1974 power options

Among the Norton Commandos sold in 1974, did the factory offer an engine with more torque or horsepower than the standard version?

No other than the noise reduction (power reduction as well) package fitted to the MK1A and MK2A for UK and Europe, not even the JPN replica which had the MK2A package included regardless of market.

Dump the black cap silencers fitted to the A's and replace with peashooter, up the main jets from 230 to 260 and you get the power back.

I

kommando said:

No other than the noise reduction (power reduction as well) package fitted to the MK1A and MK2A for UK and Europe, not even the JPN replica which had the MK2A package included regardless of market.

Dump the black cap silencers fitted to the A's and replace with peashooter, up the main jets from 230 to 260 and you get the power back.

Click to expand...

Is the OP alluding to the 'short stroke' 750 motor that was listed: 'Late '73' ??

EstuaryBoy said:

Is the OP alluding to the 'short stroke' 750 motor that was listed: 'Late '73' ??

Click to expand...

He has just bought an 850 74 Roadster, so very much doubt it.

kommando said:

He has just bought an 850 74 Roadster, so very much doubt it.

Click to expand...

Aha!! His post makes no mention of that......

Page 159 of this service sheet pdf outline the Factory recommended method of increasing the power.

1973 850 MODEL COMMANDO HIGH PERFORMANCE MODIFICATION INSTRUCTIONS


You had to do it yourself, it was not a showroom option.

Conversion instructions from Standard Road Specification to High Performance Sports Condition. The following components will require replacement or modification to achieve the recommended specification. 1. Camshaft replacement to ‘SS’ Sports specification. 2. Piston modification to Sports condition. 3. Cylinder head Conversion to Full Flow ‘High Compression condition. 4. New Amal Velocity Stacks for Carburettors. 5. Push rod modification. The accompanying instructions detail the alterations that are necessary to convert existing components to the recommended condition.

Sounds like a combat 850. I can understand why Norton would not offer it from them. It was OK to do if they didn’t have liability.

kommando said:

He has just bought an 850 74 Roadster, so very much doubt it.

Click to expand...

Correct, this is a 1974 Roadster. Thanks for the clarification.

ekuna said:

Among the Norton Commandos sold in 1974, did the factory offer an engine with more torque or horsepower than the standard version?

Click to expand...

Generally speaking, 1974 850's came equipped with the RH10 head, which has 30mm diameter intake ports and is less likely than the RH4 850 head to suffer from cracking near the valve guides (not positive whether inlet or exhaust guide areas are more likely to be affected). So if you have an RH10 head, which hasn't been adversely modified, and the rest of the bike is stock, you already have what is probably the best performing 850 that Norton produced.



These URL links will provide you more to read about the two different heads that most 850's were equipped with:

More power from power adders, in most cases, means less reliability. You can get more power with increased reliability by clearancing, head work and balancing; blue printing, but not taken to the OSD level.

The stock cam seems to favor low and mid range torque production. If you wish to move torque production up make sure it will fit your riding habits. The 2S came that is suggested in the material that kommando provided a link to seems to come alive a bit over 6000 RPM, from what I have read on this forum, and doesn't want to sign off until well above 7000.

Back "in the day" most Commando pilots would shift when the engine "ran out of breath", choosing to focus their attention on the road, smart move. You are more likely to be able to walk away from a blown engine than the radiator of a Mack truck.

Match your mods to your riding style and your expectations will be met more often than not.

Best.