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#67938 - 01/26/07 3:44 pm commando engine into atlas frame  
Joined: Sep 2006
Posts: 156
marinatlas Offline
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marinatlas  Offline
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Posts: 156
FRANCE- DINARD -BRITTANY
hello again !! in fancy to fit a Commando engine into an Atlas frame (because no atlas engine !! good reason), and like to detune it it by fitting a compression plate , single carb , have it balance to 84 %, any more ideas ? on the same way because the cases were from 200.000 and with the breather at the bottom , want to modify them as said previously; except that the norton logo will tilted up and not in line as the engine will be upright (try to mill it, to get a smooth cover........

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#67940 - 01/27/07 11:00 am Re: commando engine into atlas frame  
Joined: Oct 2006
Posts: 187
coz Offline
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coz  Offline
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Joined: Oct 2006
Posts: 187
MA USA
as long as you have it balanced there is no need to go with the featherlastics system. you also dont need to mount it upright. Buy some engine plates and bolt it right in. Why would you detune it?
http://www.caferace.com/cafepix9.html
here is a link of a commando in featherbed. scroll down youll see it.

#67941 - 02/01/07 4:58 pm Re: commando engine into atlas frame  
Joined: Nov 2006
Posts: 9
John Ebert Offline
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John Ebert  Offline
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Joined: Nov 2006
Posts: 9
Phoenix, Arizona
Several of my friends have fitted Commando engines into a featherbed frame with isolastic mounts. They refer to them as fetherlastics.
AMR in Tucson did most of the work on them and you could contact them and see what it involved.

#67942 - 02/01/07 8:05 pm Re: commando engine into atlas frame  
Joined: Jul 2003
Posts: 124
Brithit Offline
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Brithit  Offline
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Joined: Jul 2003
Posts: 124
Nebraska, jealous?
Here is a very detailed article by BillyBob Cox, and his Featherlastic. Info about how he dealt with chain alignment:

http://www.ntnoa.org/bobcox.htm

I've run into him on some other sites, and seems like a good guy who knows a thing or two.


Don W.

'69 Trident - U.S. Variant
Nortons: '72 Combat ' 75 Interstate
'59 Velocette Venom Clubman
#67943 - 02/06/07 9:51 pm Re: commando engine into atlas frame  
Joined: May 2004
Posts: 557
jangg Offline
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jangg  Offline
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Joined: May 2004
Posts: 557
Norway, just south of Oslo
According to my sources ("Norton Commando" by Mick Duckworth) the "Commando project" got Norton's "745cc Atlas Engine". - So the "original Commando engine" is the 745cc Atlas one. "It's strong performance came at the cost of uncomfortable and destructive vibration"...

The Commando 745cc engine (the "750 Commando") was a true Atlas heritage ("straight line"). The 750 Commando entrance got a 65% balance factor though - satisfactory due to the patented Isolastics System.
But a (750) Cdo engine in an Atlas shouldn't be a problem - except for some vibrations of course. Anyway The Featherbed will guarantee the handling.

Good luck!

regards
jangg


'73 Commando Basket - new aluminium cyl
'93 Ducati 900 SS

"Better lit a light than cursing the darkness"
(Confucius)
#67944 - 02/07/07 1:28 am Re: commando engine into atlas frame  
Joined: Nov 2001
Posts: 59
NYroadrocket Offline
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NYroadrocket  Offline
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Posts: 59
New York
As a streetbike, featherbeds are worthless. I built a 66 Atlas which was a total paintshaker at 4500 rpms in top gear (just where you want to ride it). On the racetrack is another thing.

Balance factor is the vital tool. it will never remove the vibes, but can put them lower in the rev-range. A Commando in a featherbed should be balanced to 84% just like an Atlas motor.

My new Seeley racebike crank is balanced to 89% to keep the upper rpm's clear.


