differences between commando and atlas crankshaft (2016)

baz · Nov 25, 2018

You blokes do realize this post is from July 2016?
Hopefully Piero will be sorted by now?

74ok · Nov 29, 2018

the new info is still related to the original atlas commando crank compatibility question & relevant to anyone looking for that info & finding this thread,

i had no idea the e start case/crank fit nothing else, or if the info i copy pasted & quoted from the e bay ad was correct

acotrel · Dec 2, 2018

Why rebalance the crank ? All the different balance factor does is put the vibration at a different place in the rev range. The Atlas crank will probably make the bike rock backwards and forwards when the motor is idling, but at high revs it will probably be even better than a Commando crank. - Stay away from car guys, if you are going to have your crank rebalanced. Find yourself somebody who has raced a Commando.

The Commando crank is obviously just an Atlas crank with a big hole bored into the bob-weight. The preoccupation with smooth running was about competing with CB750 Hondas. It is simply bullshit, an Atlas was still a very good bike. My bike has the motor rigidly mounted and the hole in the crank is filled with a steel plug, If you use the bike and keep the revs between 2000RPM and 7000 RPM, it is super-smooth. When it idles it rocks, but you don't normally idle your motor when you are riding your bike. The only benefit which might be derived from Isolastics as far as motor internals are concerned, is removal of the sudden stop in response to vibration. But they affect the way power is transmitted to the rear tyre and when the chain is at full stretch, the sudden stop is there anyway.. If I had a standard Commando, I would rebalance the crank to about 72%, because that is where the crank runs naturally smoother at moderately high revs.

bill · Dec 2, 2018

once again you are showing your TOTAL lack of knowledge of commandos. if you don't know it is better to listen to those that do know. as i was told you have 2 ears and 1 mouth for a reason.

acotrel said:
Why rebalance the crank ? All the different balance factor does is put the vibration at a different place in the rev range. The Atlas crank will probably make the bike rock backwards and forwards when the motor is idling, but at high revs it will probably be even better than a Commando crank. - Stay away from car guys, if you are going to have your crank rebalanced. Find yourself somebody who has raced a Commando.

The Commando crank is obviously just an Atlas crank with a big hole bored into the bob-weight. The preoccupation with smooth running was about competing with CB750 Hondas. It is simply bullshit, an Atlas was still a very good bike. My bike has the motor rigidly mounted and the hole in the crank is filled with a steel plug, If you use the bike and keep the revs between 2000RPM and 7000 RPM, it is super-smooth. When it idles it rocks, but you don't normally idle your motor when you are riding your bike. The only benefit which might be derived from Isolastics as far as motor internals are concerned, is removal of the sudden stop in response to vibration. But they affect the way power is transmitted to the rear tyre and when the chain is at full stretch, the sudden stop is there anyway.. If I had a standard Commando, I would rebalance the crank to about 72%, because that is where the crank runs naturally smoother at moderately high revs.

acotrel · Dec 2, 2018

I have a friend who was an A grade rider in the 60s and 70s. He eventually progressed to riding Yamaha TZ750s for a sponsor. He started racing with an Atlas and won several A grade races against genuine production race bikes. He still has that bike and it is a really lovely old thing. Better than any Honda CB750 ever was. In fact on a race circuit, it would make any CB750 look stupid.

acotrel · Dec 2, 2018

bill said:
once again you are showing your TOTAL lack of knowledge of commandos. if you don't know it is better to listen to those that do know. as i was told you have 2 ears and 1 mouth for a reason.

Why would you rebalance the crank, when you can simply use it as is ? In any motor, there is a balance factor at which the crank will run smoothly at moderate revs. The atlas crank is obviously right. The hole in the Commando crank is an abortionists' cure for vibration at low revs.

bill · Dec 2, 2018

maybe ? so on a short course but norton NEVER won a race like the daytona 200 from the late 60s on. yes the norton was a better handler but it comes to a point where you can never make up a horse power and reliability defacet on a long fast circuit.

acotrel said:
I have a friend who was an A grade rider in the 60s and 70s. He eventually progressed to riding Yamaha TZ750s for a sponsor. He started racing with an Atlas and won several A grade races against genuine production race bikes. He still has that bike and it is a really lovely old thing. Better than any Honda CB750 ever was. In fact on a race circuit, it would make any CB750 look stupid.

bill · Dec 2, 2018

again you show you havent a clue how the isolastics work. i am done talking with a fool

acotrel said:
Why would you rebalance the crank, when you can simply use it as is ? In any motor, there is a balance factor at which the crank will run smoothly at moderate revs. The atlas crank is obviously right. The hole in the Commando crank is an abortionists' cure for vibration at low revs.

acotrel · Dec 2, 2018

About the taper on the Commando crank. If you fit a single row dominator sprocket to the Commando crank and a dominator main shaft to the gearbox and a dominator clutch, the single row chain lines up perfectly. With Nortons, the adjustment for various motors is in the engine sprocket, not the crank taper or placement. I have three single row sprockets off various Norton motors which are all different from each other. Nortons are not Japanese, there is always a progression between models. The Japanese often do a complete redesign between models.

JimC · Dec 3, 2018

acotrel said:
About the taper on the Commando crank. If you fit a single row dominator sprocket to the Commando crank and a dominator main shaft to the gearbox and a dominator clutch, the single row chain lines up perfectly. With Nortons, the adjustment for various motors is in the engine sprocket, not the crank taper or placement. I have three single row sprockets off various Norton motors which are all different from each other. Nortons are not Japanese, there is always a progression between models. The Japanese often do a complete redesign between models.

Well, Norton did go out of business, whereas Yamaha, Honda, Suzuki and Kawasaki are stronger than ever. Norton would have been well served by a complete redesign back in the day.