PUB popped down to Popham for their Mo­tor­cy­cle Megameet, in­stead of vis­it­ing Brack­ley’s Fes­ti­val of Mo­tor­cy­cling which was sched­uled for the same week­end. In the work­shop her ef­forts ex­pose some of the reper­cus­sions of grind­ing/lap­ping in of ta­pers…

Real Classic - - Contents -

PUB popped down to Popham for their Mo­tor­cy­cle Megameet. In the work­shop her ef­forts ex­pose some of the reper­cus­sions of grind­ing/lap­ping in of ta­pers…

The Bill Lacey meet­ing at Even­ley (Northamp­ton­shire) al­ways brings out a lot of in­ter­est­ing clas­sic ma­chin­ery, but PUB also no­ticed a mod­ern Chi­nese 125 ‘HPS’ (they wanted to call it Hip­ster, but that name is taken else­where). Read­ers may have read that the FB Mon­dial name is res­ur­rected again, and as PUB has one of the old Grand Prix Mon­di­als from their hey­day of win­ning World Cham­pi­onships (prior to the ma­jor Ital­ian fac­to­ries with­draw­ing from GP racing in 1957) this piqued her in­ter­est. The model is not an­other Yamaha YBR clone, but fea­tures a Pi­ag­gio de­signed dohc en­gine with the full fat 15bhp that learn­ers are per­mit­ted (claims vary be­tween 10 & 11kW), rather than the more com­mon 11bhp of the clones. Ap­par­ently the cur­rent Count Boselli is one of the team re­spon­si­ble for the re-in­tro­duc­tion of the name, of which the FB pre­fix stands for ‘Fratelli Boselli’.

Mis­take of the month came when B44 Clive men­tioned that he had to col­lect some parts from the same re­pairer to whom AJS Mary had sent her Rex-Acme en­gine and gear­box, it pro­vided an op­por­tu­nity for PUB to join him and col­lect it for her.

The box of parts con­tained a re­built Vil­liers en­gine and Al­bion gear­box, plus a sur­pris­ing ar­ray of var­i­ous rusty/oily bits. Some of these turned out to be items that had been re­placed (which was good), but others were items not touched (not so good). In the lat­ter cat­e­gory were the scruffy kick­start and spring, but more sig­nif­i­cantly the for­mer didn’t fit the very dis­tressed kick­start shaft. Ad­mit­tedly that was how it had been be­fore, but it wasn’t how PUB was pre­pared to re­assem­ble the bike. Ideally the shaft would have been prop­erly re­paired by metal spray­ing and ma­chin­ing back to stan­dard, but that would have meant dis­man­tling a very ex­pen­sive re­build, and spend­ing lots more. The shaft ought to be hard, but was no longer so due to for­mer own­ers’ machi­na­tions with welders etc. That be­ing the case PUB took her lead from Odgie, that much can be achieved with a welder and an­gle grinder – al­though she does not have Odgie’s skill with ei­ther.

Adding metal was a slow process as only a lit­tle weld could be ap­plied at a time be­fore it was nec­es­sary to cool the shaft down (with wet rags) to pre­vent any­thing in­side the box get­ting hot. As she is not very good, a few ex­tra spots had to be ap­plied later, when the cut­ting down process re­vealed dips or slag. Ac­tu­ally PUB does not use an an­gle grinder very much, be­ing a bit too likely to ac­ci­den­tally re­move too much metal, so more la­bo­ri­ously filed most of the ex­cess off.

