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…

Real Classic - - Back Issues - Pho­tos by Martin Pea­cock

My Com­mando was now a col­lec­tion of parts loosely bound by op­ti­mism. The pro­ject was at its low­est ebb, a more or less or­gan­ised col­lec­tion of crates and boxes of bits. In a state of max­i­mum en­tropy as Prof Brian Cox might say. It would take en­ergy, en­thu­si­asm and no small amount of cash to as­sem­ble those parts into a func­tion­ing mo­tor­cy­cle. Per­haps this is the rea­son some projects fail at this point, where progress, if it is to be made at all, stretches into the dis­tance, up­hill.

Re­solve and en­thu­si­asm alone were not enough, this re­quired a plan and I had one. Even as I was mer­rily tak­ing the bike apart, I printed off parts lists and di­a­grams and high­lighted them with red for parts needed and green for those I could re­use. There was an aw­ful lot of red on those sheets as I slot­ted them into a bin­der. This had tabbed sec­tions for the main as­sem­blies, di­a­grams and pages from the work­shop man­ual and, later, my notes, sketches and check­lists. Tech­ni­cal data went in the front, headed by my pro­ject out­line sheets and cur­rent task list.

Over-egging it only slightly, I listed the parts needed by group in a spread­sheet. The sort­ing and fil­ter tools made it easy see what was needed as well as parts al­ready in hand to­gether with pric­ing and sup­plier in­for­ma­tion. So much for or­gan­i­sa­tion, now for the real work.

Ul­ti­mately, ev­ery­thing at­taches to the frame, so that was my start­ing point, to­gether with the swing­ing arm, en­gine mount­ings, stands, yokes and sundry brack­ets. I masked the head­stock, yokes, swing­ing arm and ob­vi­ous places where pow­der coat did not be­long. What I did not know, but soon

learned, was that there were other less ob­vi­ous, ar­eas need­ing to be clear of pow­der coat.

I came across a se­ries of prac­ti­cal guides to re­build­ing a Com­mando on www.oldbritts. com, in­clud­ing one for mask­ing parts be­fore pow­der coat­ing. This would have been even more help­ful had I found it ear­lier, but that’s why we have scrap­ers and Dremel tools.

The guide was very clear about not hav­ing pow­der coat­ing be­tween the crank­case and its mounts. This is be­cause pow­der coat­ing is thick, soft and creeps from un­der tight, bolted con­nec­tions. The loos­ened bolts then bear the brunt of the en­gine vi­bra­tions rather than trans­mit­ting them to the Iso­las­tic mounts re­sult­ing in oval bolt holes and, even­tu­ally, sheared bolts.

Paint also doesn’t be­long where a close fit or earth con­ti­nu­ity is re­quired. No doubt opin­ions vary, as opin­ions will, but I had no prob­lems with as­sem­bly, electrics or loos­en­ing bolts af­ter fol­low­ing the rec­om­men­da­tions. The guide also points out, un­kindly I thought, that blank­ing off the crit­i­cal ar­eas is eas­ier and quicker than re­mov­ing the pow­der coat af­ter­wards.

Turn­ing to the gear­box, I re­moved the quad­rant, se­lec­tor cam and neu­tral switch be­fore be­gin­ning the messy job of clean­ing the gear­box shell. On the plus side, the gears, se­lec­tor forks, bear­ings, bushes and kick­starter were in very good con­di­tion. All I needed were new seals and gas­kets, but I or­dered a new ‘Su­perblend’ layshaft bear­ing, sleeve gear bear­ing and layshaft bush just to be on the safe side.

Given the gen­eral state of the electrics, I was pleas­antly sur­prised to find the neu­tral switch worked. This does no more than light a lamp in the warn­ing light con­sole, so the un­wary rider can still en­gage the starter with the bike in gear. I toyed with the idea of adding it to the starter cir­cuit as an in­ter­lock, but not for long. There were enough po­ten­tial prob­lems in that area with­out adding more.

A quick risk as­sess­ment on the hazards of us­ing the do­mes­tic oven for heat­ing the gear­box shell led me to im­pro­vise a hot box. Com­pris­ing a Roses tin, camp­ing stove, min­eral wool in­su­la­tion and espresso ma­chine drain plate, it eas­ily pro­duced tem­per­a­tures up to 220°C, as mea­sured by my bar­be­cue meat probe. That was more than enough for me to sim­ply drop the new bear­ings into place.

