34 Cre­at­ing a leg­end

Cat­a­logue cor­rect doesn’t of­ten cut it on the track, where per­for­mance is all.

Classic Dirtbike - - Contents - Words: Tim Brit­ton Pics: Gary Chap­man

Putting a Tri­umph engine in a BSA frame makes a… Beezumph… hmm that name is taken… how about TRIBSA…?

In the mo­tor­cy­cle world there are any num­ber of rea­sons to cre­ate a spe­cial with com­po­nents from var­i­ous sources. These rea­sons range from ‘couldn’t af­ford a cat­a­logued ma­chine’ to ‘the stan­dard of­fer­ings weren’t right’ and of­ten in­clude ‘had a load of bits’ and ‘sheer bloody-mind­ed­ness’, to give just four ex­am­ples. Some such spe­cials or ‘bitzas’ are more com­mon in one sphere of the sport­ing world than oth­ers, for in­stance the com­bi­na­tion of Tri­umph engine in a Nor­ton frame is evoca­tive of the café racer scene, while slip­ping a Tri­umph engine into a BSA frame is much more com­mon in the scram­bles world. The re­sult­ing TRIBSA was and is ar­guably a bet­ter club­man ma­chine than the BSA Gold Star that of­ten do­nated the rolling chas­sis. Now be­fore the Gold Star Own­ers’ Club gangs up on me, I have to say the Goldie is a su­perb ma­chine – but in or­der for it to pro­duce the best it can do, a com­pre­hen­sive main­te­nance sched­ule has to be fol­lowed, as it is pretty much a race engine. The prob­lem was, not all club-level rid­ers could af­ford the main­te­nance and parts that had to be re­placed or re­built af­ter a cer­tain num­ber of hours. There was a ten­dency to think ‘we’ll get an­other meet­ing out of it...’ and all of a sud­den there’s an engine-shaped hole where the engine used to be.

Luck­ily Tri­umph’s ver­sa­tile twin engine was rel­a­tively cheap and much more eas­ily main­tained by the en­thu­si­ast watch­ing the pen­nies, and it wasn’t dif­fi­cult to fit into the BSA frame. Those who had the Gold Star chas­sis got quite a high spec, but there was no real need to go that far as even the B31/B33 and the later swing­ing arm A7/A10 chas­sis was an all-welded one to the same di­men­sions as the Goldie. Okay, so it had a few more brack­ets and what­not, but hack­saws and files sorted that out and the twin frame didn’t have the oil pump kink in the lower frame rail – but with a Tri­umph engine, it didn’t need it.

Af­ter that it was up to the rider/builder and the suc­cess or oth­er­wise of the project would de­pend on the abil­ity of those in­volved in it. There was no rea­son why mar­ry­ing a Tri­umph engine into a BSA chas­sis couldn’t pro­duce a win­ning com­bi­na­tion, as that was what the Rick­man broth­ers did with their Metisse be­fore they be­gan to build their own frames. There was an ar­che­typal ‘look’ for the TRIBSA and in or­der to be con­sid­ered se­ri­ous, cer­tain com­po­nents had to be used in the build. Though things are slightly dif­fer­ent now, in the glory days no self-re­spect­ing TRIBSA would be seen with­out Nor­ton forks keeping the front end up, or ei­ther the BSA or AMC com­pe­ti­tion gear­box tucked in be­hind the engine. As for the engine, Tri­umph hand­ily pro­duced an all-al­loy 500 which was nice and light and had a full pack­age of cams, pis­tons and car­bu­ret­tors ei­ther off the shelf at the dealer or in the breaker’s yard. Some al­loy sheet, a bit of hack­saw­ing and fil­ing, then drilling to make the engine plates, and it was start­ing to look like a bike now. Royal En­field made an al­most stream­lined pri­mary case and a Manx Nor­ton clutch fit­ted in­side it quite nicely, thank you. If the bud­get ran to it, ei­ther a Manx or 7R rear wheel could be used, though these were not com­mon and the bench­mark BSA crin­kle hub tended to be the choice of most peo­ple. Up at the front there were lots of choices avail­able, but most tended to set­tle for a sin­gle-sided hub ei­ther from the Goldie or some other model in the BSA range. The scal­loped 500T Nor­ton hub too was seen, or maybe they were the stan­dard hubs with a few scal­lops taken out care­fully.