Once the kick­start would go on to the shaft a small way it was pos­si­ble to see where it stuck (ei­ther by pol­ish marks, or en­gi­neer’s blue if re­quired) and slowly take off the high spots (lat­terly with a small Swiss file) un­til it went on with a snug fit. The kick­start was ex­pected to be held by a bi­cy­cle type cot­ter pin, with mat­ing flat on the shaft, how­ever pre­vi­ous owner ap­pears to have drilled straight through as part of their fix, leav­ing a semi-cir­cu­lar groove in­stead. For­tu­nately, the at­ten­tion to the shaft meant that this groove no longer quite lined up, so that a ta­pered pin

would tighten up in much the same way as the nor­mal ta­pered cot­ter. Knock­ing up and thread­ing a suit­able pin did not take long on the lathe. The re­fit­ted kick­start ap­pears to be sound enough, es­pe­cially as it only has to spin a vin­tage 250cc twostroke.

An ex­tra lit­tle job was to make a new clutch lever pivot pin. The re­builders had re­fit­ted the old one, which was quite ser­vice­able, but very sloppy. As nei­ther the lever nor the cast­ing has an ex­cess of metal, nei­ther was drilled/reamed over­size, but in­stead a new pin was turned and threaded to suit the worn di­am­e­ters. There is now much less slop and ‘lost mo­tion’, which is sat­is­fy­ing if not ter­ri­bly im­por­tant.

The en­gine, too, did not en­tirely meet PUB’s stan­dards, low as they might be (re-us­ing sound old parts and even bear­ings be­ing nor­mal). In par­tic­u­lar, the main­shaft ta­per was rough from cor­ro­sion al­though now blasted clean. Its mat­ing fly­wheel and sprocket re­mained in their dirty and un­fit­ted state – pos­si­bly be­cause the re­pair­ers had noted that the en­gine plate studs can­not be in­serted with both mag­neto and drive-side fly­wheels fit­ted. Mary had sent it to them with those studs and two of the four en­gine plates still in

place, which ex­plained why only two of the re­quired four en­gine plates were present. The ta­per could have been left for later, but there are fewer tools and fa­cil­i­ties at Mary’s place, so it seemed bet­ter to tackle it at home.

The only op­tion now (rather than whilst it was apart) was to lap in the ta­per. How­ever, there are snags with do­ing this, of­ten though it is rec­om­mended (usu­ally for mag­neto sprocket ta­pers). For a typ­i­cal ta­per, the sprocket align­ment will shift by 6 thous or so to take up 1 thous of ex­tra ta­per clear­ance. How­ever, one thous of ac­tual metal re­moval pro­duces 4 thous clear­ance (2 thous each side of the shaft and an­other 2 each side of the hole), and so po­ten­tially 24 thous mis­align­ment. Grind­ing in ta­pers should be done only as much as is nec­es­sary, es­pe­cially one as shal­low as this A se­ries Vil­liers looked.

Fur­ther­more the min­i­mal clear­ance be­tween fly­wheel boss and crank­case sug­gested that this would not be the first time for this en­gine, and that the boss would have to be cut back first, to gen­er­ate enough clear­ance to ac­com­mo­date the above ef­fect. The fly­wheel was too big to go in the lathe di­rectly, and mak­ing up a man­drel to mount it on too much trou­ble, so some more la­bo­ri­ous fil­ing re­duced the boss – its thread pro­vid­ing some guide to keep­ing things square. Next, and re­flect­ing the need to re­move the least metal, PUB used a small stone to clean up the shaft alone, since the sur­face in­side of the fly­wheel looked fairly good. Again the use of en­gi­neer’s blue kept this shaft ston­ing process from go­ing awry. Then some fine grind­ing paste was ap­plied, and the usual grind­ing-in process un­der­taken.

As soon as a rea­son­able con­tact area was vis­i­bly ob­tained, the process was stopped, with­out at­tempt­ing to get through all the cor­ro­sion pits – which would be too much metal re­moved. Even so, the

align­mentin ad­di­tion movedto any pre­vi­ousin ex­cess fig­ure.of 1/32 The inches, nicewell move­new cork­sthat sprock­etin the clutchthe other plates way may a sim­i­lar amount, so PUB can ex­pect any­thing up to 1/10 inch pri­mary drive mis­align­ment (de­pend­ing on how good it was pre­vi­ously). Hope­fully the en­gine plate ar­range­ment should al­low spacer read­just­ing if nec­es­sary.