Re­assem­bling the gear­box was rea­son­ably straight­for­ward, other than paus­ing to re­move and then re­fit the layshaft bear­ing the right way around. The se­lec­tor forks were a bit of a fid­dle, as was ad­just­ing the neu­tral switch. Back­ing off the de­tent plunger helped with ro­tat­ing the se­lec­tor cam for this as well as fit­ting the se­lec­tor forks and check­ing gear se­lec­tion. I was, how­ever, ir­ri­tated to find that the new seal ‘set’ did not in­clude the ratchet quad­rant and kick­start seals.

The man­ual made no men­tion of re­mov­ing the layshaft bush and I couldn’t find any­thing help­ful on the In­ter­net. Heat­ing was no use be­cause the steel shaft has a lower co­ef­fi­cient of ex­pan­sion than the bush. In the end, I used a mini hack­saw (the type where the blade pro­trudes from the han­dle so it can be used in a blind hole) to cut a cou­ple of slots in the bush. This re­lieved the com­pres­sion enough to pull the bush out with an im­pro­vised draw tool. Leav­ing its re­place­ment in the freezer for a while al­lowed it to be drifted in with a few sharp blows.

Re­mem­ber­ing to fit the knuckle pin roller first, held with a spot of grease, I fit­ted a new gas­ket on the in­ner gear­box cover with Wellseal on one side and grease on the other to sim­plify dis­as­sem­bly. Then it was a mat­ter of get­ting the main­shaft and layshaft lined up with their re­spec­tive bear­ings and bush so the in­ner cover with its kick­start shaft and pawl could be jug­gled into place. I tight­ened the main­shaft nut to a ner­vous 40-50 lb.ft be­fore fit­ting the clutch lever as­sem­bly, tak­ing care to align the lever with the ca­ble en­try point marked on the cover.

As­sem­bly of the gear se­lec­tor mech­a­nism on the outer cover needs pa­tience and pre­ci­sion, es­pe­cially with the re­turn spring and hair­pin pawl spring. The pawl spring is crit­i­cal for proper gear se­lec­tion – or any se­lec­tion at all if it is badly po­si­tioned. This is well de­scribed in the help­ful NOC Ser­vice Notes.

The lack of a gear lever to help with po­si­tion­ing the ratchet and check­ing gear se­lec­tion made fit­ting the outer cover dif­fi­cult. I cut a piece of 0.3” ID steel tube, slot­ted it at one end and drilled holes for a tommy bar in the other. This al­lowed it to be se­cured to the splined quad­rant shaft at the back of the in­ner cover with hose clips. I could then ro­tate the ratchet quad­rant with a tommy bar. Although I couldn’t achieve the happy, sym­met­ri­cal up and down gear se­lec­tion de­scribed in the Ser­vice Notes, I could select all four gears and neu­tral rea­son­ably eas­ily. Re­mem­ber­ing to tighten the de­tent plunger so it was fully home, I put a large ‘tick’ next to the gear­box re­build item on my pro­ject sheets.

Fit­ting the new, bonded Iso­las­tic as­sem­blies into their mounts was dou­bly dif­fi­cult with frozen fin­gers and cold elas­tomer. It took a few whacks with a mal­let to start the Iso­las­tic cores in the front and rear mount­ings re­spec­tively. This was fol­lowed by care­ful lev­er­ing around the rims and ad­di­tional per­sua­sion for the Iso­las­tics to slide into their re­spec­tive, well lu­bri­cated mounts. From there it was a mat­ter of adding the end caps, thrust wash­ers, abut­ments and gaiters. The main stand was easy to fit at this point and made for real progress lead­ing di­rectly to in­stalling the en­gine and gear­box.

I com­pleted the en­gine bot­tom end over­haul by bank trans­fer and col­lec­tion of the now sparkling en­gine from Richard Ne­gus. It had not needed too much work but he had re­placed the camshaft as we had dis­cussed, big end shells, tim­ing chain, ten­sioner and a few other bits and pieces in­clud­ing screws and studs. He also sup­plied a CD with his in­spec­tion re­port and pic­tures of the work. ‘ Thor­ough’ doesn’t be­gin to de­scribe it and I hope or two pic­tures here will show what I mean.

With noth­ing on the frame to get in the way, I opted to fit the en­gine and its mount­ings as an as­sem­bly, start­ing by at­tach­ing the crankcases to the Iso­las­tic mounts with a set of in­dul­gently ex­pen­sive stain­less steel bolts. The front ones were just fine but the rear ones were 1/8” short. This meant the in­serts in the ny­loc nuts did not en­gage on the threads and could loosen should there be any vi­bra­tion (ie. if the bike ac­tu­ally started and ran).

