NORTON COM­MANDO Mk3 RE­BUILD

Real Classic - - What Lies Within -

Martin Pea­cock had a vi­sion, a con­ver­sion on the road to Bude. He un­der­stood that he wanted a Com­mando, and this is how he made it...

Iblame that chap West­worth for this. Even though Norton’s Com­mando has im­pressed me since see­ing a shiny green Fast­back pop an un­ex­pected wheelie in the late 60s, I couldn’t see my­self own­ing one. Just a lit­tle too much bike to han­dle and a rep­u­ta­tion for trou­ble. No, my ex­cel­lent 650 Tri­umph will do just fine thank you very much. At least that was my think­ing un­til I saw Frank’s im­mac­u­late Mk3, Elec­tric Start 850 gleam­ing in the Cor­nish sun­shine.

It looked gor­geous. Say what you like about the Com­mando, they re­ally got that part right, and there’s no harm in look­ing, is there? My mis­take was to take up the of­fer of a ride, a slip­pery slope if ever there was one. Start­ing on the but­ton, then a brisk run around the lo­cal lanes left me smit­ten by the strong en­gine, com­fort, easy han­dling, real brakes and, well the whole pack­age.

Smit­ten or not, I was aware of the ups and downs of own­ing a bike wag­gishly but not in­ac­cu­rately de­scribed as: ‘a bril­liant but deeply flawed mo­tor­cy­cle.’ This had less to do with bad de­sign than se­nior man­age­ment be­ing more con­cerned with in­ter-com­pany ri­val­ries and set­tling old scores than mak­ing a world beat­ing mo­tor­cy­cle. Norton’s engi­neers knew what was needed but had lim­ited scope to im­ple­ment changes. This sad tale is re­lated by Steve Wil­son in his book: ‘Norton Mo­tor Cy­cles from 1950 to 1986’. Tony Page in RC71 de­fined his Com­mando as the ul­ti­mate clas­sic bike: ‘...it has to do ev­ery­thing well and be the bike that I lust af­ter while gaz­ing at it in the sun­shine or rain de­spite al­ready own­ing it.’ Or as the Frank him­self puts it in RC76: ‘Some mo­tor­cy­cles just make a chap want to ride. To for­get the day to day non­sense of earn­ing a liv­ing, feed­ing the cat and so forth. This Com­mando is one of them.’

Yes, there is no short­age of praise and with up­graded parts it can be a mag­nif­i­cent ma­chine or, with less able or ne­glected

Martin Pea­cock had a vi­sion, a con­ver­sion on the road to Bude. He un­der­stood that he wanted a Com­mando, and this is how he made it…

span­ner work, a night­mare Nonethe­less, most Com­mando rid­ers love their bikes – in­clud­ing the owner of a Mk3 In­ter­state I met. He was still rid­ing his some 40 years and over 250,000 miles since buy­ing it new. This ap­peal goes far be­yond rea­son: if the Bon­neville is a 60s icon then the Com­mando is surely its younger mistress; and a high main­te­nance one at that.

I could hardly re­sist and started look­ing out for a de­cent Mk3. This was the fi­nal de­vel­op­ment, not just of the Com­mando but also Bert Hop­wood’s hastily penned 1948 de­sign for a mild man­nered 500cc twin. Now a rasp­ing 828cc, paired with a gear­box de­signed in 1953, it was a tes­ti­mony to Norton’s cash strapped engi­neers that they pro­duced such fine per­form­ing ma­chines well into the 70s.

