961 Commando primary gear noise engineering remedy

Hello everyone, I have owned a 961 Commando from new in 2016. When i received it it sounded like a guy hammering an anvil. So bad that I returned it to Norton who said they did some 'adjustments' but nothing worked so....... after a lot of head scratching and using my engineering knowledge and some work carried out by a couple of machine shops near , I engineered a remedy. I've decided to share that remedy after riding it for some miles.
Firstly I will explain why the primary gear literally 'hammers'., if it hasn't already been posted (please bear with me if it has). Simply the intermediate split anti-backlash gear can never work between two gears. This is a fact and can be confirmed by any reputable gear manufacturer. Anti-backlash gears can only work in one direction. So what did I do ? I managed to blag some spare gears (primary and intermediate anti-backlash) from a guy who held a lot of sympathy in Norton back in 2015/16. This gave me the opportunity to think and try solutions. Although the gear drive train will, never be super quiet (unlike my Triumph Bonneville America) my 961 is significantly quieter.
I have just stripped out the primary gear drive train to check all is okay and taken the opportunity to take photos . If any one is interested in what I have done then click on my thread and I continue this thread with what I tried...what failed and what worked over the next week or so.. with photos etc.

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stevejhome said:

Hello everyone, I have owned a 961 Commando from new in 2016. When i received it it sounded like a guy hammering an anvil. So bad that I returned it to Norton who said they did some 'adjustments' but nothing worked so....... after a lot of head scratching and using my engineering knowledge and some work carried out by a couple of machine shops near , I engineered a remedy. I've decided to share that remedy after riding it for some miles.
Firstly I will explain why the primary gear literally 'hammers'., if it hasn't already been posted (please bear with me if it has). Simply the intermediate split anti-backlash gear can never work between two gears. This is a fact and can be confirmed by any reputable gear manufacturer. Anti-backlash gears can only work in one direction. So what did I do ? I managed to blag some spare gears (primary and intermediate anti-backlash) from a guy who held a lot of sympathy in Norton back in 2015/16. This gave me the opportunity to think and try solutions. Although the gear drive train will, never be super quiet (unlike my Triumph Bonneville America) my 961 is significantly quieter.
I have just stripped out the primary gear drive train to check all is okay and taken the opportunity to take photos . If any one is interested in what I have done then click on my thread and I continue this thread with what I tried...what failed and what worked over the next week or so.. with photos etc.

Click to expand...

Welcome to the forum

Funnily enough I have spares as well, and have toyed with modifying an intermediate gear so that it sits deeper on the balance shaft and has a backlash gear on each side ( one for the drive gear and the other for the clutch), but I have no idea who could carry out the work.
So yes I would be very interested in your solution ( and I’m sure others too).

By the way, if you want to post images directly, you will need to join as a full (paying) member.

stevejhome said:

Hello everyone, I have owned a 961 Commando from new in 2016. When i received it it sounded like a guy hammering an anvil. So bad that I returned it to Norton who said they did some 'adjustments' but nothing worked so....... after a lot of head scratching and using my engineering knowledge and some work carried out by a couple of machine shops near , I engineered a remedy. I've decided to share that remedy after riding it for some miles.
Firstly I will explain why the primary gear literally 'hammers'., if it hasn't already been posted (please bear with me if it has). Simply the intermediate split anti-backlash gear can never work between two gears. This is a fact and can be confirmed by any reputable gear manufacturer. Anti-backlash gears can only work in one direction. So what did I do ? I managed to blag some spare gears (primary and intermediate anti-backlash) from a guy who held a lot of sympathy in Norton back in 2015/16. This gave me the opportunity to think and try solutions. Although the gear drive train will, never be super quiet (unlike my Triumph Bonneville America) my 961 is significantly quieter.
I have just stripped out the primary gear drive train to check all is okay and taken the opportunity to take photos . If any one is interested in what I have done then click on my thread and I continue this thread with what I tried...what failed and what worked over the next week or so.. with photos etc.

Click to expand...

Hello and welcome . Can I ask why the triumph is so quiet? Is it bevel cut gears ? My Indian is gear drive primary and it is also quiet. Maybe I mean helical cut ?

TonyA said:

Hello and welcome . Can I ask why the triumph is so quiet? Is it bevel cut gears ? My Indian is gear drive primary and it is also quiet. Maybe I mean helical cut ?

