Norton Commando 1969 Operating and maintenance manual

COMMANDO
SERVICE
NOTES
COMPLETE WITH ELECTRIC START
Text - Tim Stevens, John Hudson
Editor -- Alan Osborn

One of the most popular, the 750 Interstate 1973, with Combat engine, signified by black barrels.
Photo credit: Motor Cycle

CONTENTS
Introduction and Spares Officers 2
Engine numbers-model changes 3
Group 1 :-- Crank assembly including pistons, camshaft and timing
gear. 4
Grou
p
2:-- Barrels
,
g
askets and head
p
arts. 7
Group 3: -- Timing cover, all therein and rocker feed. 10
Group 4:-- Crankcases, breathing and main bearings. 13
Groups 5, 6, 7:-- Gearbox. 15
Group 8:-- Primary case and clutch. 18
Group 9:-- Carburetors. 21
Group l0:-- Engine mountings. 22
Group 11:-- Frame. swinging arm and suspension. 24
Group I2:-- Footrest plates. 27
Group 13:-- The oil tank. 28
Groups !4, 15, 16:-- Forks and front wheel. 29
Group 17:-- Rear hub, brake and sprocket. 30
Group 18:-- Handlebar controls. 31
Groups 19, 21-24, 28:-- Handlebars, side panels, front mudguard, scats, rear
mudguard, tanks and instruments. 32
Group 20:-- Exhaust systems. 32
Grou
p
s 25, 26, 27:-- Electrics. 32
Group 29:-- The tool kit. 32
Addendum 33
Further model changes 33
Engine, main bearings, timing chest contents, ex valves 34
Pushrods Primary chain case, Clutch slip 34
Clutch drag, Alternators, Electric start 35
Gearbox, Kick start pawl, The pawl spring 36-37
Go-faster mods etc. wheels and brakes, Frame parts and handling 38
Service Release N3,13 Camshafts 39
Some tunin
g
ti
p
s 40
Carburetor setting 41
Carburetion 42
Oil 43
The Norton Owners Club 1979. All rights reserved. No part of this publication may be reproduced, stored
in a retrieval system, or transmitted in any way or form or by any means, electronic, mechanical,
photocopying recording or otherwise, without the prior permission of the Norton Owners Club. So there! ©
Addendum 1980

SERVICE NOTES ON THE NORTON COMMANDO
Covering all models up to and including Mk. IlI
Original Text: T. R. Stevens Collation: AI Osborn
These service notes are based on the parts list and are intended to supplement it and the workshop manual. They
were written by Mr. T.R. Stevens for the club magazine Roadholder, and appeared in it from Sept/Oct '74 to May/
June '77, he group numbers referring to the groups in the parts list. When collating these notes I have taken the
opportunity to edit and update them where time and experience have dictated improvements. Further assistance from
T.R.S. and Mr L. Emery being used, while not inconsiderable extra notes have been added by our President Mr. J.
Hudson.
Mr T. R. Stevens was Quality Engineer and then Service Engineer at Norton Villiers Andover 1970-74, he is at
present lecturer in Motorcycle Engineering at Merton Technical College.
John Hudson worked with the Norton Development Shop from 23rd January 1955, initially as a fitter tester, finally
leaving the NVT complex in the summer of 1976 at its abolition. Voted as Life Honorary Member of the Club and
President for the second time in Sept 1970.
Les Emery, member of NOC since 1971, rose to National Committee in 1973 as Membership Secretary. He then
took charge of the spares scheme with regard to the twin cylinder machines.
Al Osborn joined the Club in 1970 rising to National Committee level as Assistant Editor in 1972, later becoming
Chairman from 1974-77.
SPARES SERVICE
Les Emery. 37 Albion Street. Rugeley. 5tatfs. Tel: [phone].
T.R.S, Test-rides a Fastback.
Diagram; by T.R.S. and Richard Graham (North London).
Front cover:- 1971 Fastback
Rear cover:- 1972 Fastback. now with Roadster upswept exhaust system.
The opinions contained (in these service notes are entirely -those of the authors. They have no endorsement from
any Norton factory, N.V.T., Norton Andover. or any such organization.
Notes in italics have been added for this edition by Alan Osborn, 9 Chapel Road, W. Ealing. London, W.13, from
whom further copies are available.
2

