Inlet upgrade?

A

Al's#5

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Feb 4, 2020
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Years ago an upgrade I carried out on a Rocket 3 was from 28 to 30mm carbs and the improvement was great, might of helped that I tapered the adaptors for them but I digress. Now the 961 has 38mm throttle bodies, are 40mm worth thinking about? Surely there's an formula for this but just thinking 1200 Sportster 40mm, 865 Triumph 36, so the 961 sits nicely at 38. Now the dilemma, 600 single with a 45mm throttle body that I can't fault and a mate once put twin 40 Webers on a 1000 Kwacka, a bit rough low down but flying topend, and the sound was great. Any suggestions appreciated.
 
Al's#5 said:
Years ago an upgrade I carried out on a Rocket 3 was from 28 to 30mm carbs and the improvement was great, might of helped that I tapered the adaptors for them but I digress. Now the 961 has 38mm throttle bodies, are 40mm worth thinking about? Surely there's an formula for this but just thinking 1200 Sportster 40mm, 865 Triumph 36, so the 961 sits nicely at 38. Now the dilemma, 600 single with a 45mm throttle body that I can't fault and a mate once put twin 40 Webers on a 1000 Kwacka, a bit rough low down but flying topend, and the sound was great. Any suggestions appreciated.
Click to expand...

This is a great idea that you should pursue.
On the Triumph Air-Cooled Twin forum there was a member who took the throttle bodies off a street triple and used them on a EFI Bonneville 900 twin. Results were tremendous. The stock throttle bodies were 36mm the street triple were 43mm. The Bonnie also got a big valve head, and a 903 big bore job. The air box was removed and foam air filters installed. Also, since the street triple throttle body assemble has three throttle bodies, he had to disassemble the whole assemble, trim down the linkage to use just two throttle bodies that were spaced properly for the Bonnie's distance between inlet centers. Port matching inlet manifolds will be required as well.

Stock Bonnie 900 power is about 65HP at the crank - around 55 RWHP
The reworked 903 produced nearly 85 RWHP on a dyno.
It did require quit a bit of dyno tuning to get all the pieces to work together properly.

The 961's air box will be the first impediment to extracting additional power from the engine.
If you want to do the throttle body swap, you'll have to bin the airbox too.
 
I do wonder what hitherto well hidden foibles would be unmasked if the 961 was tuned for more oomph...?
 
Dunno, but if you're only going after throttle bodies and airboxes then you're only looking at maybe a 10HP increase.
I don't think that would be much cause for alarm.
But point taken.
Clutches have seen issues as well as balancer shafts, even rockers.

I think the the major components are pretty bullet proof.
Crank, rods, pistons, tranny.....

Sure would be interesting for someone to offer up their 961 as a guinea pig test unit.
 
Al's#5 said:
I was thinking to stay with the efi but a pair of flatslides would be nice.
Click to expand...
I am a carb guy so I would find this wonderful too.
However, adapting new throttle bodies, and retaining the stock EFI would be much simpler.

Don't forget the EFI system not only supplies the fuel pulse to the injectors, it also controls the ignition timing.
If you mount carbs, and bypass the electronic fuel control, how will the ignition pulse be controlled?
Carbs will dump a whole lot of fuel into the system, with a whole lot more ending up in the exhaust.
That will make the O2 sensors cause the ECU to screw with the ignition pulses trying to adjust combustion.
Also, the temp sensor data will force the ECU to make ignition changes as well,
This will not be optimal for a carb-ed engine.

The best outcome for a carb-ed engine would be to fit a separate ignition module, preferably one that allows tuning. Like the igniter box used on the Hinckley carb-ed Triumph Bonneville line prior to 2016. The igniter uses a transducer and timing ring, like the 961 has, and should be adaptable to the 961. The igniter box also has inputs for TPS, sidestand switch, clutch switch, and kill switch. The box has output signals for ignition coils, and tach signal.

So:

1. Fit new throttle bodies, and remove airbox and fit foam air filters. dyno tune the motor, done.
2. Fit new carbs and either:
a. Screw with the EFI system to get the ignition to work properly with the new fuel flow from the carbs, and the sensor data it produces.
or
b. Bypass the ECU ignition completely and install a different ignition module, and get it all to work together.
 
BritTwit said:
I am a carb guy so I would find this wonderful too.
However, adapting new throttle bodies, and retaining the stock EFI would be much simpler.

Don't forget the EFI system not only supplies the fuel pulse to the injectors, it also controls the ignition timing.
If you mount carbs, and bypass the electronic fuel control, how will the ignition pulse be controlled?
Carbs will dump a whole lot of fuel into the system, with a whole lot more ending up in the exhaust.
That will make the O2 sensors cause the ECU to screw with the ignition pulses trying to adjust combustion.
Also, the temp sensor data will force the ECU to make ignition changes as well,
This will not be optimal for a carb-ed engine.

The best outcome for a carb-ed engine would be to fit a separate ignition module, preferably one that allows tuning. Like the igniter box used on the Hinckley carb-ed Triumph Bonneville line prior to 2016. The igniter uses a transducer and timing ring, like the 961 has, and should be adaptable to the 961. The igniter box also has inputs for TPS, sidestand switch, clutch switch, and kill switch. The box has output signals for ignition coils, and tach signal.

