Current production Norton 961 Parts

I think just removing the casting slag from the port, and putting a swirl finish on inside port surface would help overall flow.
No need to remove any significant material, or reshape the ports though.
If the owner intends to use the same airbox, and throttle bodies - HP increase will be minimal.
Now add an increase to the airbox plenum by 50%, that would probably get some nice results.
No one really has any experience with hi-performance cams on these bikes, so that would be shot in the dark.

A supercharger, now that's the ticket.:p
 
BritTwit said:
I think just removing the casting slag from the port, and putting a swirl finish on inside port surface would help overall flow.
No need to remove any significant material, or reshape the ports though.
If the owner intends to use the same airbox, and throttle bodies - HP increase will be minimal.
Now add an increase to the airbox plenum by 50%, that would probably get some nice results.
No one really has any experience with hi-performance cams on these bikes, so that would be shot in the dark.

A supercharger, now that's the ticket.:p
Click to expand...
Delete the air box and add velocity stacks.
 
My suggestion would be to try and get Jim Comstock interested:


He‘s done extensive head flow testing on ‘old’ Commandos. His package of head work gave a 9rwhp increase on mine. That’s a LOT.

Check out this thread from the classic forum:

www.accessnorton.com

Head flow testing.

I would like to build up a database of flowtests on modified Norton heads. The tests would be done on one intake port and be from 0 to .450 lift and would include a single velocity measurement measured central in the port 3/4 inch in front of the guide. If anyone has a modified head setting...
www.accessnorton.com www.accessnorton.com

BTW the classic forum is a bit different to this one, most conversations are about improvement modifications rather than fixing problems ;)
 
Fast Eddie said:
My suggestion would be to try and get Jim Comstock interested:


He‘s done extensive head flow testing on ‘old’ Commandos. His package of head work gave a 9rwhp increase on mine. That’s a LOT.

Check out this thread from the classic forum:

www.accessnorton.com

Head flow testing.

I would like to build up a database of flowtests on modified Norton heads. The tests would be done on one intake port and be from 0 to .450 lift and would include a single velocity measurement measured central in the port 3/4 inch in front of the guide. If anyone has a modified head setting...
www.accessnorton.com www.accessnorton.com

BTW the classic forum is a bit different to this one, most conversations are about improvement modifications rather than fixing problems ;)
Click to expand...
It would have been great if the vintage commando guys would have taken the same interest in the Norton 961 . It appears that lots of improvements have been made in this 961 just for them ! Larger valves and ports , 961cc with 79mm stroke , center crankshaft bearing support , center camshaft bearing support , roller lifters , roller rockers , 5 speed transmission etc.. Intake Valve 44.5mm , intake port 36mm at throttle body mating surface , tapering to 34mm around 15 mm down the port. Effiecient combustion chamber (relatively) . The biggest problem I see is the bikes were expensive and not plentiful . Therefore none have made it into the tuners hands .
 
The 961 definitely has qualitative improvements, just not developed as you said.
I think the head has a pretty good general design.
Even the combustion chamber shape is quite good for a 2 valve head.
Jim Schmidt on the Classic forum is working on 750 heads to create the same Harley XLR750 type 'bathbub' combustion chamber as the 961's.
Seems to be the way to go to extract power and torque.
 
TonyA said:
It would have been great if the vintage commando guys would have taken the same interest in the Norton 961 . It appears that lots of improvements have been made in this 961 just for them ! Larger valves and ports , 961cc with 79mm stroke , center crankshaft bearing support , center camshaft bearing support , roller lifters , roller rockers , 5 speed transmission etc.. Intake Valve 44.5mm , intake port 36mm at throttle body mating surface , tapering to 34mm around 15 mm down the port. Effiecient combustion chamber (relatively) . The biggest problem I see is the bikes were expensive and not plentiful . Therefore none have made it into the tuners hands .
Click to expand...
That’s all true Tony. That’s why I liked the idea so much. To my eye the 961 is not a modern retro as such, it’s a genuine development of the older bike.

I think the classic tuners kept away for a number of reasons....

First and foremost being that it is an entirely different machine. It doesn‘t fit with their knowledge, skill sets or even equipment.

Also, some simply have no interest, they like the old ones, period!

Most are also busy enough doing what they do.

As you say, the bikes are limited, so their market would be limited. So it’s a lot to go through to access a tiny market.

And finally, most of those that did venture into the foray were stamped all over by Norton !!
 
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TonyA said:
It would have been great if the vintage commando guys would have taken the same interest in the Norton 961 . It appears that lots of improvements have been made in this 961 just for them ! Larger valves and ports , 961cc with 79mm stroke , center crankshaft bearing support , center camshaft bearing support , roller lifters , roller rockers , 5 speed transmission etc.. Intake Valve 44.5mm , intake port 36mm at throttle body mating surface , tapering to 34mm around 15 mm down the port. Effiecient combustion chamber (relatively) . The biggest problem I see is the bikes were expensive and not plentiful . Therefore none have made it into the tuners hands .
Click to expand...
Until a good engine builder get his hands on a engine, you’ll never see aftermarket performance parts. There is no reason why a 961 can not have better cams, head / head work, valves, pistons etc.
If Harley has a 114 and 117 ci Milwaukee 8 and a 131 kit for the Milwaukee 8, there is no reason why a 961 can’t have performance parts as well.