The sup­plier promised to send re­place­ments once a new batch with the cor­rect thread length was pro­duced. These could be re­placed in situ so I car­ried on and fit­ted the en­gine in the frame with the help of a friend with strong arms. We of­fered up the en­gine so the rear Iso­las­tic mount aligned with its lugs and al­lowed me to slide the new mount­ing stud though to se­cure it. The front mount was at­tached in the same fash­ion with its bolt. That done, I slot­ted in the gear­box and se­cured it with its top and bot­tom mount­ing bolts, not for­get­ting the spacer for the top mount­ing lug.

Oil Tank Trou­bles

The large patch of epoxy on the bot­tom of the oil tank was not a good sign, and nei­ther was the un­tidy braz­ing around the re­mains of the orig­i­nal threaded mount­ing un­derneath. The only good news was that the tank did not leak, even with the epoxy re­moved. Nonethe­less, the bot­tom mount needed restor­ing to the state Nor­ton in­tended.

I thought about this over the course of fit­ting the rear mud­guard bracket to­gether with the bat­tery tray, rec­ti­fier and left panel brack­ets. Fit­ting a new steer­ing lock pro­vided one of those ‘ping – sod­dit’ mo­ments with the roll pin but I man­aged to find it and get that job done.

You may think that my as­sem­bly se­quence was a bit ran­dom, and you would be right. I have de­scribed the re­build in log­i­cal stages, but the same day could see me work­ing on el­e­ments such as the wiring, clocks, sus­pen­sion and pos­si­bly a dif­fer­ent bike al­to­gether. It was a mat­ter of main­tain­ing mo­men­tum as well as keep­ing the other plates spin­ning. Ex­cept where the as­sem­bly se­quence was im­por­tant, if I was held up by one task or just needed to think, I switched to another. My spread­sheet, notes and task lists were very help­ful, if not vi­tal, for keep­ing track un­der these cir­cum­stances.

My oil tank re­pair in­volved cut­ting a steel patch plate to fit over the dam­aged area to avoid dis­turb­ing the braz­ing that at least kept the oil in. A friend let me use his lathe to make a threaded boss to re­place the orig­i­nal and Flavell’s of Thorn­aby did a fine job of weld­ing the plate and new bot­tom mount in place. All that re­mained was for me to add a cou­ple of coats of paint.

Me­ta­las­tic mounts are not con­fined to the en­gine. Two bob­bin type mounts, at­tached fore and aft at the top, se­cure the oil tank. The bot­tom is fixed to the bat­tery tray by a ¼” UNF hex screw. This is dif­fi­cult to fit and can cause crack­ing around the bot­tom mount if one or both top mounts break, and break they do. The re­sult is the sort of com­pound bodge of braz­ing, epoxy and duct tape en­coun­tered with this one.

Given that it is se­cured by its top mounts, the job of the screw is to lo­cate the tank bot­tom on a grom­met in the bat­tery tray to stop the tank flap­ping about. A simple peg could do that, so I threaded a piece of ¼” rod and screwed it into the new bot­tom mount be­fore fit­ting the tank. The peg made this a lit­tle more dif­fi­cult, but it lo­cated in the grom­met as in­tended, pre­vent­ing lat­eral move­ment while al­low­ing some ver­ti­cal flex­ing of the top mounts.

Fit­ting the oil fil­ter, new oil lines and their newly painted flex­i­ble steel sheaths was sim­pli­fied by the ab­sence of rear mud­guard, swing­ing arm and main stand. Another task com­plete and checked off in the pro­ject file.

A Two Carb Prob­lem

Twin car­bu­ret­tors seem an un­nec­es­sary com­pli­ca­tion, at least in the con­text of clas­sic mo­tor­cy­cling. The ex­tra top end per­for­mance hardly seems worth hav­ing a poorer re­sponse at low rpm and the pain of get­ting the carbs tuned and syn­chro­nised. My Tiger 650 works very well with its sin­gle car­bu­ret­tor so why not the Nor­ton?

To say I ag­o­nised over this would be to over­state it, but I had a lot of trou­ble mak­ing up my mind. Go­ing to a sin­gle carb would cost more, mainly be­cause of the need for a two-into-one man­i­fold, but not enough to be a de­cid­ing fac­tor. Also, I had planned to use the orig­i­nal air­box as it car­ried the top at­tach­ment bracket for the left panel. The air­box could be mod­i­fied for a sin­gle carb though and I went as far as to start mak­ing an adap­tor plate for this.

