Engines with the 'Combat' type crankcases are easy to recognize, not only by their engine number, which is in the 200.000s, but furthermore by these being the only Norton twin crankcases that do not have the big filter screw at the bottom. Plus, if they have not been modified, they have a breather tower bolted to the rear of the crankcase, between crankcase and gearbox shell.
Norton folklore wants it these engine suffered from the high performance wrung from them. The gullible Norton fans seriously believe the 'Combat' engines had 65bhp, explaining why things tended to fly apart. Not only is the performance figure one of the then common publicity lies, but performance was not the problem- the crankcase was.
Another reason given was the pre-Superblend bearings digging in. Whilst German Ex-Importer Koerner told us his shop introduced Norton to the 'Superblend' type bearing, I suspect the loss of oil was far more detrimental to engine life than the limited life span of the pre-Superblend bearings.
This new crankcase, and its breather arrangement, had been so cleverly redesigned for 1972 the sump was not drained properly at higher revs. Normally the problem starts from 4.000 to 4.500rpm upwards. As a result oil foam formed in the crankcase that was then thrown out of the breather, mostly unnoticed by the rider sitting in front of the breather outlet, until there was no oil left.
I have heard from owners of this engine type they never had a problem. However, having ridden a race engine on the track many years ago that- due to our ignorance of the problem at the time- sported an unmodified crankcase, I can tell you the oil literally pumped out of the breather and I put a good layer of oil onto the track, making myself highly unpopular with my fellow competitors!
As said above, the problem arises at higher revs and speeds. Not a problem for the American market at the time, with its speed limits, or the UK market with most of the roads at the time still winding though the countryside, pre-war style and standard. Very much a problem in Germany, with straight autobahns and no speed limits. The then German importer Gerd Koerner rebuilt 400 engines that year under warranty and his contract was terminated by Norton Motors because 'it must be his workshop's fault'.
Secretly, they knew what the problem was, and consequently issued a service information (below), no doubt written by the late John Hudson, who told me he visited Koerner to assist with the problem.
- Norton Commando 4 Brush Starter For Motorcycles For Sale
- Norton Commando 4 Brush Starter For Motorcycles Parts
The Norton Commando Ignition Switch is referred to as the Master Switch in the Workshop Manual.
Up until the MK3, it can be found above the left side footrest.
For the MK3 it was relocated to the Warning Light Console in front of the handlebars (the wiring is still the same though)
From 1972 onwards a four terminal, four position switch was used – Lucas Part Number LU30552.
The positions are:
- Parking with Lights (key removable)
- Off (key removable)
- Ignition Only (key captive)
- Ignition and Lights (key captive)
The numbers on the factory wiring diagram correspond to the numbers embossed on the bottom of the switch itself.
If there’s anything we love more than a classic racebike, it’s one with a good story behind it. And this gleaming Commando ‘S’ Roadster from NYC Norton comes with a very unusual history indeed. NYC Norton is run by the affable and knowledgeable Kenny Cummings. He knows his way around a racetrack as well as old Brit iron, and he’s pretty much seen it all. But the manner in which this. Heavy Duty Electric Starter Motor for Norton Commando. New replacement motor for the original Prestolite/Norton Starter. Features: Four brush, high driving torque motor. Ball bearings for efficient/easy spinning. O-ring sealed motor for gas and water exclusion. The Yuasa YTX20CH-BS (100 bucks on the web) is a 18 A-H sealed battery that provides 270 CCA. It will just fit in the Mk3 battery caddy. The CCA is crucial for reliable starting (Dave Comeau figures 300 Amps plus drawn at a cold start), so don't short this figure regardless of technology. 6 AWG and even 4 AWG wiring is available at any good marine supply house. Norton Motorcycles Information: Norton Motorcycles is a company that has been around since 1898. In the early years, they produced parts for all two-wheeled vehicles. It was 1902 when they began manufacturing racing motorcycles. They also added sidecar models for racing during the 1920s. During World War II, Norton Motorcycles stopped.
Here is an excerpt from the wiring diagram, showing the colour of the wires going in to the switch.
Here you can find the entire Norton Commando Wiring Diagram (there are many different versions on this website which will cover all years, as well as many of the popular upgrades)
One point worthy of note – Bill Turnbill produced a colour coded wiring diagram (from where my first ones were reproduced from with his kind permission)
Norton Commando 4 Brush Starter For Motorcycles For Sale
Bill’s diagram incorrectly labels terminals 3 and 4 (they are shown reversed on his diagram)
You will notice that the bottom of the Lucas LU30552 switch is numbered 1, 4, 2 and 3
Norton Commando 4 Brush Starter For Motorcycles Parts
So when you plug your cables in on the bike, be careful how this relates to the diagram (both mine as well as the ones in the factory workshop manual) which numbers 1, 4, 3 and 2.
- 1 NU (Brown and Blue)
- 4 UY (Blue and Yellow) – this is the single terminal
- 2 W (White)
- 3 NG (Brown and Green)
Hopefully this will help somebody!
Categories: motorcycles, Tech Articles