By this time, the Com­mando had put on weight, tip­ping the scales at around 430lb (196kg). Though lighter than 500lb con­tem­po­raries like the T160, it had no more power than the svelte 750s. What it and the ear­lier 850s had, how­ever, was stump pulling mid-range torque from a low revving en­gine de­signed to over­come the dam­ag­ing high pis­ton speeds and bot­tom end flex­ure of the 750 Com­bat en­gine. Still no slouch but more cruiser than su­per­bike, the Mk3 was in­tro­duced with around 140 changes from the pre­vi­ous model. These were to im­prove re­li­a­bil­ity, meet tougher US reg­u­la­tions and com­pete with the lat­est Ja­panese of­fer­ings:

Elec­tric start, marginally ef­fec­tive but it can work well with up­graded parts New switchgear Rear disc brake Left foot gear change Hy­draulic pri­mary chain ten­sioner Large but re­stric­tive air­box to re­duce noise Im­proved, sprung head steady Hinged seat Anti-sump­ing valve and screwed plug for tim­ing chain checks Strength­ened crankcases with larger di­am­e­ter crank­case bolts and shot peened con­rods ‘Vernier’ Iso­las­tic mounts (ad­just­ment by a threaded end cap in­stead of shims)

Even­tu­ally I spot­ted a re­cent USA im­port that seemed a good prospect for my very own ul­ti­mate clas­sic bike. It was de­scribed with more en­thu­si­asm than ac­cu­racy but on the face of it there wasn’t any­thing ma­jor needed to get it up to scratch. The tim­ing and lo­ca­tion were con­ve­nient for the Stafford Show so I ar­ranged to see it. The trou­ble was that I didn’t know what I was look­ing for and didn’t have some­one who did with me. Such fool­ish­ness has a price and I over­looked many im­por­tant points such as the miss­ing front mas­ter cylin­der. Yes, I spot­ted it was miss­ing but did not know that a re­place­ment was prac­ti­cally un­ob­tain­able. Other miss­ing parts were the elec­tric start in­clud­ing the en­tire

starter train, side panel, coils, coil bracket and oil sep­a­ra­tor for the oil tank breather.

Later I found that some of the parts still at­tached were from early mod­els, such as the 750-type head steady, car­bu­ret­tors and man­i­fold stubs. These were the early 30mm types not the cor­rect 32mm. Richard Ne­gus spot­ted that and more from 120 miles away from a pic­ture I sent of the newly re­built bike, but I had missed that lit­tle de­tail com­pletely. On the plus side, it turned over, had good com­pres­sion, all four gears and had no signs of ac­ci­dent dam­age. Strangely, it had brand new tyres and plugs. No coils, con­tact breakers, bat­tery, ig­ni­tion wiring or key and only one HT lead, but new plugs. As an Amer­i­can might say: ‘Go fig­ure!’ At least the starter so­le­noid was there, but it didn’t work. I won­der what he meant by: ‘All electrics are cor­rect and in good or­der.’

Of course I bought it! My of­fer was clearly not low enough, such was the ea­ger­ness of its ac­cep­tance. Still, even at the price paid, a bud­get of £3k - £4k would put me in the right bracket for a good Mk3, wouldn’t it? Pause here for a wry smile…

Let’s talk about that, bud­get­ing for recom­mis­sion­ing, restora­tion, re­build­ing – call it what you will. There is the es­sen­tial stuff: miss­ing parts, worn out or corroded parts, seals, gas­kets, fas­ten­ers, tools and so forth. Much trick­ier though are de­ci­sions about re­plac­ing func­tional but corroded fas­ten­ers, re­fin­ish­ing chromed and painted parts and fit­ting new, up­graded parts for im­proved re­li­a­bil­ity and longevity. Ex­am­ples are elec­tronic ig­ni­tion (a no-brainer in the ab­sence of coils and con­tact breakers); a chill cast camshaft re­plac­ing the still ser­vice­able but gen­er­ally short lived case-hard­ened orig­i­nal, 3-phase al­ter­na­tor with solid state reg­u­la­tor and heavy duty AGM bat­tery.

All very sen­si­ble, but that was £525 out of the bud­get. Add a sur­pris­ing £310 for mostly stain­less nuts, bolts, screws and wash­ers; £750 for paint­ing, chrome plat­ing and pow­der coat­ing; £100 for spe­cial tools, £190 if you count the vac­uum gauges and op­ti­cal tachome­ter for set­ting up the car­bu­ret­tors and clocks. Don’t dis­count postage charges ei­ther with VAT on top: that lot came to a whop­ping £440. That’s over £2000 be­fore costs for the en­gine work, sus­pen­sion, gear­box, pri­mary drive, Iso­las­tic mounts, electrics, car­bu­ret­tors, brakes, wheels and, well, ev­ery­thing else. I put off buy­ing the elec­tric start components, espe­cially the up­graded mo­tor, as they are in a league of their own, but most parts are not all that costly. It’s just that there are an aw­ful lot of them.

