalance in injectors/throttle bodies? It is a bit rough at idle.

I'm going to try and vary the chain tension a bit and see what effect it has.
The other thing will be to give it to shop for a bit and have them do some
miles on it again.


> 1. Loose headstock bearing; put the bike up on the centre stand, get someone
> to lean on the grab rail to get the front wheel up and try pushing the front
> axle forwards & backwards to see if there is movement in the head bearing.
> Or something like that.
>
> 2. Loose something - brake pads?  Unlikely

Agreed.

> 3. It's so cold that your wrists have frozen and your shoulder joints need
> to be oiled.

Shoulders, back, hips............. It's getting so bad it is hard to hear the
wind over all the noise.

>
> Neil
> ** OK, the bike's front end

- --
                                                    _
Neil Halbert                  _/_/_/ _/   _/  _/_/ '_) EMC Corporation
email: halbert@xxxxxxx       _/--/  _/ -'_/ _/     /__ 171 South Street
voice: (508) 435-1000 x1232 _/_/_/ _/   _/  _/_/       Hopkinton, MA 01748




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