Commando cylinders upright like an Atlas

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YukoNorton

YukoNorton

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I think this is a different one. I picked up a basket 1974 850 Commando, engine vin starts with 309... The engine, cradle and gearbox are together in the frame, and the top end is fresh, not been fired.
The engine is not canted forward like a typical Commando, but close to vertical like an Atlas. I popped off the primary cover and can see a previous owner slotted the three inner primary to crankcase bolts, rotated the inner primary counterclockwise, so now the cylinders are near vertical when primary is horizontal.
The gearbox cradle looks original, but I am wondering if it is an original for an Atlas engine.
Is that possible to mount an Alas gearbox cradle to a Commando engine? Can I find a part number on the gearbox cradle?
I don't know why this was done.
 
Even when the Commando first came out and was available to the GP, they used the 750 Atlas engine suitably modified to be canted forward.
Maybe some PO had an engine blow up and an Atlas was available.
The only way you'll find out is to look at and remove the timming cover to see if the Atlas oilways are in there, the cylinder head removed to see if there is a spigot on the barrels.
Have you got a rev counter gearbox on the timing cover?
 
Maybe someone had the motor mounted in a Featherbed frame, my 850 is in a FB frame but I have my motor tilted forward and us my own engine plates.

Ashley
 
Bernhard said:
Maybe some PO had an engine blow up and an Atlas was available.
Click to expand...

Then it shouldn't have a '309' engine number.


YukoNorton said:
The gearbox cradle looks original, but I am wondering if it is an original for an Atlas engine.
Is that possible to mount an Alas gearbox cradle to a Commando engine? Can I find a part number on the gearbox cradle?
Click to expand...

The Atlas didn't have a "cradle".
andover-norton.co.uk

Andover Norton Parts Drawings - Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
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andover-norton.co.uk

Motorcycle parts and spares for Norton motorbikes - Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Factory Spare Parts for Norton motorcycles built before 2002.
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Last edited:
As the comment above suggests that the only way to make confirm your diagnosis is to supply lots of photos.
 
Thanks guys. It is a 850 Commando engine.

Maybe the guy modified the cradle by drilling new middle and upper engine mounting holes in the cradle to tilt the engine more upright.

Can someone provide the measurement; from the top engine mounting hole to middle of rear isolastic?
I have approx. 8-5/8" center to centre; top engine mount bolt to center rear isolastic, and 7-3/4" from outside diameter of isloastic to centre to engine mounting bolt.
 
YukoNorton said:
Maybe the guy modified the cradle by drilling new middle and upper engine mounting holes in the cradle to tilt the engine more upright.
Click to expand...

Pivoting the engine on the lower mounting would alter the crank to gearbox shaft centre distance and, as you said previously...

YukoNorton said:
I popped off the primary cover and can see a previous owner slotted the three inner primary to crankcase bolts, rotated the inner primary counterclockwise,
Click to expand...
 
ashman said:
Maybe someone had the motor mounted in a Featherbed frame, my 850 is in a FB frame but I have my motor tilted forward and us my own engine plates.
Click to expand...
ashman: Did you have to modify the cradle to change the cant of the cylinders? or is the motor just tilted forward? I remember seeing an article on a Commando in a Featherbed frame...and featherlastic posts on here too.

www.cycleworld.com

Building the Perfect Norton Motorcycle—From The Archives

Norton never combined the two best qualities of its bikes: the legendary handling of the Featherbed frame and the smoothness provided by the Commando’s Isolastic rubber engine mounts... enter the Featherlastic.
www.cycleworld.com www.cycleworld.com
 
YukoNorton said:
ashman: Did you have to modify the cradle to change the cant of the cylinders?
Click to expand...

Ash doesn’t have a cradle, he has his motor in a featherbed frame mounted using engine plates as he said “my 850 is in a FB frame but I have my motor tilted forward and us my own engine plates”.
 
I cut the original Commando rear engine cradle and mounted my motor where I wanted it then add bits to the Commando plates to fit the Featherbed frame by welding the added bits, I ran these plate for a few years till I made my own 5mm engine plates and for easier gear box removal as well a bit lighter, I still have the Commando/Featherbed plates hang in my shed, I also have a set of alloy engine plates I made but they were also made out of 5mm plate and found they vibrated more so went back to the 5mm steel plates, the saving of weight really was much so stuck with the steel plates, its been like this now for over 38 years.
There are pics on this site of my engine plates that I made and installed just got to go back about 10 years lol.

Ashley
 
With the Commando motor leaning forward in the FB frame, the bike will handle better because the weight will be further forward. Most Tritons feel lighter in the front than a Manx, and never handle as well. The weight in the front affects the way the bike feels when you accelerate leaning over. A Manx feels much more positive which inspires more confidence. The Commando engine in the FB frame would be very good, when you ride it fast.
If I had a normal Commando, I would prefer to have the engine leaning forward rather than upright.
 
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