I es­ti­mated that there are over 2100 parts that must fit and work to­gether. By the time I’d fin­ished, each and every one had been re­placed, re­paired, re­fur­bished or re­fin­ished – right down to the spokes. This is the ad­van­tage of ig­no­rance, you can get on with a worth­while project that you wouldn’t touch if you knew more up front.

Mean­while, back in the shed with the sorry look­ing Com­mando, it was time to get or­gan­ised. A bit late I know but I started with read­ing through the work­shop man­ual and NOC Ser­vice Notes to get an idea for how it should be put to­gether and, in­deed, taken apart. By now there was no doubt about that and, not to push the mistress anal­ogy too far, this called for a com­plete strip down.

The petrol tank was easy, with its sev­ered fuel lines and just a bungee cord hold­ing it on. The seat sim­ply lifted off af­ter slack­en­ing the knurled knobs – so much for the Mk3’s hinged seat! My bike lift and a cou­ple of ex­tra hands for the pushrods made re­mov­ing the head much eas­ier – apart from deal­ing with the near in­ac­ces­si­ble in­board car­bu­ret­tor Allen screws.

This re­vealed stan­dard, shiny topped pis­tons and bores that looked re­cently honed. The head wasn’t so good, with the left com­bus­tion cham­ber oily and black with car­bon de­posits. One valve guide was bro­ken and, as I found later, that wasn’t the worst of it… but at least it was the right head, although prob­a­bly not the orig­i­nal. Re­mov­ing the bar­rel con­firmed the pis­tons were orig­i­nal He­po­lite and the con­rods, camshaft and fly­wheels looked to be in good con­di­tion.

Re­mov­ing the pri­mary chain­case was straight­for­ward, although I was sur­prised to drain over two litres of clean en­gine oil be­fore re­mov­ing the outer cover. There was more in the crank­case but none in the ac­tual oil tank. All that re­mained of the starter train was the idler gear. This also re­vealed the neatly im­ple­mented gear change cross­over shaft, slightly an­gled back to the rear of the gear­box in­ner cover. The ar­range­ment in­cluded an idler gear on the gear lever shaft to re­verse the shift pat­tern to the ‘stan­dard’ up for up. Thus, the orig­i­nal Com­mando’s crisp ac­tion was sac­ri­ficed on the al­tar of uni­for­mity.

The gear­box had to be fixed in place for the cross­over shaft, so the clever chaps at Norton squeezed in a hy­draulic chain ten­sioner. This was a good ex­am­ple of an en­gi­neer­ing so­lu­tion to the chal­lenge of get­ting more life from those 20 year-old de­signs. Hap­pily, the triplex chain and sprock­ets were in good or­der as was the clutch, other than for hav­ing a mix­ture of bronze and com­po­si­tion plates. The al­ter­na­tor sta­tor looked cooked, but my first real chal­lenge was re­mov­ing the en­gine sprocket. This re­quired a puller, heat and nu­mer­ous blows to the side of the sprocket to free it.

An­other dif­fi­culty was re­mov­ing the in­ner cover, I even checked to see if I had missed a fas­tener or two. Even­tu­ally I ap­plied some ro­ta­tional force to shear what proved to be ‘Yam­abond’ sealant be­tween the chain­case and crank­case.

Fol­low­ing the man­ual, I re­moved the front Iso­las­tic mount and pro­ceeded to take out

the crank­case bolts to free the en­gine for re­moval. All well and good… but for the bot­tom bolt that ap­par­ently needed to come out through the right frame rail. Af­ter a bit of head scratch­ing, I re­alised that the en­gine mount piv­ots on the rear Iso­las­tic so it was a sim­ple mat­ter to lift the crank­case un­til the bolt head cleared the frame rail.