So:

1. Fit new throttle bodies, and remove airbox and fit foam air filters. dyno tune the motor, done.
2. Fit new carbs and either:
a. Screw with the EFI system to get the ignition to work properly with the new fuel flow from the carbs, and the sensor data it produces.
or
b. Bypass the ECU ignition completely and install a different ignition module, and get it all to work together.
Click to expand...
Be interesting to see what TVS do with the last batch of 961s.
They can’t leave the door with the same recognised faults ,Can they!!
 
MAK said:
They can’t leave the door with the same recognised faults ,Can they!!
Click to expand...

I don't think so.
After all, these last 961's are "new" product for the new Norton company, even if they represent the end of the line for the 961.
TVS-Norton will have to support these final units, like any other product that they push out the door.
There may have already been fixes in the pipeline for many of the 961's foibles when the plug was pulled on SG.
Maybe these fixes were never introduced by SG because they would have cost too much.
I think there will be some improvements on these final 961s, just nothing really significant.
That would involve a greater investment in development than I think TVS wants to make in a discontinued model.

Finishing off these last few units for customers is TVS's want of building that well of positive customer opinion.
 
BritTwit said:
I don't think so.
After all, these last 961's are "new" product for the new Norton company, even if they represent the end of the line for the 961.
TVS-Norton will have to support these final units, like any other product that they push out the door.
There may have already been fixes in the pipeline for many of the 961's foibles when the plug was pulled on SG.
Maybe these fixes were never introduced by SG because they would have cost too much.
I think there will be some improvements on these final 961s, just nothing really significant.
That would involve a greater investment in development than I think TVS wants to make in a discontinued model.

Finishing off these last few units for customers is TVS's want of building that well of positive customer opinion.
Click to expand...
Question,
After Our experience with the 961,all years ,would you spend your hard earned on another type of TVS Norton?
 
Guess some of these guys will find their way onto Access Norton (sorta modern) and we’ll find out directly whether the same problems are present. They will likely come looking for the same old fixes If that is the case.
 
MAK said:
Question,
After Our experience with the 961,all years ,would you spend your hard earned on another type of TVS Norton?
Click to expand...
After my 7 year experience with the 961, I would consider another Norton if:

1. If there was shared risk - If there was a US dealer crazy enough to become a Norton dealer, and be located reasonable close to me so I could be assured that my warranty work would get done, and parts would be available.

2. If the new Norton company introduced a model that was to my liking. The new 650s as currently designed, are of no interest to me. a V4 1200 Superbike with clip-ons, crotch rocket ergos, also is of no interest to me.

Now if Norton introduce a new Modern Classic twin like the 961. but obviously with a new well engineered engine - that would get my attention.
Even a reworked V4 to be more of a standard street bike, or hooligan bike with good ergos, handlebars, but a shit load of HP - SCHWING , I'm in.
 
MAK said:
Be interesting to see what TVS do with the last batch of 961s.
They can’t leave the door with the same recognised faults ,Can they!!
Click to expand...
Had mine coming up 1 year so presumably one of the last Mk. 2s. No problems just looking to release some potential.
 
BritTwit said:
I am a carb guy so I would find this wonderful too.
However, adapting new throttle bodies, and retaining the stock EFI would be much simpler.

Don't forget the EFI system not only supplies the fuel pulse to the injectors, it also controls the ignition timing.
If you mount carbs, and bypass the electronic fuel control, how will the ignition pulse be controlled?
Carbs will dump a whole lot of fuel into the system, with a whole lot more ending up in the exhaust.
That will make the O2 sensors cause the ECU to screw with the ignition pulses trying to adjust combustion.
Also, the temp sensor data will force the ECU to make ignition changes as well,
This will not be optimal for a carb-ed engine.

The best outcome for a carb-ed engine would be to fit a separate ignition module, preferably one that allows tuning. Like the igniter box used on the Hinckley carb-ed Triumph Bonneville line prior to 2016. The igniter uses a transducer and timing ring, like the 961 has, and should be adaptable to the 961. The igniter box also has inputs for TPS, sidestand switch, clutch switch, and kill switch. The box has output signals for ignition coils, and tach signal.

So:

1. Fit new throttle bodies, and remove airbox and fit foam air filters. dyno tune the motor, done.
2. Fit new carbs and either:
a. Screw with the EFI system to get the ignition to work properly with the new fuel flow from the carbs, and the sensor data it produces.
or
b. Bypass the ECU ignition completely and install a different ignition module, and get it all to work together.The
Click to expand...
LPG kits fitted to EFI cars have injector emulators fitted that are pulled into circuit when the car is switched over to LPG from petrol. The ECU still thinks it's controlling the injectors, easy to come up with similar for 961.
BritTwit said:
kits fitted
Click to expand...
 
Voodooo said:
Why would they possibly spend time, money or effort on the 961 when it’s all over.
Click to expand...
Perhaps they'll do a Citroen and try and buy them all back :-)

'The sales were so disappointing that Citroën attempted to buy back and scrap each Birotor, as it did not want to support the model with spare parts. A few of these remarkable vehicles have nonetheless survived in the hands of collectors, many without titles for some time as Citroën did not want to recognize the cars.'
 

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