THE MOST SIGNIFICANT CHANGES IN THE MANY COMMANDO MODELS
Engine Nos.
126,125 FIRST COMMANDO, 17E(3 'G4. Silver tank, panels and frame-orange (!1 seat. Green blob on tank.
131,180 Now called FASTBACK, Conventional color scheme. Gusset below head-stock replaced by horizontal
bracing tube (under tank). (The first frames broke).
131,257 First "S" type made for American market. Smaller rounded (Roadster type) tank. High level parallel PIPES
left hand side, with reverse cone shape silencers. Points on the end of the cam shaft, REV. counter drive
inboard. Six volt coils with ballast resistor, 1971.
133,668 FASTBACK receives "S" type technical mods. Points, coils, etc. 135,140 First ROADSTER with low
pipes, upswept silencers, reverse cone absorption type.
139,571 FASTBACK Mk II fitted with Roadster exhaust system.
142,534 Mk II ROADSTER, Mk 111 FASTBACK, same 4:10 tyres on both wheels. Fork gaiters and F/bed type
yokes dropped, bare chrome stanchions introduced. Lucas h/bar lever switches introduced and indicators.
Centre stand mounted on g/box Shock absorber fitted in rear wheel.
Jan, '72 Consecutive engine numbers which had continued since W.W. II abandoned. New system and
numbers introduced.
200,001 FASTBACK Mk. IV, ROADSTER Mk. IV. New crankcase castings, with breather behind c/case (not from
end of camshaft). First double roller main bearings.
200,976 First COMBAT engine. Compression ration raised to 10:1 by machining head, double S camshaft fitted.
Black barrel-. 32mm carbs. Disc brake right hand side behind fork leg, Models now 'Fastback' and
'Roadster.'
212,278 INTERSTATE. Larger black or blue (5 gal) tank, seat longer. Low level Interstate silencers. (Most Combat
engines were later modified to standard engine specification and stronger main bearings fitted, i.e.
Superblends (barreled rollers). Small sump plug introduced, later models with car type oil filter. 16H type
(pre-war) front brake shoes with speedo drive clearance no longer used in Commando rear wheel.
(Shame!).
220,000 COMBAT engine abandoned but 32mm carbs retained. Roadster Mk. V, Interstate Mk. V only. No more
Fastbacks. Black instrument pods.
230,000 Square rear light. Different fork geometry. Box section head steady. 230,935 Last 750 COMMANDO
(unless you know better.)
300,001 April '73, first 850 Mk. I. Barrel fixings altered, bronze clutch plates fitted, balance pipe in exhaust pipes.
Strengthened swinging arm. larger sump plug reintroduced.
306,591 Mk. IA. Larger, quiet air box and annular discharge (bean can) silencers. Candy apple red tank also
available. Chain guard plastic extension added. 2nd gear ratio raised by one tooth (to reduce noise
readings).
307,091 Slimmer Interstate tank, 4 1/2 gals approx.
307,311 850 Mk. IIA. Improved paint, 30mm ports but 32mm carbs (for flexibility). Various small detail mods.,
such as mud flaps, third sleeve gear bush added. Black and blue tanks dropped, red and a few "traditional"
silver tanks. Fork gaiters reintroduced and lower bars. Tach drive oil leak reduced (supposedly).
309,600 Larger, stronger kick start.
3

GROUP 1.- Crank assembly inc. pistons, camshaft and timing gear
CON RODS: Con rods don't usually give trouble -- the unbushed little-end never wears and trouble at the big end can
usually be traced to a fault elsewhere, particularly running out of oil. Rods should be free from nicks and deep scratches
especially up the sides from the bolt holes. Fatigue life can be improved by shot-peening, but this is only important for
racing where stresses are much increased.
John Hudson: I have never seen dural rods shot-peened at the work:. For racing they were polished all over and if the
steel caps did not match the contour of the outside of the rod they were filed to shape before polishing.
Everyone misses a very important point in Norton con rod bolts -as supplied they have a razor sharp edge on the
underside of the head and this should be carefully filed off and the bolt rotated in lathe chuck or drilling machine and
the head polished with emery tape. Otherwise, the turning torque of the Phillidas nut causes this sharp edge to scrape a
shaving of dural off the side of the eccentric recess in the rod as the bolt is pulled down which, of course, then remains
under the head of the bolt and prevents its seating and tightening properly. This can have happened on original
assembly at the works, so whenever bolts are removed from the rods, check that there is not already a shaving in the -
bottom of the recess. > >
BIG ENDS: Big ends wear very slowly if oil is cared for. After a main bearing job the shells should be changed
because the hard bits of bearing circulating with the oil become embedded in the soft shells and can score the crank. At
the same time, of course. the crank should be dismantled and all the sludge scraped out.
CRANKSHAFTS: When having a crank reground specify in writing the size you want and the radius between the
crank pins and the webs (0.090in Rad, 2.25mm) then check that the work has been carried out properly before
reassembling.
Crank breakages can generally be placed to a radius too small-and not necessarily on a reground crank. New cranks
have broken at fairly low mileages because of tight radii - particularly around the drive-side main bearing. Even cracks
across the webs can start at the junction of the crankpin and web. Be careful too, when removing main bearing inners
by the traditional chisel method - nicks in the crank are just as bad as tight radii. Rig end bolts need not be replaced,
unless you are going racing; a tried and tested bolt is better than a new one which might fail.
Nuts should be used once only and not over tightened (or under tightened) If a nut comes off or a bolt breaks, it is
usually due to lack of lubrication - - you will see that the rod around the big end eye is brown in color if this is the case,
because -the hem generated when the oil supply ceased burns oil mist into the rod. The hammering after the big end
has gone will break bolts or loosen nuts very quickly, so -if you should have a motor nip up, always check the oil
supply before re-starting--there must be oil both in the tank and returning properly. Oil can be there but the pump
seized or an oilway blocked, and to continue would soon result in your own exploded view.
Before reassembling check the fit of the small timing pinion on the crank -the crank can be eased with emery cloth until
this is an easy push fit. The oil pump worm will hold it tight and it will make the next rebuild much quicker, as you
won't have to remember to whom you last lent your extractor (or where you borrowed one . . .).
4