My plan was to dis­man­tle, in­spect and re­build the bot­tom end, some­thing I had never done be­fore. The bike only had 15,000 miles on the clock, but even if that were true, it had over 40 years on the cal­en­dar and time can do ter­ri­ble things to a ma­chine. For­tu­nately, a noted ex­pert in such mat­ters ad­vised ask­ing RC reg­u­lar Richard Ne­gus if he would take it on. He would, he did. Yes, this was an un­bud­geted ex­pense but who bet­ter to sort a Com­mando mo­tor than a man from the orig­i­nal de­vel­op­ment team? Quite apart from that, reg­u­lar read­ers will know very well that the cost of a novice re­build can be much more.

De­liv­er­ing the en­gine bot­tom end to Richard en­abled me to drop off some rusty parts, in­clud­ing the footrest hang­ers, brake pedal, kick­start and head­lamp, for rechroming by Pres­tige Elec­tro­plat­ing. The help­ful lady be­hind the desk re­marked that they had some sim­i­lar parts in be­fore. Yes, she agreed, from a Scot­tish fel­low, pos­si­bly named Urquhart…

Richard im­me­di­ately showed his ex­per­tise by re­mov­ing the tim­ing cover and spot­ting the lack of a spring and plunger that should stop oil drain­ing into the crank­case. I learned later that some bikes left the fac­tory that way. Other mi­nor is­sues in­clud­ing a worn tim­ing chain ten­sioner but the ‘Wolver­hamp­ton’ camshaft and its faulty case har­den­ing was a concern. Although it was still ser­vice­able, there were signs of wear and I only wanted to do this job once.

Re­plac­ing some parts be­fore their time added to the cost, but I was build­ing this mo­tor­cy­cle to ride, not end­lessly faff about with its in­ter­nals and run­ning gear. As I look back from over 2500 miles of trou­ble-free rid­ing, I can’t say I have re­gret­ted a sin­gle penny spent in this way.

There was noth­ing ob­vi­ously wrong with the head – with the em­pha­sis on ‘ob­vi­ous’ but Richard’s sharp eye spot­ted a clus­ter of cor­ro­sion pits in the bar­rel – ‘ That will smoke’, and a bro­ken fin (glued back on, but at least it was there). I left him with the bot­tom end to sort out. Once home, I bor­rowed a pit gauge and mea­sured the cor­ro­sion depth at be­tween 0.1 and 0.4mm so a +40 re­bore and over­sized pis­tons were added to my grow­ing list.

Turn­ing to the frame and run­ning gear, I re­moved the gear­box sprocket af­ter a strug­gle lock­ing the back wheel with­out a work­ing brake. The chain and sprock­ets were badly worn with ev­i­dence of the chain rub­bing on a lug on the swing­ing arm and frame rail, so that lot went on the dis­card pile. The wheels were no trou­ble to re­move, but the front rim and pos­si­bly the rear needed re­plac­ing. The discs and calipers were in

rea­son­able con­di­tion, so I kept them with the rear mas­ter cylin­der for re­fur­bish­ment.

Turn­ing to the switches and electrics, I found the han­dle­bar switch sub-har­nesses needed re­plac­ing: did I men­tion the seller de­scrib­ing the electrics as be­ing in good or­der? Thank­fully, the vir­tu­ally un­ob­tain­able switches worked but the main har­ness mul­ti­con­nec­tor shells were brit­tle although the main har­ness it­self could be re­tained.

The warn­ing light con­sole needed new lamps, de­cal and at­tach­ment bracket. Both the ig­ni­tion and steer­ing lock keys were miss­ing, as were the front in­di­ca­tors and speedome­ter in­ner cable. Check­ing the clocks with a vari­able speed drill and tacho cable showed the tachome­ter was work­ing as was the odome­ter but there was only a twitch or two from the speedome­ter nee­dle.

