Why does the 961 vibrate so much ?

Fast Eddie said:

And if I do ride it… and don’t like it… I’ll pro’lly jus’ keep quiet cuz I’ve seen how y’all beat up thoze guyz !

Click to expand...

scaredy cat !

An interesting post from a new joiner to the Facebook group…

”Hi! I'm new to this group. I recently joined because yesterday I put down a deposit on a 961 SP at Crazy Horse following a couple of test rides with the Norton events team on Thursday. I rodé 2 961's , the first had only done 400 miles and the second had done 2.7k miles. I was very pleasantly surprised at how much better the ride was on the higher mileage bike”

And went on to say…

”the first bike vibrated so much that my hands went numb and it felt like the engine internals were trying to come through the seat. The second bike with 2.7k was enjoyable to ride with pleasurable levels of vibration. I would not have purchased on the strength of the first ride. ”

Fast Eddie said:

If you mean production tolerances between identical engines, then I do not believe that CR differences would be sufficient to cause noticeable differences in engine vibration.

Click to expand...

I think it’s the primary gears there straight cut but I am sure they could get them better by better tolerances

I have’nt heard many other 961’s in the flesh but mine appears to be quite quiet, mechanical noise certainly not excessive for an air cooled bike - the short open pipes help of course.

I used to get a numb throttle hand regularly, depending how aggressively I was riding and where within the rev range, for the first few years of ownership. Can’t remember exactly when that settled, but I get no hint of it now.

True to say also I suppose, that clatter may not necessarily lead to excessive vibration.

Joe 961 said:

I think it’s the primary gears there straight cut but I am sure they could get them better by better tolerances

Click to expand...

Good point and thats another reason for the noise as well as the vibration that some experience..

The gentle whirring and mild chattering of NORMAL straight cut gears is NOT the clattering and banging that worries people I can assure you.

Folks would greet me as I pulled up saying ‘sounds like your big ends gone mate’ !

Unless the play was massively too big, and then the uneven forces created by the 270 crank and balance shaft acting on these sloppy gears, that I could imagine being part of the issue?

I honestly don’t know what causes it. But I do know the noise mine made was not ok from the perspective of a mechanically sympathetic mind.

Mine is quiet

nopdog said:

Mine is quiet

Click to expand...

Well you’re just showing off … !

Fast Eddie said:

Well you’re just showing off … !

Click to expand...

And I guess it’s just luck of the draw

nopdog said:

Mine is quiet

Click to expand...

Banana skins and cheese cloth !

Fast Eddie said:

The gentle whirring and mild chattering of NORMAL straight cut gears is NOT the clattering and banging that worries people I can assure you.

Folks would greet me as I pulled up saying ‘sounds like your big ends gone mate’ !

Click to expand...

Indeed!
If you own a Jap sportbike, and I've owned many, with the stock-super quiet exhaust system, you can hear the primary gear whine when revving the engine. They also use spur (straight cut) gear drive in their primaries. Nothing untoward about that sound.
The grinding, or slapping noises that some 961 engines produce are another matter entirely. They would seem to indicate that something is not quite right in the motor. I have never seen any gear driven primary with an intermediate gear other than the 961's. That is where I would focus the attention of my engineering staff. If I intending to keep producing the 961 into the future, I would re-design the crankcases, and drive the balancer shaft off of the timing side, and eliminate the intermediate primary gear all together.

BritTwit said:

Indeed!
If you own a Jap sportbike, and I've owned many, with the stock-super quiet exhaust system, you can hear the primary gear whine when revving the engine. They also use spur (straight cut) gear drive in their primaries. Nothing untoward about that sound.
The grinding, or slapping noises that some 961 engines produce are another matter entirely. They would seem to indicate that something is not quite right in the motor. I have never seen any gear driven primary with an intermediate gear other than the 961's. That is where I would focus the attention of my engineering staff. If I intending to keep producing the 961 into the future, I would re-design the crankcases, and drive the balancer shaft off of the timing side, and eliminate the intermediate primary gear all together.

Click to expand...

Yes and we were told on here somewhere that both Ollie and TVS were investigating improvements….

TonyA said:

I like this thinking and for a truly dedicated owner with resources made be our only solution .

Click to expand...

