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TT
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 Posted: Wed Jul 14, 2004 10:58 pm Post subject: Rubber Mounted Amals |
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Why are the AMALs rigidly mounted to the vibrating engine. It seems that this causes premature wear on all the components - particularly the slides.
When I rev my 850 on the centerstand the carb tickler dances around. I hate to think what else is moving internally.
Of course when I rev the bike on the centerstand the whole bike jumps backwards a couple of inches. It's called character!
Wouldn't rubber mounted cards be better? |
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Ron L
Joined: 27 Feb 2004
Posts: 1101
Location: Ohio
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| Posted: Thu Jul 15, 2004 3:30 am Post subject: |
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| Yes, Amal Mk II's and all modern carbs are rubber (spigot) mounted. The vibration is worsened by the isolastic mounting of the Commando engine. |
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Guest
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| Posted: Thu Jul 15, 2004 4:10 am Post subject: |
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TT,
You have a good question; I don't know why the AMAL carburetors are rigidly mounted to the Commando engine. I assume you mean why is it not mounted to the intake track in the head via a rubber transition piece like so many other non British bikes.
Rubber mounting the carburetors seems like a good idea to me.
Regards,
Jason |
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Philippe
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| Posted: Thu Jul 15, 2004 9:46 am Post subject: Car rubber mounting |
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I do not think it would be a good idea to rubber mount the Amals on a Norton as it would amplify the movement of the engine (even if it will filter the vibration). I remember a -82 FXR Harley on which I mounted a Mikuni (old type, not flat side) and it was handling only by the rubber: at idle the poor thing was jumping up and down! I guess in order to to this on a Commando a outside bracket would have to use to hold the carbs steady, while filtering the small vibrations that harms most the slide/bore.
Philippe
PS: has anyone thought of installing an old type HArley carb on a norton? They 36mm, not too big, not high as a Mikuni or a SU... |
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Ron L
Joined: 27 Feb 2004
Posts: 1101
Location: Ohio
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| Posted: Thu Jul 15, 2004 11:00 am Post subject: |
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| Single and dual Mikuni kits spigot mount the carb to the Commando with no ill effects. The oscillations are apparently not at the proper frequency to make them move "out of phase" with the engine. |
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MichaelB
Joined: 14 Jan 2004
Posts: 431
Location: Yorba Linda, CA
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| Posted: Thu Jul 15, 2004 11:57 am Post subject: |
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Interesting post.
I am not sure, but I think the Proddy racer runs em rubber mounted. I know Norvil sells 33mm smooth bores with rubber mounted manifolds. I have wondered why this is. When going for maximun performance, they go to rubber mounts.
I hadn't considered the vibration / oscillation movements, but had considered the heat transfer from the head. By rubber mounting, the carbs are insulated / isolated from the head, keeping the carbs cooler for better atomization. Maybe???
It seems the guys in the know run em rubber mounted. Does anyone have a good explanation?? |
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norbsa48503
Joined: 07 Apr 2004
Posts: 995
Location: Flint, Michigan
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| Posted: Thu Jul 15, 2004 1:43 pm Post subject: |
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| If you want to go the way of the rubber mount you may find the info in this old post interesting. RE;setting up Mark two’s on their Norton’s Just look it up under old posts. I hang my carbs from o-rings off the frame to releave the strain of the weight and dampen vibes. norbsa |
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Jason Curtiss
Joined: 14 Jun 2003
Posts: 661
Location: HOUSTON, TEXAS
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| Posted: Thu Jul 15, 2004 1:50 pm Post subject: |
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MichaelB,
I think you hit the nail on the head; all the go-fast guys rubber mount carbs. For instance, Paul Dunstall of Dunstall Norton fame rubber mounted the carburetors on his racers.
And yes, rubber does keep the carburetor cooler as well as dampen vibration.
Regards,
Jason |
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Norton Commando Forum by Corporate Pages Web hosting using phpbb
The Unapproachable Norton Commando
At the end of 1967 the Norton Commando was announced.
The Norton Commando was greeted with a certain amount of scepticism because on first sight the commando appeared to comprise of the old Norton Dominator twin cylinder engine mounted at an inclined angle in a set of new cylinder parts.
It was not realized that the new Norton Commando Isolastic method of engine suspension damped out all engine vibration and produced a machine which had uncanny smoothness for a vertical twin. In due course the critics were silenced and the Norton Commando had the distinction of being regarded as the first of todays so called superbikes. There can be little doubt that the original design concept of the Norton Commando has proved correct, since comparatively few modifications of any real consequence have been made since production commenced during 1968.
Now nearly 40 years later Norton Commando riders like us are a breed of our own, and as far as we are concerned its still more fun to go for a blat on the old Norton Commando, and fast. As a Norton Commando owner and enthusiast, my goal here is to promote and give credit to those who keep the Norton name going.
It is more deserving to give credit to the Commando itself, for after all these years it continues to be respected. The original Commando designers like John Favill are those who deserve the credit for developing this incredible motorcycle.
The Norton Commando Roadster and Interstate of the late seventies, never died. Although the Norton Villiers factory dispersed the tradition lived on. Today Kenny Dreer in the USA is developing the new 952 CC Norton. What a great looking bike this is, and its engineering is still based on the original layout. It will be interesting to see how the new 952CC Norton does in todays tough motorcycle market. One thing is for sure, I would own one if I could afford it.