Chal­lenges to come were the swing­ing arm and rear Iso­las­tic mount, both seized, but the bat­tery car­rier, rear mud­guard, Gir­ling units, right Z-plate, stand, chain­guard and so forth were eas­ily re­moved. The swing­ing arm seizure was prob­a­bly an in­evitable con­se­quence of re­ly­ing on oil soaked fi­bre pads in­stalled over 40 years pre­vi­ously for lu­bri­ca­tion. Hap­pily, the cot­ter pins came out eas­ily. I then re­placed one to lock the spin­dle and used the other to plug the re­main­ing, bot­tom hole. This al­lowed me to fill the cen­tral area with Plus­gas to soak for a few days. Mov­ing the swing­ing arm a small amount grad­u­ally be­came eas­ier and I added more Plus­gas as it mi­grated along the spin­dle. Even­tu­ally I could draw the pivot spin­dle out us­ing the front Iso­las­tic mount­ing bolt.

Strip­ping down the gear­box filled the time while the pen­e­trat­ing oil was do­ing its job. Its in­ter­nals were in good con­di­tion, sug­gest­ing this was in­deed a low mileage ma­chine. The layshaft wouldn’t budge so I ap­plied a heat gun to the back of the gear­box un­til it pulled out com­plete with its bear­ing. Sim­i­larly, a few light taps re­leased the sleeve gear and its bear­ing.

Apart from the oil tank, sit­ting on an oily pad of rub­ber strips bound by duct tape, just the rear Iso­las­tic en­gine mount with its cap­tive right Z-plate and oil fil­ter re­mained of the back end. The oil tank was fid­dly to re­move but just left the stub­born rear Iso­las­tic stud. Heat, an im­pro­vised draw tool and vi­o­lence failed to make any im­pres­sion so I re­sorted to thought while car­ry­ing on with other, sim­pler tasks.

This, thought that is, be­came a fea­ture of this project. Step­ping back from a seem­ingly in­sur­mount­able prob­lem be­fore in­flict­ing dam­age or re­sort­ing to an ugly bodge. Fo­cus­ing on other tasks helped steer my thoughts from what should be to how things were and, im­por­tantly, how to solve the prob­lem. Some­times it would take a few days but, in­vari­ably, this would pro­duce the so­lu­tion and we would move on.

In this case, I rea­soned that the stud, pass­ing through the Iso­las­tic mount­ing was rusted in place. Rust is not an ad­he­sive but

iron ox­ide has four times the vol­ume of the steel it re­places. When you get that amount of ex­pan­sion in­side a close-fit­ting steel tube, there is no shift­ing it. Not­ing that the stud ro­tated freely in the frame lugs, all I needed to do was sep­a­rate its ends from the mid­dle – with a hack­saw.

Care­fully saw­ing in­board of the end wash­ers left the frame lugs safe, with dam­age lim­ited to the eas­ily re­placed thrust wash­ers and ad­juster. Once the ends were re­leased, the en­gine mount and Iso­las­tic core came out eas­ily, still hold­ing the re­mains of the stud in a death grip.

Thank­fully, re­mov­ing the front forks and yokes, wiring loom and re­main­ing few bits and pieces, in­clud­ing the mys­te­ri­ous ‘blue thing’, was straight­for­ward. Stripped bare, the frame was not a pretty sight, my idea of sim­ply touch­ing up the paint was clearly a non-starter. Not only would it be a right faff, espe­cially clean­ing off the pet­ri­fied duct tape, it would let down the rest of the re­build. Be­sides, there wouldn’t be a bet­ter op­por­tu­nity to paint it prop­erly or, in my case, go for the price and con­ve­nience of pow­der coat­ing al­ready planned for the an­cil­lary parts such as en­gine mounts and stands.