Jordan
Team Incomplete
AHRMA, USCRA, VRRA, WERA #719
1972 Seeley Commando F750
http://www.nycseeley.com
#67945 - 02/07/07 8:30 am Re: commando engine into atlas frame  
Joined: Sep 2006
Posts: 156
marinatlas Offline
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marinatlas  Offline
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Joined: Sep 2006
Posts: 156
FRANCE- DINARD -BRITTANY
I have read with lot of attention , all those comments, and to clear the situation , YES I will rebalance the cranckshaft , should be sensible to copy the Atlas factor of 84% , (furthermore the engine will be upright and not tilted ,so we stay in the Atlas group of vibration ...), someone in the NOC forum speak about 65% like 650 cc Norton,what I want is to sweet up the engine in the low revs till 5000rpm, so I will detune the commando by fitting a compression plate (plus two paper base gasket)and may be simple carb (any comments, because Les Emery, once told me that with a single pipe the flow is not always that equal and one cylinder sucks more than the other thus unbalancing compression stroke), I had allready match the weight on rods and pistons , what's more ...?

#67947 - 02/07/07 10:57 pm Re: commando engine into atlas frame  
Joined: Aug 2001
Posts: 1,253
Dave Comeau Offline
Crew Chief
Dave Comeau  Offline

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Joined: Aug 2001
Posts: 1,253
Hamilton, Mass. USA
I thought the compression plates are to "adjust" the compression ....which always goes DOWN. I would call them DE-compression plates.
Effect on vibration? IMO... Not much.
The atlas pistons are about 26gms (about 1 oz.)each- LESS- than commando pistons. or about 12%


dynodave
BSA 3 1961-1963
Ducati 3 1992-2002
Norton many 1951-1975
87 Serv-Equip 100HP MC brake dynamometer,
#67949 - 02/08/07 12:17 pm Re: commando engine into atlas frame  
Joined: Sep 2002
Posts: 487
ludwig Offline
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ludwig  Offline
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Joined: Sep 2002
Posts: 487
belgium
Marinatlas , I suppose that by "compression plate" you mean a 2 mm thick alu head gasket to reduce compression ?
It may cause more problems than it will solve :
1. you will need longer push rods .
2. unlikely you will get it to seal properly .
3. the already too short 3 cyl. head studs will even have less threads for the nuts to hold on .
4. it will do nothing to reduce vibration .
If you absolutely want to reduce compression , try to find the original concave Atlas pistons , or , if you dare , remove 1 mm of the crown of the pistons .
To effectively reduce vibration you should find (have made ?) much lighter pistons , say , less than 300g .and rebalance accordingly .
If you DO find them , please let me know !
If you absolutely insist on installing a (de)compression plate and can't find it , I have one lying arround .
I'll mail it to you for free .

#67950 - 02/08/07 12:25 pm Re: commando engine into atlas frame  
Joined: Dec 2004
Posts: 8,887
kommando Online content
kommando  Online Content


Joined: Dec 2004
Posts: 8,887
Scotland
Have the compression plate as an extra cylinder base gasket, no issues with head to barrel dimesions but the push-rods will still need to be lengthened.

#67951 - 02/08/07 12:54 pm Re: commando engine into atlas frame  
Joined: Aug 2001
Posts: 1,253
Dave Comeau Offline
Crew Chief
Dave Comeau  Offline

Crew Chief

Joined: Aug 2001
Posts: 1,253
Hamilton, Mass. USA
Decompression plate offered by norvil:
066591 PLATE - COMPRESSION - STEEL - 1.00MM THICK - 750, 850 & 920 - NORVIL C D - - 6.70


This is a cylinder base plate NOT a thick head gasket. I bought one from the genuine norton supply line and was not impressed with the quality so I made my own out of .034" stainless.
I have not heard of, or looked for a source for thick head gaskets. I probably would not use one either.
Use a hot rod cam, and you don't have to shorten the pushrods. In my view, most people quote "the short push rods are to acomodate the shortened head of a combat", yet I feel it is as much for the cams much higher lift...but few if any mention that. sleep
Low compression and a hot rod cam? frown


dynodave
BSA 3 1961-1963
Ducati 3 1992-2002
Norton many 1951-1975
87 Serv-Equip 100HP MC brake dynamometer,
#67952 - 02/08/07 1:47 pm Re: commando engine into atlas frame  
Joined: Sep 2002
Posts: 487
ludwig Offline
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ludwig  Offline
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Posts: 487
belgium
these thick alu head gaskets , as I have one here in my hand , where sold by either Dunstall or Gus Kuhn . It's so long ago I can't even remember why or for which bike I bought it .
anyway , I never used it .

