Why does the 961 vibrate so much ?

TonyA said:
I like this thinking and for a truly dedicated owner with resources made be our only solution .
Click to expand...
What is the bore to stroke of the 961? I don’t recall.

Tony do you know the rod length or piston compression height? I’m curious.
 
Remember the Bushman thread where he tore down his motor and found the synchronization between the crank and the balancer to be off by 1/2 a gear tooth. I believe misplacement of the key for either the driving gear on crank or the balancer shaft gear will be a problem at 4,000 RPM. Wouldn't matter if the balancer were designed correctly or not, if it's not synchronized properly with the crank there will be vibes.
Did Norton actually do QC on parts arriving from suppliers, or cross their fingers, and just bolt them up?
 
BritTwit said:
Remember the Bushman thread where he tore down his motor and found the synchronization between the crank and the balancer to be off by 1/2 a gear tooth. I believe misplacement of the key for either the driving gear on crank or the balancer shaft gear will be a problem at 4,000 RPM. Wouldn't matter if the balancer were designed correctly or not, if it's not synchronized properly with the crank there will be vibes.
Did Norton actually do QC on parts arriving from suppliers, or cross their fingers, and just bolt them up?
Click to expand...
Yes I remember that thread, but I had assumed TVS would have corrected any such faults, which may, or may not, be the case, and the reviews of new bikes got me wondrin…
 
When you balance a 360 degree crank for racing, it is only ever about primary balance. The crank in my 850 motor is balanced at about 72%. It runs extremely smooth in the rev range I use which is betweern 5,500 RPM and 7000 RPM. At low revs the crank is capable of rocking the bike backwards and forwards. Phil Irving stated that a 270 degree crank should be the smoothest. However he probably was not thinking about secondary vibration. With a 270 degree crank, it is probable that end for end rocking occurs at high revs. The angle on the cylinders of Ducatis and Vincents give a similar effect to a 270 crank in a vertical twin But in those two motors, the crank assembly is narrow. So secondary balance is not a factor for concern.
With a race bike big pulses at low revs make the bike feel good, but you would not want that with a road bike. I love the way my Seeley 850 feels at all revs. 'Some things are so bad that they are good' ? When you ride out the pit gate, it is always thumping and when it spins-up the thump disappears - it gives a great adrenalin rush. It is the reason I never start my bike at home - I lnow what that noise means and I always have a uncontrollable urge to ride the bike. There are cops living near me.
 
Fast Eddie said:
Yes I remember that thread, but I had assumed TVS would have corrected any such faults, which may, or may not, be the case, and the reviews of new bikes got me wondrin…
Click to expand...
I can't image the TVS/Norton folks not focusing in on that known issue. If it remains on the new 961s it may say a lot about the thoroughness of that re-engineering effort.
I hope I'm wrong.
 
Fast Eddie said:
Let me start by saying that personally, I didn’t find that mine vibrated that badly, in fact it was part of the charm for me.

But nevertheless, they do vibrate, it’s something that all reviewers comment on, some quite negatively.

Why is this?

Some context to my pondering:

I had an 1800cc Harley Dyna, which means it had a rubber mounted engine with no balance shafts (like an old Commando), although it shook a bit at idle, it didn’t vibrate badly in use at all. I’ve replaced it with an 1800cc softail. This has the engine solidly mounted, but it has balance shafts (like a modern Commando). The solidly mounted balance shaft engine is much SMOOTHER than the rubber mounted one, in fact it is really very smooth (rather than just smooth for a Harley) in use.

So, balance shafts DO WORK.

Meanwhile, the 961 has a balance shaft AND a 270 crank layout, this is well known to be the smoothest configuration for a parallel twin, effectively making it a 90 degree eve twin.

So, the 961 has the smoothest possible crank configuration AND it has a balance shaft.

So… why does it still vibrate so much ??
Click to expand...
Perhaps some kind of rubber engine mounts could be developed to isolate the rider from the vibrating bits and then....oh wait......
 
Tornado said:
Perhaps some kind of rubber engine mounts could be developed to isolate the rider from the vibrating bits and then....oh wait......
Click to expand...
That seems like a band aid, no?
Just do the proper QC on the production components to make sure they are correctly sync-ed, if not, they get sent back to the supplier for correction. Maybe hire a vibration engineer, and buy the machinery to do the sync-ing in-house.
Result - smoother engine, and end of problem, forever.:)
 
BritTwit said:
Remember the Bushman thread where he tore down his motor and found the synchronization between the crank and the balancer to be off by 1/2 a gear tooth. I believe misplacement of the key for either the driving gear on crank or the balancer shaft gear will be a problem at 4,000 RPM. Wouldn't matter if the balancer were designed correctly or not, if it's not synchronized properly with the crank there will be vibes.
Did Norton actually do QC on parts arriving from suppliers, or cross their fingers, and just bolt them up?
Click to expand...
Based on TVS Norton's advertisment alone , I would have thought they would have all of this checked and double checked.
 
TonyA said:
Based on TVS Norton's advertisment alone , I would have thought they would have all of this checked and double checked.
Click to expand...
Me too.
And also have spent enough time in-house test riding the new unit to make sure the vibes and noises are minimized to the greatest extent possible.
 
