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- 850 Mk 1 1974
- Service Notes
Norton 850 Mk 1 1974 Service Notes
Summary of 850 Mk 1 1974
Page 1
Commando service notes complete with electric start text - tim stevens, john hudson editor -- alan osborn.
Page 2
One of the most popular, the 750 interstate 1973, with combat engine, signified by black barrels. Photo credit: motor cycle.
Page 3
Contents introduction and spares officers 2 engine numbers-model changes 3 group 1 :-- crank assembly including pistons, camshaft and timing gear. 4 group 2:-- barrels, gaskets and head parts. 7 group 3: -- timing cover, all therein and rocker feed. 10 group 4:-- crankcases, breathing and main beari...
Page 4
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 magaz...
Page 5
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)....
Page 6
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 scratch...
Page 7
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 pu...
Page 8
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 po...
Page 9
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, caus...
Page 10
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 als...
Page 11
It, (a.F, stands far american fred, by the way, a fact first mentioned in the vincent owners magazine.) (i thought it stood for awkward f----r!) rocker spindles: the rocker spindles are fitted with the oil flats outwards -away from the holes in the rockers --because otherwise too much oil swamps the...
Page 12
Group 3:- timing cover, all therein and rocker feed timing cover: not a part that's been messed about with much by the designer chappies. If you ever need a new one don't forget the oilway plug on the feed to the pressure release valve and of course the two oil seals. The middle seal (crankshaft) go...
Page 13
Screws which have 4ba spanner size but the right 2ba threads (b.S.A. Number 40.0683 ==triumph e7680) being smaller you might remember not to heave so hard. Finally the points cover has a little hole which is to let oil/water out and therefore goes at the bottom. Boyer or rita electronic ignition cur...
Page 14
To use the later black plastic type. White plastic examples were used on the production racers; they are equally good. Watch out incidentally for dunstall banjo bolts which have a restrictor to prevent over oiling- used in the days before inlet guide oil seals to reduce oil consumption. Remember tha...
Page 15
Group 4:- crankcases, breathing and main bearings crankcases: in comparison with the fairly clever design of the norton head, the crankcases are well, not to put too blunt a point on it, unsophisticated. It has been said that they only serve to keep the oil in and they're not very good at that! Anyo...
Page 16
Any norton, or any other proper motorcycle, you will have to write out 100 times, "this is the twentieth century"). As well as salt water getting into stud threads, gunk is another culprit; regular gunk cleans all the oil and grease away so eventually they'll get water in and seize, barrel studs bei...
Page 17
Groups 5, 6, 7:- gearbox the gearbox: this area is, i suppose, that with the most history behind it-for a start it is generally referred to as the amc gearbox as it was introduced when nortons were fairly new to the amc empire and shortly afterwards it found -its way onto the ajs and matchless heavy...
Page 18
The primary case (or file or even clip it away with tinsnips to about half the radial thickness). J.H.: i believe layshaft bail bearing failures arc more frequent when:- 1. The 22t gearbox sprocket is used as on 850s and 2. Every failure i have seen has been a portuguese skf bearing. In birmingham t...
Page 19
Smooth; finish with a stone or emery. After a while the ball gets flats on it they are very cheap, so polish the operating lever and a new ball, and a nylon lined cable and you should have the clutch the envy of others (except vincent owners). There are pattern kickstarts about with the top retained...
Page 20
Group 8:- primary case and clutch primary case: there is a commonly held opinion that all commando primary chain cases leak oil. In many cases, oil drops from the lowest part of the case--just where the joint is. Sometimes this oil collects from the rear chain --oil flings from the chain onto the ca...
Page 21
3. The rotor can seize in the stator and twist the end of the crankshaft. Then the tapers have got to be good. The woodruff key gets cut in half, if you are lucky. 4. The whole lot can seize and go round with the motor, taking the studs out of the back of the primary chain case. (so if you see your ...
Page 22
Appeared, read on. The drum itself is made of case-hardened steel, and with many more splines than the centre so there is no tendency for the plain steel plates to notch into the drum the innermost friction surface on early clutches was a separate steel plate located by two tiny little roll-pins in ...
Page 23
Group 9:- carburetors carburettors: the carbs themselves are the traditional amal deal: they work quite well but don't last very long-the slides rattle about in the bodies, a fault exaggerated by the fact that the engine shakes about anyway. Viton (synthetic rubber) tipped needles with brass bodies ...
Page 24
Group 10:- engine mountings engine mountings: this is the part of the bike which sets the commando apart from other machines, for although rubber engine mounts are used in all cars and bikes made by bmw, sunbeam, suzuki, mz, villiers and many others, nobody else had gone to such lengths to ensure th...
Page 25
Grease (not ordinary grease-as it will attack the rubbers and cause them to swell, although i know of riders who use ordinary grease and it does not seem to do much harm. A fairly thin sticky grease is best. Vaseline a not a good lubricant (not in this context anyway). Then surround the lot with one...
Page 26
Group 11:- frame, swinging arm and suspension frame: now all is to be revealed: the green eyed monster which appeared at the 1967 show had a frame with a tubular spine like all commandos since, but without the smaller horizontal tube below it. Instead it had a gusset plate wrapped round between the ...