#67953 - 02/08/07 3:27 pm Re: commando engine into atlas frame  
Joined: Sep 2006
Posts: 156
marinatlas Offline
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marinatlas  Offline
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Joined: Sep 2006
Posts: 156
FRANCE- DINARD -BRITTANY
hello again everybody! I like Norton and furthermore I am not a proud engineer, just a sunday mechanic.

So, the plate I was talking about was the 1mm thick decompression plate to put under barrels , in order to reduce the compression, when using std commando pistons,as say Ludwig I could try to remove 1mm from the GPM piston crown if they are thick enough, any comments about the single carb versus the twin? have a nice day Pierre

#67954 - 02/13/07 3:33 am Re: commando engine into atlas frame  
Joined: Nov 2001
Posts: 59
NYroadrocket Offline
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NYroadrocket  Offline
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Joined: Nov 2001
Posts: 59
New York
Quote:
Originally posted by 69 mercury 750:
quote: "As a streetbike, featherbeds are worthless"
Oh that's a good one. I'll take yours off your hands if you like. anytime. My Atlas is a street bike, and I wouldn't part with it for all the tea in China. What pistons were you using? The original concave low comp ones make my bike a smooth runner, the C'do ones probably increase the vibes, but worthless???? I don't think so
just my two cents, Gary
Gary,

My Atlas was a fully tuned and blueprinted motor. I just found at modern highway speeds that it was close to unridable in comparison to my Guzzi V7 Sport or other vintage bikes I have owned.


Jordan
Team Incomplete
AHRMA, USCRA, VRRA, WERA #719
1972 Seeley Commando F750
http://www.nycseeley.com
#67955 - 02/13/07 8:11 am Re: commando engine into atlas frame  
Joined: Sep 2006
Posts: 156
marinatlas Offline
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marinatlas  Offline
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Joined: Sep 2006
Posts: 156
FRANCE- DINARD -BRITTANY
We are back to the problem, how to sweet the vibes ?
-1: match the reciprocating weights(rods and pistons).
-2: rebalance the commando cranck to Atlas factor(84% ?).
-3:reduce the pistons weight and/or reduce the compression ratio (by fitting Atlas 7.5/1 pistons which are unobtainable, or fitting the DE-compression plate under cylinder base).
-4:general De-tune: std camshaft,one carb versus two, 30mm inlet versus 32mm.
-5:beltdrive.
-6:anymore ideas...

#67956 - 02/13/07 11:42 pm Re: commando engine into atlas frame  
Joined: Aug 2001
Posts: 1,253
Dave Comeau Offline
Crew Chief
Dave Comeau  Offline

Crew Chief

Joined: Aug 2001
Posts: 1,253
Hamilton, Mass. USA
Quote:
Originally posted by marinatlas:
We are back to the problem, how to sweet the vibes ?

-2: rebalance the commando crank to Atlas factor(84% ?).
-3:reduce the pistons weight

As the piston weight comes down (and upper end of the rod and especially the wrist pin!!!).....the mass relating to 84% number comes down also. To me the rest doesn't matter. High compression only matters when you open the throttle....same with carbs. At highway speed you only need 12HP and you will only make enough pressure to make 12hp no matter what carbs, cam or pistons you have. The vibration is entirely RPM and mass(of imbalance) related, until you open the throttle.


dynodave
BSA 3 1961-1963
Ducati 3 1992-2002
Norton many 1951-1975
87 Serv-Equip 100HP MC brake dynamometer,

Moderated by  Dave Comeau 


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