We have a 2022 Commando Classic, and the vibrations are something that are an integral part of the nature of the bike. I can say it makes it feel just that right kind of special. It would be a sad moment to not have them, actually. Saying that, the intensity is just right. On our bike, the rev range goes through several consecutive stages of on-off-on vibrations which stop at or around 4500 rpm. Beyond that it just smoothly roars.
I briefly test rode a Donington MkII CR and it vibrated so much that my feet and hands were going numb. Reportedly, this bike suffered from a bad injector, but I can´t say if it was the cause or not.
On our bike, the vibrations may have calmed down during break-in, or I may have gotten used to them, or it´s a combination of both. The most numbing I get is in my right-hand index finger which I have on the brake lever at all times. Every once in a while, I have to take my right hand off the throttle and shake it out. The last ride out was 370 km, or 8 hours on twisty roads, which was a lot, and I must´ve done that ten times, but this can also be attributed to body posture, body size, weight, gear, etc. To put in in perspective, I definitely feel it, but when I run our two-stroke weed cutter for three or four hours, I feel the wear and numbing about twice as much.
 
CR961 said:
We have a 2022 Commando Classic, and the vibrations are something that are an integral part of the nature of the bike. I can say it makes it feel just that right kind of special. It would be a sad moment to not have them, actually. Saying that, the intensity is just right. On our bike, the rev range goes through several consecutive stages of on-off-on vibrations which stop at or around 4500 rpm. Beyond that it just smoothly roars.
I briefly test rode a Donington MkII CR and it vibrated so much that my feet and hands were going numb. Reportedly, this bike suffered from a bad injector, but I can´t say if it was the cause or not.
On our bike, the vibrations may have calmed down during break-in, or I may have gotten used to them, or it´s a combination of both. The most numbing I get is in my right-hand index finger which I have on the brake lever at all times. Every once in a while, I have to take my right hand off the throttle and shake it out. The last ride out was 370 km, or 8 hours on twisty roads, which was a lot, and I must´ve done that ten times, but this can also be attributed to body posture, body size, weight, gear, etc. To put in in perspective, I definitely feel it, but when I run our two-stroke weed cutter for three or four hours, I feel the wear and numbing about twice as much.
Click to expand...
Put it down to your gloves are too tight,
Same thing happens to me!
 
I wanted to add another issue on this level. There have also been issues with the main bearings.
 
CR961 said:
We have a 2022 Commando Classic, and the vibrations are something that are an integral part of the nature of the bike. I can say it makes it feel just that right kind of special. It would be a sad moment to not have them, actually. Saying that, the intensity is just right. On our bike, the rev range goes through several consecutive stages of on-off-on vibrations which stop at or around 4500 rpm. Beyond that it just smoothly roars.
Click to expand...
I am glad you like your bike. I would love to drive a Birmingham Norton 961 and see for myself.
 
I can’t believe anyone here would actually think that TVS would really spend the time and R&D going over the 961.
Their main concerns were telling everyone of the multiple millions they’ve spent building the new factory.
Not the hundreds of thousands of dollars to go over the 961.
R&D cost money.
Building a factory cost money.
Fixing mistakes from suppliers and from the previous owners cost money.

The 961 sold before, and it’s selling now.
The Good. The bad. And the ugly.
It’s selling enough to make a small profit, more than if they wasted money in improvements.

Why do you think they refuse to tell off of the 300 parts they changed or addressed.
How many fuses and relays on a 961?
How many bolts?
How many gaskets?
Etc etc
 
Voodooo said:
I can’t believe anyone here would actually think that TVS would really spend the time and R&D going over the 961.
Their main concerns were telling everyone of the multiple millions they’ve spent building the new factory.
Not the hundreds of thousands of dollars to go over the 961.
R&D cost money.
Building a factory cost money.
Fixing mistakes from suppliers and from the previous owners cost money.

The 961 sold before, and it’s selling now.
The Good. The bad. And the ugly.
It’s selling enough to make a small profit, more than if they wasted money in improvements.

Why do you think they refuse to tell off of the 300 parts they changed or addressed.
How many fuses and relays on a 961?
How many bolts?
How many gaskets?
Etc etc
Click to expand...
I see what you're saying and I think if they had full disclosure about the improvements this would help sales for them . I also have to add that there have been some improvements based on the new cam chain adjuster blocks I bought.
 
You must log in or register to reply here.

Similar threads

baz
Crank balance factor
2 3 4 5 6 7
Replies
128
Views
3,497
acotrel
acotrel
Britstuff
How much lateral rear suspension movement is acceptable?
2
Replies
30
Views
848
ilikevelos
I
B
Reactions of other riders to your 961?
Replies
6
Views
208
City Garage
City Garage
M
This may interest Norton owners as I have seen the use of decompressor buttons on high comp Norton engines.
Replies
10
Views
427
o0norton0o
o0norton0o
Fast Eddie
JS lightweight pistons and rods
Replies
13
Views
842
Hortons Norton
Hortons Norton
Back
Top