So, mind­ful of ‘spoil­ing the ship for a ha’p’orth of tar’, I punched an­other hole in my no­tional bud­get and duly re­moved the head­stock bear­ings and cer­ti­fi­ca­tion plate…

A good Com­mando is a won­der­ful thing and FW’s was ex­cel­lent. Do not ac­cept a ride on such a bike, it will surely turn your head

Left: ‘Orig­i­nal un­re­stored Com­mando that was last used 2 years ago in the States, me­chan­i­cally it is sound...’ At least its lo­ca­tion was true. Apart from that, it was not ‘orig­i­nal’ in the sense that it had its orig­i­nal or at least cor­rect parts, and much of it was un­sound

Apart from the right carb miss­ing its slide and nee­dle the carbs were in good con­di­tion. Ev­i­dently the ear­lier model 750 Com­mando they be­longed to hadn’t done many miles. Martin claims to have been clue­less; it took Richard Ne­gus to spot that. Note the thor­oughly choked pi­lot air holes

Noth­ing much wrong with the head steady other than it be­ing a much ear­lier type and not right for the Mk3

‘This bike could be recom­mis­sioned quite eas­ily as it is and used as a rider or re­stored to its for­mer glory.’ Yup, just ad­min­is­ter some snake oil and away you go

Head and bar­rel off, rear brake mas­ter cylin­der, wheels, rear lamp assem­bly, footrests and so forth. Good progress so far

A rear brake lock bodge. Disc brakes don’t work well with­out their hy­draulics. Clamp­ing wooden blocks on the disk was ef­fec­tive in al­low­ing loos­en­ing of the gear­box sprocket nut

Pos­si­bly the cor­rect mileage or some­where near. The miles rolled over when driven but hardly more than a flicker from the nee­dle

Note the splined gearchange shaft pro­trud­ing from the in­ner gear­box cover. This cou­ples to the cross­over shaft from the pri­mary chain­case. The im­mov­able rear mount stud and iso­las­tic mount can be seen in the back­ground

Head re­moved. Not look­ing too bad; note the oil in the com­bus­tion cham­ber

Apart from the bro­ken valve guide, the valve gear looks OK. New valve guides and re­cut seats should do it. In the event, weld build-up and ma­chin­ing was re­quired to re­store the al­loy bro­ken off be­hind one of the seats

Even though Martin had planned to fit elec­tronic ig­ni­tion, it was an­noy­ing to find some­one had al­ready nicked the points. The pis­tons and con­rods look good – pity about need­ing a re­bore to clear cor­ro­sion pits in the bar­rel

In­side the pri­mary drive. Dodgy look­ing sta­tor but oth­er­wise look­ing OK. Note the gearchange cross­over shaft with idler gear and chain ten­sioner be­tween the clutch and al­ter­na­tor

The clutch di­aphragm re­moval tool is es­sen­tial. This one was given to me by a friend and was orig­i­nally used in the Northaller­ton po­lice work­shop

Gear­box in­ter­nals in good con­di­tion. Need some heat to re­move the layshaft and its bear­ing

Rear iso­las­tic re­moved. Note the mount for the swing­ing arm pivot and hous­ings for the cot­ter pins

The back of the right hand switch block. There should be a brake mas­ter cylin­der at­tached. All we need do is find one to fit

The so­le­noid doesn’t work, the blue thing is a large value ca­pac­i­tor to al­low kick start­ing the bike when the bat­tery is flat and the se­le­nium rec­ti­fier can go the way of the Zener diodes – into the bin. A large ca­pac­ity bat­tery, 3-phase al­ter­na­tor and solid state reg­u­la­tor will re­place them

The Com­mando frame is well de­signed and light, prob­a­bly half the weight of an AMC heavy­weight frame. The prob­lem is that just about ev­ery­thing at­tached to it is heavy. Leav­ing the swing­ing arm bushes in place to mask the bush mount­ing holes was a mis­take. The pow­der coaters had a big prob­lem with oil sweat­ing out of the bronze bushes when hot. For­tu­nately they manged to over­come it

Rear mas­ter cylin­der a real mess but at least it was still there. Those Mec­cano si­lencer hang­ers are def­i­nitely not in the Norton parts list and we need some chroming done

Com­mando kit of parts. There should be a re­ally nice bike in there. Note the shiny bot­tom end. Richard Ne­gus was far more ef­fi­cient in strip­ping and re­build­ing the en­gine than Martin was in tak­ing the bike apart

Right: Warn­ing light con­sole. Should be Green, Am­ber, Blue and Red ... and ac­tu­ally con­nected to some­thing

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.