Hello Again , I have done some things to my Norton 961 that have improved the the level of felt vibration . I would like to put all of these things in one place .
Exhaust Mounting at the muffler hangers and at the H pipe below never to be tight and system must be aligned so no bending , flex or stress on it . The hangar bolts must slide through freely. Use all metal lock nuts never nyloc because of heat . My bike came with all metal lock nuts from OEM . The system should be able to expand and contract as it heats up.



Footpegs for me were the worst offender. I have solved this with different footpegs which mount with minor modification .

Next are the handgrips , Progrip 717 work verywell with color selections too . If you need more anti-vibe you can layer on foam grip sleeves but I find this too big for optimal road work . And bar end mirrors act as bar end weights .


And lastly there is gearing if you need less RPM at high speed . You can go all the way down to 47T and no need to alter chain length. I have run a 47T but my advice is to try the 48T if you go this route . I am currently running stock 18T/50T and am very happy with it. I Have good pick up and can run 80 TO 85 all day with ease and comfort .

TonyA said:

Hello Again , I have done some things to my Norton 961 that have improved the the level of felt vibration . I would like to put all of these things in one place .
Exhaust Mounting at the muffler hangers and at the H pipe below never to be tight and system must be aligned so no bending , flex or stress on it . The hangar bolts must slide through freely. Use all metal lock nuts never nyloc because of heat . My bike came with all metal lock nuts from OEM . The system should be able to expand and contract as it heats up.

Footpegs for me were the worst offender. I have solved this with different footpegs which mount with minor modification .

Next are the handgrips , Progrip 717 work verywell with color selections too . If you need more anti-vibe you can layer on foam grip sleeves but I find this too big for optimal road work . And bar end mirrors act as bar end weights .

And lastly there is gearing if you need less RPM at high speed . You can go all the way down to 47T and no need to alter chain length. I have run a 47T but my advice is to try the 48T if you go this route . I am currently running stock 18T/50T and am very happy with it. I Have good pick up and can run 80 TO 85 all day with ease and comfort .

Click to expand...

Almost forgot my unfair advantage ; my seat :

TonyA said:

Almost forgot my unfair advantage ; my seat :

Click to expand...

I'm trying something similar Tony, although I haven't ridden it like this yet. I've fitted a longer M10 bolt on the centre hanger which has a compression spring over it. It allows the centre section to slide backwards and forwards slightly. I have also reversed the rubber bushes and spacer in the silencer mount on the subframes, as the trianglular brackets seemed to be contacting the metal of the frame. I'll test it over the next few days if the weather holds.

I suspect your running the 961 at higher revs that the Harley, which must make a difference.

Bevelheadmhr said:

I suspect your running the 961 at higher revs that the Harley, which must make a difference.

Click to expand...

But that doesn’t explain why the 961 vibrates more than the Harley below 5,500rpm does it ?

My original question behind this thread still stands.

I have a 1007cc Seeley Commando track bike. BIG engine, high CR, rigid mounted in a lightweight frame with a 360 crank and no balance shaft.

I do not believe it vibrates any worse than my 961 did !

With a 270 crank AND a balance shaft, the 961 shouldn’t vibrate any more than a 1200 Hinckley Bonnie.

I honestly don’t understand …

Vibration on these is massively subjective....far too many variables ie what bike are they comparing against and more importantly, what riding gear are they wearing? My Domi is probably one of the most extreme 961s out there, and I've learnt that even the socks I wear (Goldtop, cheers Richard for introducing me to them) make a difference, let alone boots, gloves etc

cliffa said:

I'm trying something similar Tony, although I haven't ridden it like this yet. I've fitted a longer M10 bolt on the centre hanger which has a compression spring over it. It allows the centre section to slide backwards and forwards slightly. I have also reversed the rubber bushes and spacer in the silencer mount on the subframes, as the trianglular brackets seemed to be contacting the metal of the frame. I'll test it over the next few days if the weather holds.View attachment 116523View attachment 116524

Click to expand...

Hi Cliffa , I think you are on the right track. I can say mine is pretty darn good now and I can ride fast and far on it. I see you are running the late model Donington de-cat pipe !

Virtually no vibes present in the bars or pegs on mine. That was not always the case - It was there originally, mainly through the bars (sufficient to numb the fingers on each ride from memory).

Time/mileage, failure of the exhaust lower mount and the fitting of weighted Rizoma bar end mirrors have led to this outcome I believe. No idea which of these had most impact, but I suspect it was the removal of that centre underslung exhaust mount.