IDLER GEAR SPINDLE: The spindle for the idler gear (that's the one that is both sprocket and pinion) should be tight
in the cases. If not, dry the cases off thoroughly and warm with a blowlamp before refitting the spindle with a drop or
two of "Bearing fit" loctite If it has been turning and will push in cold, copper plate it to a thou or two of interference
and try again (Have about five thou plated on and rub dawn to the required size with worn-out emery. Nickel or chrome
are too hard to rub down like this and must be ground to size). The oil hole goes underneath with the slot in the outer
end horizontal.
This spindle has been slack on my 1970 motor for yonks to no ill effect. Makes cam chain tension a bit awkward
to get right though. Case cracked open about 3/16in and a dabble and tug with a bent bicycle spoke (the same
one 1 use for push rod aligning) usually gets the problem sorted.
CAMSHAFTS: The later camshafts are tuftrided –a process which gives hardness without losing toughness. It can be
recognized by an even brownish grey color all over the shaft. Many dealers may still have earlier shafts on which the
cams are bright and these are not so good. so if you are after a cam, shop around. Avoid the SS cam like the plague--it
is nothing but trouble in a road bike and is slower than the ordinary cam (which was, after all, the grind used for those
650 production wins at Thruxton -- you remember, in the good old days when Notions won races), It is a good plan to
ease the end of the cam where the sprocket fits, so that this too can be pulled off easily -the next time. Never hammer
the cam nut tight without a cutaway timing cover or all your work getting the idler spindle tight will he undone. Even
pressure is sufficient and will cause no trouble.
A box spanner is preferable here, as the nut is shallow and slightly recessed ; a ring will tend to slip.
The "SS" cam mentioned here is the Commando SS cam or double S as used in the Combat engine (Interstate) as
opposed to the Commando standard cam which stemmed from the 650 SS profile mentioned. Referred to as the
"SS" because of its origin. This standard cam profile is as used on tire Atlas as well, and is now reverted to for
the 850s.
CAM BUSHES: If you are unlucky enough to have a pair of cases with steel cam bushes (they are bronze faced. but
can be recognized by the X-shaped oil grooves in the bronze surface of the bush), you must use bronze faced thrust
washers each side of the timing side crankcase. Break off the tabs which locate the washers in the hole alongside the
bush or they will break off in use. They are exactly the right size to drop into the crankcase and pass up the oil return to
the oil pump, "is seizes the pump, stops the oil supply, and within a very few yards the evidence disappears through the
bottom of the crankcases. There is no sump filter on the 1972 crankcases, and these are the ones with the steel hushes.
Very clever,
Further if; the steel cam bushes with "X"' oil grooves. or scrolling - these may be used with a plain or scrolled
camshaft. On no account fit a plain camshaft in plain bushes. Plain bushes were fitted to early engines and are
now being used again.
PISTONS: Don't buy new pistons with a slot under the oil control ring. This slot was deleted to avoid the top coming
off the piston when the revs were kept up towards 7,000. Of course, the slotted pistons are OK for the man who never
goes over 5,000 rpm. The later type are identified as Combat Pistons in the parts list, but the only difference is this slot-
the compression height of combat (non slotted) and standard (slotted) pistons is identical. The higher ratio of the
Combat engine was achieved by planning 40 thou off the cylinder head.
Atlas pistons will fit straight into the 750 Commando giving the lower
5

