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Light Knock From Gearbox #704872
08/13/17 3:08 pm
08/13/17 3:08 pm
Joined: Oct 2003
Posts: 3,607
Emsworth, sunny south of Engla...
D
dave jones Offline OP
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dave jones  Offline OP
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Joined: Oct 2003
Posts: 3,607
Emsworth, sunny south of Engla...
Thriumph TR6R 1967 I was adjusting my back brake today with the bike on the main stand, in neutral, and noticed that when I turn of the back wheel in the forward direction there is a light knocking sound from the gearbox. For every turn of the rear wheel there are approx three knocks. It sounds like knocking one's knuckle on a wooden box. Not very loud. It doesn't do it if I rotate the wheel backwards. What could this be? I tried taking the slack out and also moving the chain sideways with my other hand as I turned but it still did it. Could it be a tooth on the gearbox sprocket, loose gearbox sprocket or maybe a high gear tooth?

Thanks
Dave

Last edited by dave jones; 08/13/17 3:15 pm.
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Re: Light Knock From Gearbox [Re: dave jones] #704878
08/13/17 3:52 pm
08/13/17 3:52 pm
Joined: Dec 2004
Posts: 9,377
Scotland
kommando Online content
BritBike Forum member
kommando  Online Content
BritBike Forum member
Joined: Dec 2004
Posts: 9,377
Scotland
Number of teeth on gearbox sprocket vs rear wheel, what is the ratio on your bike, should be close to 19 to 46 = 2.4 ish , could be related to gearbox sprocket on one tooth.

Re: Light Knock From Gearbox [Re: dave jones] #704887
08/13/17 4:52 pm
08/13/17 4:52 pm
Joined: Oct 2003
Posts: 3,607
Emsworth, sunny south of Engla...
D
dave jones Offline OP
BritBike Forum member
dave jones  Offline OP
BritBike Forum member
D
Joined: Oct 2003
Posts: 3,607
Emsworth, sunny south of Engla...
It has normal gearing and is 19 and 46 as you say. I had just got back from a ride when I noticed it and prefered a cup of tea to tinkering so will look into it further later.

Dave

Re: Light Knock From Gearbox [Re: dave jones] #704900
08/13/17 6:49 pm
08/13/17 6:49 pm
Joined: Apr 2005
Posts: 65
Tampa FL USA
S
Sam Offline
BritBike Forum member
Sam  Offline
BritBike Forum member
S
Joined: Apr 2005
Posts: 65
Tampa FL USA
With the bike on the center stand lean it over to the left and turn the rear wheel. If it still makes a knocking noise lean the bike over to the right and turn the wheel, is the noise still there? If the noise goes away you might have a shifter fork ring that has somehow fallen off the shifter fork. This usually happens upon assembling the transmission and it's not noticed until the rider detects a sloppy shifting issue and or a noise like you are hearing. If the knocking doesn't go away you have other issues.

Re: Light Knock From Gearbox [Re: dave jones] #704947
08/14/17 7:39 am
08/14/17 7:39 am
Joined: Oct 2003
Posts: 3,607
Emsworth, sunny south of Engla...
D
dave jones Offline OP
BritBike Forum member
dave jones  Offline OP
BritBike Forum member
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Joined: Oct 2003
Posts: 3,607
Emsworth, sunny south of Engla...
I went back out to the bike later when it had cooled down and it didn't do it anymore. I wonder if it is some clearance problem somewhere. I suspect that it may have always done this without me noticing. When I lube the chain when the bike is still hot after a run I spin the wheel backwards so wouldn't notice it! Also, I tend to normally check the brakes when the bike is cold. Will check into this again during the week.

Dave

Re: Light Knock From Gearbox [Re: dave jones] #705060
08/15/17 1:08 am
08/15/17 1:08 am
Joined: Oct 2003
Posts: 11,225
North Georgia, USA
RF Whatley Offline
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RF Whatley  Offline
BritBike Forum member
Joined: Oct 2003
Posts: 11,225
North Georgia, USA
I think your chain is wider than a standard old school chain. You may have to install your master link with the clip toward the gearbox instead of the primary.


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA
Re: Light Knock From Gearbox [Re: dave jones] #705067
08/15/17 1:36 am
08/15/17 1:36 am
Joined: Nov 2008
Posts: 2,799
Bishop, Calif.
D
desco Offline

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desco  Offline

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Joined: Nov 2008
Posts: 2,799
Bishop, Calif.
Whatley
How do you remember all this stuff? I just found my copy of Healy's "Tech tips". At least 35 years old, spiral bound, a lot of it eligible due to the poor copying technology of the day. And you were a contributor.


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
Re: Light Knock From Gearbox [Re: dave jones] #705120
08/15/17 3:15 pm
08/15/17 3:15 pm
Joined: Oct 2003
Posts: 11,225
North Georgia, USA
RF Whatley Offline
BritBike Forum member
RF Whatley  Offline
BritBike Forum member
Joined: Oct 2003
Posts: 11,225
North Georgia, USA
That was probably back when I had hair !

Been doing this way too long ! I was the tech editor for the TOMCC mag Nacelle in the mid-70's. I had to laugh. Something about the Brits sending their questions about their Brit motorcycles to the USA for answers.

laughing


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA
Re: Light Knock From Gearbox [Re: RF Whatley] #705128
08/15/17 4:17 pm
08/15/17 4:17 pm
Joined: Oct 2003
Posts: 3,607
Emsworth, sunny south of Engla...
D
dave jones Offline OP
BritBike Forum member
dave jones  Offline OP
BritBike Forum member
D
Joined: Oct 2003
Posts: 3,607
Emsworth, sunny south of Engla...
The knock is too frequent to be the split link.

Dave


Moderated by  John Healy 


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