Seek­ing ad­vice from a higher plane, I asked Richard Ne­gus for his thoughts. His re­ply, typ­i­cally to the point: was that the air­box was too re­stric­tive and only there be­cause of tighter US noise reg­u­la­tions. He rec­om­mended a K&N fil­ter specif­i­cally in­tended for the Com­mando twin carb setup. De­ci­sion made: I would per­se­vere with the orig­i­nal twin car­bu­ret­tors but ditch the air­box. I am still not sure this was the best de­ci­sion, but I sub­se­quently learned a great deal about set­ting up a pair of Amal Con­centrics.

There was no go­ing back. The air­box could not be fit­ted once the bar­rel, oil tank and bat­tery were in place. For­tu­nately, RGM were happy for me to re­turn the new fil­ter and other parts I had bought to re­place those miss­ing from the air­box. That done, I set the carbs aside for another day, a much later day as it turned out.

Fun With Forks

Now for the fa­mous, if by 1975, dated, Road­holder forks. More new ter­ri­tory for me but, with guid­ance from the work­shop man­ual and on-line ma­te­rial, the job of strip­ping and clean­ing them was no trou­ble. They were in very good con­di­tion and only needed new seals and gaiters, although I re­placed the rusted top nuts as well.

Even fit­ting the yokes was a snap thanks to the easy to fit, orig­i­nal sealed steer­ing head bear­ings. Fill­ing with fresh fork oil was tricky be­cause the damper rods and in­stru­ment pods take up most of the space at the top of the stan­chions. I used the rec­om­mended SAE-20 oil but have seen ATF rec­om­mended for an eas­ier fork ac­tion. All that re­mained for now was the fid­dly task of tight­en­ing the new top stan­chion nuts to the spec­i­fied 30 lb.ft while keep­ing the in­stru­ment pods in their cor­rect po­si­tions.

Rear Sus­pen­sion

I left the new swing­ing arm bushes soak­ing in oil for sev­eral days be­fore press­ing them into place with the new seals us­ing a vice with soft jaws. With its new spin­dle and bushes, the swing­ing arm was a tight fit. Not a bad thing, but it made lin­ing up the cot­ter pins dif­fi­cult. All be­ing well, it should bed in once we reached that still far away time of rack­ing up some road miles.

Those of you un­fa­mil­iar with the Com­mando may be sur­prised, as I was, by just how much load the rear en­gine mount car­ries. It doesn’t just hold the en­gine, pri­mary chain­case, gear­box, oil fil­ter and cen­tre stand, it also car­ries the swing­ing arm and, ef­fec­tively, the rear wheel. This is good prac­tise be­cause it puts the swing­ing arm pivot in close to the gear­box sprocket to min­imise changes in the chain ten­sion with

sus­pen­sion move­ment. It also en­sures the sprocket align­ment isn’t dis­turbed by flex­ing of the Iso­las­tic mounts.

On the down side, the en­gine mountcum-sub­frame adds con­sid­er­ably to the oth­er­wise light 24lb frame, putting it nearer to the Feath­erbed’s 34lb. More se­ri­ously, any slop in the Iso­las­tic mount­ings will cause some in­ter­est­ing han­dling as the swing­ing arm explores the re­sult­ing lat­eral free­dom. Cor­rect ad­just­ment of the Iso­las­tic mounts to min­imise lat­eral move­ment and reg­u­lar checks on the many and var­i­ous nuts and bolts is es­sen­tial.

Lu­bri­ca­tion for the swing­ing arm bushes re­lies on oil-soaked wicks at the ends of the spin­dle. That’s it! Sealed for life as they say. But how long is that? Copy­ing the well-tried ar­range­ment for AMC heavy­weights and ear­lier Com­man­dos, I drilled and tapped a hole in the right-hand Welch plug and sealed it with an old fork leg drain screw. This would al­low the ad­di­tion of oil from time to time. A cor­re­spond­ing hole through the right spin­dle wick al­lows oil through to the left side. I sealed the Welch plug it­self in place with sil­i­cone rub­ber rather than the in­tended thump with a drift. Only time will tell if this proves ef­fec­tive.

Bolt­ing on new NJB rear sus­pen­sion units fin­ished the job, although I later found they were a lit­tle longer than spec­i­fied and, if any­thing, I needed shorter ones. No prob­lem, an un­der­stand­ing Nor­man Blake­more was happy to make up a shorter pair, as a straight swap for the stan­dard ones.