How­ever, that is not the only reper­cus­sion of grind­ing in a ta­per. An­other is that the shaft will move fur­ther through the hole, and it may even fin­ish up stand­ing proud. The nut then pulls up tight with­out clamp­ing prop­erly, and the ta­per will slip – some­thing al­ways to watch out for. Usu­ally this is eas­ily fixed with a washer that has a hole slightly larger than the end of the ta­per. In this case, how­ever, it was not quite that easy. The shaft did in­deed pro­trude, as ex­pected, but a washer can­not be fit­ted be­cause the re­tain­ing nut has a flange to make the fly­wheel self-ex­tract­ing. In­stead, the nut had to be mod­i­fied in the lathe, to en­large its ex­ist­ing coun­ter­bore suf­fi­ciently to clamp prop­erly (PUB hopes) when it is fi­nally as­sem­bled. Mary, bless her, hoped that a pro­fes­sional power unit re­build would just leave a cou­ple of mount­ing bolts to fit and do up and the Rex-Acme would be ready again. But it doesn’t work like that, does it dear reader?

The month has not been spent en­tirely in the garage fet­tling the above. Un­for­tu­nately the Popham Mo­tor­cy­cle Megameet clashed with Brack­ley’s Fes­ti­val of Mo­tor­cy­cling, which PUB usu­ally at­tends. Re­ports say that Brack­ley was big­ger and bet­ter, but as she had never vis­ited Popham she de­cided it was about time to go there in­stead, and it was a worth­while visit. The au­to­jum­ble made a very good first im­pres­sion, with the first stand vis­ited hav­ing lots of good stuff. How­ever that one was ex­cep­tional, and sub­se­quently PUB did not find any of the very ob­scure bits she is seek­ing. Morini Alan did reck­lessly state that if the price on a lit­tle Mo­tom he spot­ted had been £500 he would have bought it. Imag­ine his cha­grin when an­other one was in­deed priced at £500 – and his ‘friends’ did not let him for­get. No mat­ter, as there were plenty of bikes to pe­ruse, in the mar­quee and al­ways out­side helps. where Some the of sun­the more shone un­usual– which bikes are il­lus­trated in the ac­com­pa­ny­ing pho­tos. Un­for­tu­nately RealClas­sic does not yet have Harry Pot­ter type holo­grams em­bed­ded in it, so the demon­stra­tion cut­away Wankel en­gine is not as in­struc­tive as at the event. An­other trip took PUB in the op­po­site di­rec­tion up to the Lin­colnshire Fens,

where Maughan & Sons is hid­den away – even more so as the nor­mal ap­proach road was closed. Whereas the VOC Spares Co. is the go-to place for Vin­cent spares, Maughan are ma­chin­ists and man­u­fac­tur­ers, as well as of­fer­ing some re­build ser­vices, and all ded­i­cated to the mar­que. In par­tic­u­lar they re­build crankshafts, and the visit proved that PUB’s pre-war assem­bly was no prob­lem, which will save her from at­tempt­ing the task with in­ad­e­quate fa­cil­i­ties (such as press and grind­ing equip­ment). How lucky she is, to be able to get this kind of ser­vice for an ob­scure ma­chine made in ‘a half for­got­ten cor­ner of Hert­ford­shire’ as Bruce Main-Smith used to say.