Atlas ratio (a bit more under a Combat head) but use Hepolite Atlas pistons and try to get those without
the slot. It's not so critical with Atlas pistons because the combustion pressures are less and generally the
chap who fits Atlas pistons doesn't go wailing about at 7,000 rpm all day.
A final point about pistons early Commando pistons had a three piece oil control ring where the central
hart was U shaped in cross section. Later pistons, both slotted and combat. have a 3 piece oil ring of'
which the central part is circular in cross section, the two sides of the pressing are bent over until they
meet. The two types of ring arc not interchangeable as the depth of the groove for the oil ring is deeper in
(lie newer pistons. 1 !re old type rings are more difficult to fit in the bore than the new ones, and aren't so
good at oil control, so that's another reason for avoiding early-type pistons.
Rings last, on average, 25 - 30,000 miles. At this mileage the bores shouldn't be worn significantly and
new rings will restore your oil consumption If the bores are worn enough at this mileage it) need boring
then change your brand of oil (or, dare I say it, change your oil).
Greater ring wear will occur without air cleaners and also not having chrome top rings (often two cast
rings are supplied). In these cases oil consumption can get as high as 100 mpp when the handle is -well
wrung". Only tip l0 70,t)00 before new rings and 40,000 between rebores.
The 850 Mk 11A Roadster, complete with 'bean cans'.
STOP PRESS:
CLUTCH PLATES: If you change any early 750 clutch to phosphor bronze plates (although you'd do
better by changing the oil to Castrolite first. it's also cheaper) then you'll also need the hardened clutch
centre as well to help stop the bronze plates from notching in the centre. Part No. 063979 (Page 20).
GEARBOX 2ND GEAR: From Engine No. 306591 a new pair of 2nd gears were added 064639 and
064640 fully interchangeable with previous pairs 040418/040019 on no account mix the gears, pairs only.
The reason for the change? The factory said 'to provide a more graduated set of ratios' actually it was lo
up the ratios therefore lower the revs in 2nd gear to pass noise restrictions!
6

GROUP 2:- Barrels, gaskets and head parts
CYLINDER BASE GASKET: This was deleted from Mk. I and II 850, plastic gasket such as Loctite,
Hermetite RTV or similar silicone compound being used. A gasket was again introduced, part no. 0638
12, on the Mk. III as people filled the oil drain with RTV, causing lots of trouble. Removing the gasket puts
the compression ratio up by approx 0.3 of a ratio, see table. The 850 gasket can be used on the 750 but
not vice versa as the cylinder apertures aren't big enough. 750 base gasket is part no. NM24249 or
Q67869.
The silver and black 750 barrels are identical dimensionally and incidentally, the studs all round the base
are exactly the same positions on the 850, so you can build a 750 using 850 crankcases, but not the
other way round, because the holes for the downward extensions of the barrel aren't big enough.
CYLINDER HEAD GASKET: This is where the complications start! There are plain composition,
aluminum, copper and eyeletted composition gaskets for the 750 (and copper-asbestos, if you go back far
enough!). The composition gaskets are about .028in thick in use, the copper gaskets are about 0.040in
and the aluminum 0.O80in thick. I will leave you to work out what these do to the compression ratio with
the various heads available. Whatever compression ratio I wanted, I would use an eyeletted gasket. The
others are all suspect. (Mine has been perfectly satisfactory on standard compression i.e. 8.9:1. Anyway
the eyeletted one did cost 3 or 4 times as much). The plain composition causes pre-ignition, because the
reinforcing wires glow at the end, and then blow. The aluminum gasket squeezes out almost as quickly as
-the custard in a vanilla slice-so you can hardly keep up with tightening the head bolts. They also spread
into the push-rod holes and rub them away (even if they don't rub them from new). Copper and aluminum
seem incapable of maintaining an oil-tight joint around the push-rod holes. A smear of RTV in this area
can help.
J.H.: I cannot agree that the plain composition gasket causes pre-ignition-it was used on 10,000 engines
(650 and 750) before the 1st Commando and gave no trouble; part no. 25324 on the 6.50 and 25318 on
the 750. It came in with the spigotless cylinder barrel on the 650 and 750 at engine no. 114870, and the
lst Commando was 126125.»
Cylinder heads exist in an even greater variety. There are as standard, 30mm, 32mm, and tapered 30-
32mm inlet ports, three different chamber depths, varying in stages of 0.020in from the gasket face, for
the 750 and at least two for the 850, and I'm not counting the 750 short-stroke head which only fits on the
850 barrel and is only around in small numbers. Someday, someone will issue a chart of all the heads,
gaskets and pistons you can use and what compression they will produce, but it's not going to be me! The
only real way to find what you've got is to use a burette in the traditional manner.
The threads in the heads are, in general, BSF and Whitworth, and the exhaust ports are 1 15/16th x 14
tpi.
CHANGE IN COMPRESSION RATIO
With reference to four different cylinder heads and three head gaskets that have been in use on
Commandos.
All numbers are compression ratios: l. Figures in brackets are compression ratios with base gasket
removed. Loctite plastic gasket being used instead.
HEADS GASKETS
Part No. Types Port Dia. Compo 30thou 1mm Cu 2mm AI
060988 STD 1968/72 30mm 8.9 (9.2) 8.7 (9.0) 8.1 (8.3)
063327 'Combat' 1972 32mm 9.7 (10) 9.5 (9.8) 8.7 (9.0)
064048 STD 1972/73 32mm 8.9 (9.2) 8.7 (9.0) 8.1 (8.3)
064097 STD 1972/73 32mm 9.3 (9.6) 9.1 (9.4) 8.5 (8,6)
7

