Commando engine question.

According to Roy Bacon in his book on the Commando, Norton used six different engines in the street bikes. Two were 77X89 850s with 8.5:1 compression and four were 750s. Of the 750s three were 73X89 with 8.5, 9.0, and 10.0:1 compression. He also describes a 77X80.4 with 10.5:1 compression fitted to the Roadster.

Now, I remember the long-stroke high-compression Combat Commando but I don’t remember seeing the short-stroke 750 bike. Was it called a Combat too?

Back then I remember there was a sensation because a stock Norton was outrunning the stock Z1s at the drag strip. Would that bike most likely have had the short stroke engine?

Murray B said:

Now, I remember the long-stroke high-compression Combat Commando but I don’t remember seeing the short-stroke 750 bike. Was it called a Combat too?

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No, the 750 short stroke was not a Combat. Some short stroke engines were produced mainly for racing, and not many found their way into road model chassis-even though the 750 "short stroke" model did appear in the 1973 brochure.
http://www.classicbike.biz/Norton/Broch ... LineUp.pdf

Murray B said:

Back then I remember there was a sensation because a stock Norton was outrunning the stock Z1s at the drag strip. Would that bike most likely have had the short stroke engine?

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That was probably Norman White on a standard [Edit] 750.
http://www.normanwhite.co.uk/profile.htm

short-stroke-750-for-sale-t11257.html

http://commando.yolasite.com/performance-mods.php

This sucker ran a 10 /5 or 11/5 . 18 in Dunlop KR 84 or the like on the rear. Series in M.C.N. on how to hot rod your Cnorton .

ANYONE got the original Script . Please .

Or Dave Rawlins on the Norton Villers factory modified 850 1973 Roadster.
Whose 1/4 mile times are mentioned in the 1974 Norton Brochure.
And which bike became the basis of the Stage 1 and Stage 2 Tuning Sheets put out by the factory.

L.A.B. said:

No, the 750 short stroke was not a Combat. Some short stroke engines were produced mainly for racing, and not many found their way into road model chassis-even though the 750 "short stroke" model did appear in the 1973 brochure.

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Thanks, that makes sense. They announced the machine but did not ship it so there are none for me to see. Of course in North America such a machine would have run afoul of legislation. Every single car I can think of had its compression reduced to 8.5:1 or so in late ’72 to meet the NOx emission standards. Norton seems to have done similar starting in with their ’73 models.

L.A.B. said:

That was probably Norman White on a standard 750.

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Yes, thank you, I had forgotten the name but that sounds about right. One bit on their site is poorly worded. The text, “As far as we know, this time has never been equalled on a stock Commando” makes it sound like there may have been cheating going on. Since stock Commandos could run 12.7 locally at higher altitude and temperature the 12.24 figure does not seem impossible. It is the Z1s I felt sorry for because they were often beaten up by their little 500cc brothers?

Matt Spencer said:

This sucker ran a 10 /5 or 11/5 . 18 in Dunlop KR 84 or the like on the rear. Series in M.C.N. on how to hot rod your Cnorton.

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Matt, you are like an encyclopedia of British bikes. Over the years I have read plenty but have not seen most of the things that you post. This stuff is really interesting and thanks for posting it.

Rohan said:

Or...

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Please do not respond to my questions again lest I become, “jingoistic and patronising”. It is a big forum and there is no reason for us to communicate again.

Funny, you were sprouting "truth" only a few moments ago.
The truth will out....

Matt Spencer said:

ANYONE got the original Script . Please .

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You mean the paper from which (most of) the drawings were taken? That is Norton Service release N3/73 "850 model Commando - "Stage one" high performance modifications" and N3/64 "850 model Commando - "Stage two" road racing conversion". They are floating around the net, one version taken from that Australian DVD is called 850_Stage_two_tuning.pdf, e.g.


Tim

Motor Cyle Machanics ,Magazine M.C.M. , the English one , & one American one perhaps , ran a few write ups .
Of which the Tech Notes / Drawings , were a part .
Explained the trials & Tribulations of extracting the performance .

Im sure there was a ' Stage Three , with the ' Norvil ' ( Dunstall ) Re angled intake , big valve , full hemi ( No Squishband )
Head . ( Essentially a ' 850 P.R. spec head ) near a 10 yr old item by then .
Fitted with this , the gears pulled in a bit ( 4 speed ) & the sticky rear eventually , got it down to 10 . 5 , if the recalls o.k.
with the 36 mm carbs . ridden to the strip . Santa Pod .

Stage 2 Tuning Sheet got a stock looking 850 to 142 mph average (bothway) speed, and was fairly comprehensive.
Dunstall put out that red booklet of tuning notes - but was it faster than the factory effort ?

http://www.youtube.com/watch?v=hw6HQOKZG5w

I've posted this before but hell you've got to see it again. The Commando looks near stock and goes like stink.
Cash

Mmmmmmm. Nice! That sounds good and is great to watch.

It isn't you on that Commando is it Dave?

Reggie said:

Mmmmmmm. Nice! That sounds good and is great to watch.

It isn't you on that Commando is it Dave?

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I would love to say it was, but no it's not me, boy! would I have liked to have a go.

Cash