Tony you already have a spare head. I would be willing to pitch in some $$ for testing and development. It would be interesting to see what gains could be made with head work, cam and some dyno tuning.

Does anyone know the head gasket thickness and the piston to valve clearance? A bump in compression would also help
 
Last edited by a moderator:
Fast Eddie said:
My suggestion would be to try and get Jim Comstock interested:


He‘s done extensive head flow testing on ‘old’ Commandos. His package of head work gave a 9rwhp increase on mine. That’s a LOT.

Check out this thread from the classic forum:

www.accessnorton.com

Head flow testing.

I would like to build up a database of flowtests on modified Norton heads. The tests would be done on one intake port and be from 0 to .450 lift and would include a single velocity measurement measured central in the port 3/4 inch in front of the guide. If anyone has a modified head setting...
www.accessnorton.com www.accessnorton.com

BTW the classic forum is a bit different to this one, most conversations are about improvement modifications rather than fixing problems ;)
Click to expand...
I emailed James to see if he’s interested in a 961.
 
Voodooo said:
Until a good engine builder get his hands on a engine, you’ll never see aftermarket performance parts. There is no reason why a 961 can not have better cams, head / head work, valves, pistons etc.
If Harley has a 114 and 117 ci Milwaukee 8 and a 131 kit for the Milwaukee 8, there is no reason why a 961 can’t have performance parts as well.

Tony you already have a spare head. I would be willing to pitch in some $$ for testing and development. It would be interesting to see what gains could be made with head work, cam and some dyno tuning.

Does anyone know the head gasket thickness and the piston to valve clearance? A bump in compression would also help
Click to expand...
WOW ! I never expected this much interest . I have a new head gasket , the piston to valve clearance I don't know.
 
TonyA said:
WOW ! I never expected this much interest . I have a new head gasket , the piston to valve clearance I don't know.
Click to expand...
If TVS-Norton do supply 961 spare parts going forward, that would make 961 performance tuning a bit more realistic.
If you break something, you'll be able to buy replacement parts.
Pricey parts no doubt, but available.
 
TonyA said:
WOW ! I never expected this much interest . I have a new head gasket , the piston to valve clearance I don't know.
Click to expand...
Are you willing to share the cost of the head you purchase here publicly or in a pm? Are you able to mic the thickness of the head gasket?
im interested in the combustion chamber cc along with the intake and exhaust port cc and Cfm Flow rates.

there’s no reason why a 961 couldn’t make over 100 hp.
 
Last edited by a moderator:
There was (possibly still is?) one being raced in NZ. As i understand it, it went through a serious performance shop and was up to 110hp, i don't know any details of what was done.
The one time i have seen it racing was on a street circuit and he was dicing with an air cooled Duc 900.
I did hear that he lunched the engine at one stage when the balance shaft let go.
 
Voodooo said:
Are you willing to share the cost of the head you purchase here publicly or in a pm? Are you able to mic the thickness of the head gasket?
im interested in the combustion chamber cc along with the intake and exhaust port cc and Cfm Flow rates.

there’s no reason why a 961 couldn’t make over 100 hp.
Click to expand...
I like your enthusiasm , the cost of the head was between 600 and 700 pounds , closer to 700 if I remember correctly. Without putting the valves in and using measured volume of water I wouldn't know how to do that . If you are currently working with a speed shop , it may be best to use them.
 
Yeah, there was a forum member who had a balancer shaft snap.
I think there was also a member have a camshaft break too.
But we don't hear these issues very often, knock on wood.

I remember the NZ guy report, he had quite a bit of work done to his 961.
 
The reason I bought the head was to replace mine if the valve guides get worn out like David C's did. David managed to get replacement guides somehow though so I would only be down for shorter while in that case. I don't like being down especially with this bike.
 
BritTwit said:
Yeah, there was a forum member who had a balancer shaft snap.
I think there was also a member have a camshaft break too.
But we don't hear these issues very often, knock on wood.

I remember the NZ guy report, he had quite a bit of work done to his 961.
Click to expand...
I don't remember the camshaft break. I do remember the lobe wear issue on Richard-7 . The balance shaft breaking was Raphi , there may be others I have not heard of. David C said that the bearing fails first then takes out the balance shaft . It is paramount in a high performance engine that these bearings are replaced with heavy duty bearings. Brass cage FAGs was what David got for mine .
 
The camshaft break was Raphi too.
I would also have the balancer shaft magnafluxed to check for cracks before putting it back in.
Maybe have it Tufftrited too.
 

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