VALVE GUIDES: Everyone should know that the inlet valve guide must have an oil seal to help reduce oil
consumption. The 750 guides are too thin and when fitted right, collapse inwards slightly and give a belt-mouthed
condition from new. That's why the 850 guides are so much thicker, and they are also ground on the outside to give
good finish and concentricity (Hence the circlip, instead of a flange). If. a 750 guide works loose and facilities
permit, bore out to the 850 size and use the larger guides if you can get them. Some dealers sell bronze guides for
750's and 850's; the best material is hiduminium aluminum bronze Phosphor bronze in better than cast iron for
conductivity and coefficient of expansion, but worse for wear.
VALVES: The latest valves are stellited at the end (V263, V264), yes, both of them but they're not identified
because it's difficult to roll a number on satellite. Earlier valves have the part number on, but beware -- pattern
valves also have no numbers. The latest bits should be in a box, in pairs, but of course, they could run out of boxes
…
All I date say about valve spring seals and insulating washers is-leave them as they are, to suit the head you've got.
Many combat engines were made with cog-bound valve 'springs, and this was cured (bodged?) by omitting the
insulating washers from the inlet valves, which don't get so hot and sometimes grinding the valve spring seats
thinner to get a minimum of 0.050in movement of the valve at full lift. Not so critical with the standard cam, which
has less lift. but if you're not sure check before you run the engine-you can check with the engine in the frame, if
you must, by making sure that on full lift for each valve there is still fifty thou of lift available. (f there isn't, you'll
have cam wear, bent pushrods and broken valve springs, depending on how bad it is. Apart from this instance, the
only thing that breaks valve springs is not having the right ones.
PUSHRODS: Pushrod ends occasionally come loose, but will run happily like this for a While-but keep your eye on
the rocker adjustment. (To retain loose pushrod ends lightly centre pop the ally, then with a dob o/ Locktite gently
tap end cap back.) For those who insist on using planed heads, or combat heads, without compression plates, the
pushrods should be shortened to restore rocker geometry. Take as much off the pushrods as you did off the standard
head, and remember that Combat heads (marked C on top) have 0.040in planed off already, but that the factory
"forgot" to alter the rods, when the combat design was finalized. Rods are shortened by pulling one end off (easier
after having rods in the freezer first) and removing the desired amount of alloy from the middle bit. The cam
followers have a brazed-on stellite foot and should be bevelled on both sides to let the oil by. Check new ones, to be
sure they're not still full of casting sand. The Domiracer had thinner followers, with the pushrods going to the
bottom-much lighter, and worth a thought for racing. If you fit a different cam, be sure it doesn't foul the cam-
follower locating plates, and if you have the base circle ground, check that the plates allow the followers to fall far
enough, 750s only.
It is possible incidentally. to remove the head and barrel from any Commando as an assembly and the pushrods
should stay in place, so it's possible to Woe the head and barrel inside so you can locate the pushrods in the com
fort of the sitting-room and take the assembly out in the rain to fit it. But not on the 850s.
ROCKERS: The rockers can be lightened a bit, but not much, and it's useful to check that the valve end strikes the
valve centrally (some don't) - the arm can be bent slightly to give this condition. The adjusters are 9/32in BSF x 26
tpi, so one flat of ;he squared adjuster is almost exactly 0. in case you can't afford a set of feeler gauges. In spite of
the English thread sizes, some bikes have }in A.F. instead of 3/16in Whit hexagons for the adjusters, so watch
8