It was im­pres­sive to see shelves of new parts, and lots of work in progress. The clas­sic bike world is ex­tremely lucky to have spe­cial­ists such as these cater­ing for its needs – but re­mem­ber that they do have to earn a liv­ing. So parts can­not be overly cheap, or rid­ers would still be break­ing the bikes for parts as they used to, in­stead of re­build­ing them. Hence there is a cor­re­la­tion be­tween the price/value of bikes, and the spares avail­abil­ity. For the ‘big four’ as they were once known (BSA, Tri­umph, AMC, Nor­ton), where vol­umes are higher, a good spares sup­ply nev­er­the­less de­mands that the bikes hold a de­cent price, whilst for the lower vol­ume ex­ot­ica both the spares, and thus the bikes, are in­evitably more ex­pen­sive. The up­side is that with those prices sup­port­ing spares pro­duc­ers, the bikes them­selves re­main re­pairable and there­fore use­able.

Next prob­lem: where will the petrol come from when the Gov­ern­ment phases out fos­sil fuel ve­hi­cles? Ac­tu­ally the pro­posed 2040-2050 does not rep­re­sent much of a threat for PUB, as she will be well past rid­ing and prob­a­bly long gone by then, but it might even­tu­ally im­pact prices…

Wartime Ger­man side­car out­fits front Popham’s au­to­jum­ble, the vis­i­tors, and a sunny day

Ital­ian Rumi two-stroke twins were also avail­able in mo­tor­cy­cle form. These were rare in the UK, but even rarer is the Ear­les forked ‘Corsa’ model in front of the more usual stan­dard model

Pretty lit­tle two-stroke twin scoot­ers from Rumi were also ex­cel­lent per­form­ers. The very rear-set pil­lion, and light alu­minium chas­sis work re­sulted in a very light front end when car­ry­ing a heavy pas­sen­ger – es­pe­cially up­hill

There were Nor­ton ro­taries at Popham, but the Her­cules is some­what rarer, and the Van Veen (with a Citroën en­gine ac­cord­ing to proud owner) rarer still

Popham’s Wankel area pro­vided this hand op­er­ated demo to ex­plain the work­ing prin­ci­ple. Un­for­tu­nately RealClas­sic does not con­tain ‘Harry Pot­ter’ type video pic­tures

One reper­cus­sion of grind­ing in the ta­per was a need to cut back this fly­wheel boss, in or­der to main­tain clear­ance to the crank­case. A very man­ual ap­proach was taken – note the file

The Rex-Acme’s Al­bion gear­box re­turned with the kick­start not fit­ted, be­cause it didn’t fit. Some weld­ing and fil­ing later, it mag­i­cally did fit. With a spe­cially made cot­ter pin the assem­bly is now com­plete, and hope­fully will prove sat­is­fac­tory

New pivot pin is stepped and fit­ted to the worn holes so as to take out most of the slop from this clutch op­er­at­ing lever

Pit­ted main­shaft on the vin­tage Vil­liers did not sat­isfy PUB, but grind­ing in the ta­per was not with­out its reper­cus­sions (see text)

Al­though the pivot pin for the Al­bion clutch lever re­mained ser­vice­able it was very sloppy. Rather than at­tempt to bush the holes, a fit­ted pin was turned on the lathe

Once fa­mous logo of the Mon­dial mar­que – win­ners of many World Cham­pi­onships un­til the 1957 with­drawal of a num­ber of Ital­ian fac­to­ries. The FB pre­fix to Mon­dial stands for ‘Fratelli Boselli’, and the cur­rent Count Boselli is one of the movers and...

Seen at the re­cent Bill Lacey meet was this Mon­dial, a once fa­mous name. Af­ter some­thing of a failed at­tempt at re­vival some years ago, the name has now been ap­plied to a Chi­nese pro­duc­tion. How­ever, the bike is not the usual Yamaha YBR clone, but...

Tri-Greeves have been pop­u­lar spe­cials for green roads, but here is a BSA-Greeves! Proud owner ad­mit­ted that the pow­er­plant did not drop straight in, but re­quired a bit of Odgie style cut-weld-and-grind Di­a­gram of Granville Bradshaw’s oil-cooled...

Very un­usual spe­cial seen at Popham was this ‘RBS’ – an oil cooled Bradshaw ‘oil boiler’ en­gine housed in a Rudge frame

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