Left: The Com­mando pro­ject folder, my se­cu­rity blan­ket!Be­low: The Com­mando frame is well de­signed and light, prob­a­bly half the weight of an AMC heavy­weight frame and 10lb less than a Feath­erbed. 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

Left: Rear en­gine mount: re­mov­ing pow­der coat from crit­i­cal ar­eas. The fi­nal step was to ap­ply a thin coat of paint to pro­tect the bare metal. This is a vi­tal com­po­nent car­ry­ing as it does the gear­box, crank­case, rear sus­pen­sion, cen­tre­stand and, ef­fec­tively, the rear wheel

Right: Mask­ing wash­ers for the Iso­las­tic are still in place. The fi­nal step was to ap­ply a thin coat of paint to pro­tect the bare metal

Right: The essence of a Com­mando, in­ge­nious and rea­son­ably ef­fec­tive solution to tam­ing the vi­bra­tions of a su­per­sized late 40s en­gine. Even so, it could only buy some time to de­sign and build a mod­ern mo­tor­cy­cle. Not enough time as it turned out

Left: Just keep adding bits un­til all the crates are empty…

Note the nar­row lig­a­ment be­tween the bear­ings, this can crack with hard use or ham handed bear­ing fit­ting. The in­ner race of the smaller, layshaft bear­ing is flanged and should pull out to be fit­ted on the end of the layshaft. In this case, the in­ner race flange is at the back of the bear­ing and re­quires a sec­ond visit to my hotbox

Cam­plate and quad­rant fit­ted. Look­ing good, no wear ev­i­dent

New big end shells fit­ted and the crankshaft halves bolted to­gether

A ‘Wolver­hamp­ton’ cam start­ing to wear. Ser­vice­able but prob­a­bly not for long

Crankshaft halves in ex­cel­lent con­di­tion

Just clean them up and put them back

En­gine and gear­box in­stalled. You can see the po­ten­tial al­ready

If the kick­start starts ro­tat­ing on its own with the en­gine run­ning, this bush (and pos­si­bly more parts) need re­plac­ing

Outer cover with temp gear lever fit­ted. Note the neu­tral switch be­low the im­pro­vised gear shift

Re­built en­gine bot­tom end. Richard Ne­gus works fast; I was still tak­ing the bike apart at this point

Oil pump and new tim­ing chain and ten­sioner

Re­assem­bling the crankcases and crankshaft

Cogs back in the box. Get­ting the hang of this gear­box as­sem­bly stuff…

The forked clutch arm must align with the clutch ca­ble en­try point

Main stand fit­ted. The de­sign al­lows the spring to be fit­ted first so you can use the stand legs as levers to line up the mount­ing holes and fit the bolts

Fit­ting the steer­ing head bear­ings. The red plate is the re­place­ment cer­ti­fi­ca­tion plate car­ry­ing the ma­chine (en­gine) num­ber and date, care­fully stamped by me. It is not much more than dec­o­ra­tion as the DVLA go by the frame num­ber. This wouldn’t mat­ter if HM Cus­toms hadn’t logged the ma­chine num­ber on their NOVA im­port cer­tifi­cate rather than the frame num­ber

Forks stripped. Just need a good clean and re­assem­bly with new seals, gas­kets and so forth

Forks re­fur­bished. Oh those gaiters again … but another task com­pleted

Sen­si­ble, sealed ball bear­ings mean no faffing about with in­di­vid­ual balls spilling out of their tracks as you try to fit the yokes. Noth­ing to ad­just ei­ther

Above: Orig­i­nal air­box with part-fin­ished adapter plate for sin­gle car­bu­ret­tor use. This was aban­doned in favour of re­tain­ing twin carbs with a free flow­ing K&N air fil­ter

Left: Note the mount­ing lug for the brake cal­liper on the left fork slider. This change, from be­hind the right fork leg, was to cure the prob­lem of the ear­lier 850’s pulling to the right even when the brake wasn’t be­ing usedBe­low: Swing­ing arm and new parts. Another weighty ob­ject … but it prob­a­bly needs to be!

The mod­i­fied Welch plug. Very dif­fi­cult to ac­cess once the Z plate and rear brake mas­ter cylin­der are fit­ted. This may be why Nor­ton opted for the oil soaked felt to keep the swing­ing arm lu­bri­cated. Note the oil fil­ter tucked in un­der the swing­ing arm mount

Left: Swing­ing arm fit­ted. Note the rub­ber plugs to keep the weather out of the cot­ter pin tun­nels. They worked, too

The story so far. Oil tank and shocks fit­ted, along with the in­stru­ment pods. Note the rear frame loop and the com­plete lack of sup­port or brac­ing. This needs to be borne in mind be­fore fit­ting a rack or pan­niers

Oil tank re­pair plate and boss. A fine piece of metal bash­ing and turn­ing, even if I do say so my­self

One oil tank bodge. Could have been worse, he might have used chew­ing gum…

Oil tank patch welded in place. Much less than a new tank

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