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max600
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PostPosted: Tue Apr 13, 2004 5:29 am    Post subject: Norton frames Reply with quote

Against the advice of wiser folk, I have decided to build a 750 from parts as a weekend canyon rider and occasional vintage track day bike. I am having difficulty in selecting and locating a frame. My preference is to build a ’73 750. The ’73 frame for some reason seems to be in short supply and it seems that most ‘new’ frames are fabricated around the ’75 850 design. Will a ’74 or ’75 frame accept the ’73 750 motor, wheels [disk/drum], and triple tree which I already have restored and ready to go, without making any major modifications to the frame?

Thanks for any advice?
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MichaelB



Joined: 14 Jan 2004
Posts: 430
Location: Yorba Linda, CA

PostPosted: Tue Apr 13, 2004 6:30 am    Post subject: Reply with quote

The frames are the same. The differences are in the triple trees and the cradle /swingarm.
750 specs show a steeper rake than the 850, however the difference is in the triple trees, not the frame.
The 75 / Mark III has a different cradle for the Mark III drive train. It also has a reinforced swing arm. An earlier cradle will fit the Mark III frame and either swing arm will fit the earlier cradle.
The only real issue is you will need a non Mark III cradle to fit your drive train.

Correction: I just checked current stock numbers with Andover / Norton and Norvil and found the Mark III and Mark IIa frame have a different stock number than the rest. I don't know what the differences are and will have to differ to someone else. Sorry.
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Ron L



Joined: 27 Feb 2004
Posts: 1098
Location: Ohio

PostPosted: Tue Apr 13, 2004 11:58 am    Post subject: Reply with quote

If memory serves me right, the difference in 850 e-start and non-e-start frames is the gussets where the hinged seat mounts. You can use a non-e-start engine/trans and all the body parts on an e-start frame. However, if you use a non-e-start frame with and e-start seat, you don't have the gusset and hole for the seat lock.
As to the 750 vs 850, the steering head is raked out (I believe two degrees?) on the 850 frame, but the triple tree stem is angled to give the same wheelbase. In other words, use 850 trees with an 850 frame, 750 trees with a 750 frame to retain the same geometry. Mix and match and you may or may not see a slight difference in handling.

Ron L
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max600



Joined: 13 Apr 2004
Posts: 2
Location: Birmingham, AL

PostPosted: Thu Apr 15, 2004 5:08 am    Post subject: Reply with quote

Thanks for the great info. I probably would not have found out about the triple tree until I got the bike together and measured for spec. As luck would have it, I found a great '72 frame two days after my original posting. I hope to have a runner in time for fall rides in the blue ridge. I will keep the information though. I have the 'build it' bug as bad as I have the 'ride it' bug.
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norbsa48503



Joined: 07 Apr 2004
Posts: 995
Location: Flint, Michigan

PostPosted: Thu Apr 15, 2004 7:48 am    Post subject: Reply with quote

The 72 frame should serve you well. We always put longer gussets in the inside of the top shock mount to better support the rear loop. Just make it follow the piece already there but make it at least an inch and one half longer then weld over the old one with MIG for it's low heat. This loop is most always bent down from years of use and should be straightened before gussets or powder coating or painting is done. To me the best thing about a 72 frame is that the rear body work for a Fastback will still fit on these. The rear loop on later bikes is a half inch too wide. Also the 71 frame has that nasty side stand mount. norbsa If you like to read the timing on this couldn't be better .http://www.vintagenet.com/phantom/wsc.html
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Ron L



Joined: 27 Feb 2004
Posts: 1098
Location: Ohio

PostPosted: Fri Apr 16, 2004 2:59 am    Post subject: Reply with quote

>....>snip<.....To me the best thing about a 72 frame is that the rear >body work for a Fastback will still fit on these. The rear loop on later >bikes is a half inch too wide.....

I have heard this from several different people, including dynodave. I'm not sure this true. These bikes are thirty years old and the rear loop took a beating. Maybe they have just been bent and straightened, or maybe it was just bad quality control.

My '75 MkIII has worn a new old stock '70 fastback tailpiece for the last 10 years. I recently checked it on the other frames in my shop. Two '74's and two '73's. It fits all of them perfectly, just like my two '68/'69 tailsections. Coincidentally all the tailsections fit the '69 frames also.

Ron L
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norbsa48503



Joined: 07 Apr 2004
Posts: 995
Location: Flint, Michigan

PostPosted: Fri Apr 16, 2004 6:01 am    Post subject: rear hoop Reply with quote

We checked Three frames from 72 and back and 3 from 73, 74. the difference was about one half inch wider on the later models. We were checking about sixteen inches back from the maim cross bar cause this is were the tightness is. There was a stamped number on the frame of these later bikes so I am thinking that these were the Itailian made. You might check your frame for stamped numbers if it has none this problem of a too wide could be Itailian. norbsa
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dynodave



Joined: 28 May 2003
Posts: 139
Location: USA

PostPosted: Fri Apr 16, 2004 1:23 pm    Post subject: Reply with quote

Arrow .

Last edited by dynodave on Mon Apr 11, 2005 5:20 pm; edited 1 time in total
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norbsa48503



Joined: 07 Apr 2004
Posts: 995
Location: Flint, Michigan

PostPosted: Sat Apr 17, 2004 7:36 pm    Post subject: Reply with quote

Thanks Dave, I am fighting with this right now trying to find a good way to bend this back to a norrower loop without distroying the fresh powder coat. So far Iam looking for some two inch channel iron that could be rubber lined and clearance drilled for half inch running rod above and below the tubing. this would be used to crush the rear loop to the just the little bit I need. Ever tried any thing like this? I am determined to get this to work and never thought to check the fit out before getting this far. norbsa
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dynodave



Joined: 28 May 2003
Posts: 139
Location: USA

PostPosted: Sun Apr 18, 2004 3:12 am    Post subject: Reply with quote

Arrow
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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.