Page 27
Wm3 rim as per dunlop recommendations: this gives a greater road tread contact area. Correct shimming is essential. Rear springs are 126lb standard wear, 150lb springs have hertz known to improve matters weight should he kept as for forward as possible by living low or flat bars; a tank top hag or s...
Page 28
(with a ‘71 or later machine on its centre stand you could take out the front bolt on the machine itself as there is practically no weight on it so long as the head steady has not been removed). Screw this into the end of the spindle. The first modification on mk 11a 850s whilst it retained the stup...
Page 29
Group 12:- footrest plates footrest plates: the most over-engineered part of the machine-not that there is much competition for the honor. They are forged from aluminum alloy and are unbreakable, even if the plates arc bent until one end touches the other they will not break. For concours rebuilders...
Page 30
Group 13:- the oil tank the oil tank is not over engineered. The mounting rubbers fail regularly because: 1. They are under strain due to the mudguard fouling the hoses and connections. 2. They are rot oil proof. 3. They are usually fitted twisted. If they are left broken the oil tank can't fall out...
Page 31
Groups 14, 15 and 16:- forks and front wheel, including front brake forks and front wheel,: the norton roadholder front fork achieved an enviable reputation in the early days of telescopic forks, due to a certain extent to a better clamping of the wheel spindle than some competitive designs, especia...
Page 32
Locking ring will unscrew if the rotation of the wheel is reversed. Do it by all means, but make up some way of securely locking the bearing ring. There isn't much that can be done to prevent the inside pad wearing rapidly in wet weather. The factory did make a scraper effort to fit beneath the cali...
Page 33
Group 18:- handlebar controls there are many variations in these bits and pieces which may not be obvious to the naked thingy: the brake and clutch levers: started off with good old fashioned steel levers-but there are also two types of the later lucas pattern. Early alloy levers were almost flat on...
Page 34
Groups 19, 21-24, and 28:- handlebars, side panels, front mudguard, seats, rear mudguard, tank and instruments all straight forward, no comments. Group 20:- exhaust systems not much to say about exhaust systems-i have already had a go about port threads. Don't use mutes in the straight through silen...
Page 35
Commando service notes- mk iii addendum these additional notes cover all models and the mk iii and have been put together by me from the experiences of the club members, so are perhaps not as exhaustive or full as the previous notes written by trs. Some more facts on the ss camshaft have come to lig...
Page 36
Engine main bearings: what again i hear you groan? A small point, quite often with the super-blend, the inner race, especially on the timing side, comes loose on the crankshaft; this does not seem to be detrimental in any way, so do not worry about it. The next time things are apart down there a blo...
Page 37
Slightly larger mean radius. This may increase wear marginally but in any case the bronze plates wear immeasurably so the life will now drop to only a few million miles ... My fiber clutch plates have dune 100,000 miles and are not noticeably worn. Thick oil and antifriction additives promote clutch...
Page 38
Sprag clutch inside engine sprocket and boss on large drive gear surfaces could do with fine emery (all emerys are fine! A spare joke) or "wet 'n dry" grade 600 to break up polish and give some grip. Starter sprag unit. Problems encountered by tine member are that this unit will function for weeks o...
Page 39
The pawl spring: this is the first item to suspect if you attempt to change gear and the lever has no effect or apparent connection into the box. The spring quite often wears and breaks (carry a spare one) and when you replace it with a new one you will more than likely have it) 'set' the spring as ...
Page 40
Go-faster mods, silencers and airboxes as previously mentioned the black cap annular discharge silencers do not significantly reduce power, but they must be kept with the balanced exhaust pipes. If you want to fit earlier separate pipes then you must fit the earlier reverse cone silencers. The rever...
Page 41
Isolastics: the front mk iii units can he fitted to any/all of the earlier models but the centre tube has to be shortened so that both ends are the same length, preferably by machining (as opposed to hack saw) to keep the ends square. The rear mk iii unit is not really worth the effort and expense o...
Page 42
Some tuning tips from c. Braddick "doubles" camshaft: this was definitely the most troublesome cam produced but probably the most powerful on sale to tile public. The problem associated with it were: - 1. Overlap-this was so large that with the lightest over-revving (missed gear usually the.Cause) t...
Page 43
Carburettors: t he twin carb tuning does not go far enough! To ensure both sides lift together at precisely the same time use a mirror placed against the air filter, in place of the rubber unions. L hen by looking back from near the handlebars you can clearly see the sides. Yet another way to ensure...
Page 44
Carburation the technical advice' questions on carburetion, at times, seem endless, along with the strange ideas some people have on the subject. A few basic facts, based on the mk i concentric; the main jet size is not that important and does not wear out! It starts to have an effect from 90mph plu...
Page 45
Oil further note, and explanations to the notes on page 28. When the norton twin cylinder engine came about in 1949 we had monograde oils only, therefore the design took this into account. The oil lubricated the parts and helped with the cooling, especially the cylinder head. The dirt from combustio...
Page 46
Keep polishing 44.
Page 47
The roadster again fitted with combat motor. Interesting to compare this with the type of 1970. (page 23). Photo credit: motor cycle. 45.
Page 48
Published by the norton owners club and printed by brazier & naish ltd. 202-204 high road, benflect essex ss7 5ld..