Click to expand...

stevejhome said:

Hello everyone, I have owned a 961 Commando from new in 2016. When i received it it sounded like a guy hammering an anvil. So bad that I returned it to Norton who said they did some 'adjustments' but nothing worked so....... after a lot of head scratching and using my engineering knowledge and some work carried out by a couple of machine shops near , I engineered a remedy. I've decided to share that remedy after riding it for some miles.
Firstly I will explain why the primary gear literally 'hammers'., if it hasn't already been posted (please bear with me if it has). Simply the intermediate split anti-backlash gear can never work between two gears. This is a fact and can be confirmed by any reputable gear manufacturer. Anti-backlash gears can only work in one direction. So what did I do ? I managed to blag some spare gears (primary and intermediate anti-backlash) from a guy who held a lot of sympathy in Norton back in 2015/16. This gave me the opportunity to think and try solutions. Although the gear drive train will, never be super quiet (unlike my Triumph Bonneville America) my 961 is significantly quieter.
I have just stripped out the primary gear drive train to check all is okay and taken the opportunity to take photos . If any one is interested in what I have done then click on my thread and I continue this thread with what I tried...what failed and what worked over the next week or so.. with photos etc.

Click to expand...

Hi , sounds very interesting , would be great to see what you’ve done to improve the situation….

TonyA said:

Hello and welcome . Can I ask why the triumph is so quiet? Is it bevel cut gears ? My Indian is gear drive primary and it is also quiet. Maybe I mean helical cut ?

Click to expand...

Not sure why there is such a difference, but I suspect its just tighter engineering tolerances and balancer shaft(s) design/configuration

Okay, thanks for everyone's interest. I will get straight to the job. All of my description will be refer to photos in the Dropbox link at the end , any questions just ask! All of the work shown was done by a couple of machine tool workshops (they have high tech and basic precision machine shop equipment) . As I stated earlier an anti-backlash gear cannot work between two gears..so everything was orientated around that engineering fact.
So First attempt of solution: I had a spare primary drive gear machined narrower so that the gear then missed the narrow gear section of the anti-backlash gear. Photo c. Tried it with backlash 'C' spring tensioned in both directions. Result was still a lot of noise.
Second attempt of solution: Reinstalled original unmodified primary drive gear, then had the clutch basket drive gear machined narrower so that it missed the narrow gear section of the anti-backlash gear. Photo d and hh. Tried it with backlash 'C' spring tensioned in one direction then the other. Result was noticeable reduction in clatter but not enough improvement.
So I scratched my head and tried again.

Third attempt of solution: Kept the modified clutch basket drive gear and had 'C' spring the recess in the anti-backlash gear machined deeper to accommodate two anti-backlash 'C springs' Photo s and x. Extended the stop pins Photo y to engage with the depth of two springs. Result ! Huge reduction in clatter. (As a point of note.... I have not shown photos of the modified recess in the anti-backlash because I had tested a couple of tensions so didnt want to disturb it....but you get the idea. The anti-backlash tension was also achieved with a lot less rotation between the narrow gear and backlash gear but still achieved an increase in spring rate i.e. more tension)

I also noticed the clutch basket dampening springs were loose in their recesses so i I tig welded metal spacer plates to remove looseness photo k . h .

Finally I also changed gearbox oil to a different SAE. FUCHS Silkolene Gear Oil Light SAE 75, SAE80. This made the gears shift nicely in my opinion.

Its been an interesting journey but I'm happy with the results. More importantly the gears were showing signs of galling against the narrow back-lash part of the gear. Since the mods there is no further degradation. As you can see i had the transmission apart on probably eight occasions so it was not plain sailing, however I was really luck that the two companies that had the precision engineering workshops happened to be owned by fellow bikers ! so they did all of the machining without cost ! Real gents ! Link to drop box is https://www.dropbox.com/scl/fo/1y9k...ey=py3owpc3s5d8xdq2kg35iaxpm&st=on9h53ug&dl=0

Thanks for this Steve, very impressive amount of trial an error work you’ve done. So in the final (successful) incarnation, the backlash gear is only acting on the crankshaft gear, is that correct?

cliffa said:

Thanks for this Steve, very impressive amount of trial an error work you’ve done. So in the final (successful) incarnation, the backlash gear is only acting on the crankshaft gear, is that correct?

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Yes that's right......the majority of clack Is between the primary and intermediate gear which also drives the balancer shaft