Some al­loy mud­guards, al­loy fuel and oil tanks which could be bought or made if the skills were there, a cut-down sad­dle, scram­bles bars and con­trols, a pair of knob­bly tyres, and the TRIBSA was ready for ac­tion. Tri­umph’s engine pro­duced nice, flex­i­ble power and could be im­proved as the rider pro­gressed; there were big­ger en­gines if the class al­lowed and so on.

The TRIBSA cer­tainly filled the gap be­tween the demise of the fac­tory four-strokes and the rise of the re­li­able two-strokes and even when the two-strokes did ar­rive, the era of the spe­cial was not over. This is where the sheer bloody-mind­ed­ness of­ten dis­played in our sport kicked in, and mut­ter­ings were along the lines of ‘I know the BSA Vic­tor is lighter and just as fast but damn it, I like rid­ing the TRIBSA…’ No one ever said our sport was ruled by com­mon sense.

En­ter the clas­sic scene, be­cause there are those who pre­fer to race older mo­tor­cy­cles be­cause the ta­ble-tops, dou­ble jumps, loop the loops and so on which you sim­ply have to do – ahem, yes, a bit tongue in cheek there – in mod­ern MX aren’t for the likes of us and the sound of the older bikes is good too. In the early days of clas­sic sport the bikes were rid­den by lads who’d had them back in the day and tucked them in the shed as the re­al­ity of rac­ing say a Goldie against an RM500 in the mod­ern scene kicked in. Now with an ex­cuse to get out there, these ma­chines were hauled out and the same prob­lems arose in the clas­sic scene as they had in the ear­lier pe­riod. These prob­lems in­cluded sup­ply and de­mand; not enough Goldies, or G80CSS, or what­ever your cho­sen clas­sic for the racer was, but still lots of BSA frames and Tri­umph en­gines avail­able. These days there are some se­ri­ously stun­ning bikes as it seems we – as a col­lec­tive rather than just you and I – have a shilling or two more to spend on our hob­bies and build­ing a spe­cial with a BSA frame and a Tri­umph engine isn’t as daunt­ing as it used to be.

A field in Northamp­ton early in 2018

Taking a trip to Northamp­ton for the Northamp­ton Clas­sic Club Ltd’s Clas­sic Scram­ble proved pro­duc­tive for the CDB team, at least as far as bikes to write about were con­cerned and we, pho­tog­ra­pher Gary Chap­man and I, came away with full mem­ory cards in his case and a full notepad in my case.

Turn­ing up early on day one we caught peo­ple be­fore they were fully aware of what was go­ing on and they agreed to be posed here, there and ev­ery­where, which is how we trapped Dave God­ley. Just lin­ing up his bikes for the week­end, we asked if his pre60 TRIBSA could be pulled for­ward so that we could take some pics. Then, be­fore he could es­cape, I asked him about the bike in great de­tail.

Clearly the bike was built for go­ing rather than show­ing – all Dave’s ma­chines fol­low this ethos, which is a good thing as there’s lit­tle point in look­ing at a shiny bike while all the fun is on the track. While it does look typ­i­cally pe­riod, there are a few no­table things which help it in the mod­ern world. As Gary caught the light here, the re­flec­tion there and that sort of thing, Dave told me the frame was a replica rather than a gen­uine Bsa-made one and as such was a lit­tle lighter than stan­dard. “It’s to all the same di­men­sions as a BSA frame and un­less I tell you it’s a replica it isn’t ob­vi­ous though there is a clue...” Looked fine to us; look­ing over the bike so I could ask per­ti­nent ques­tions or show my ig­no­rance de­pend­ing on your view, the ‘clue’ be­came ob­vi­ous… it’s an oil-in-frame chas­sis.

I saw the pop­u­lar Ariel swing­ing arm in place. Now BSA did a nice tubu­lar one which was stiff enough un­til the ac­tion got dirty and it could twist or flex. Ariel – at the time owned by BSA – had this ob­long sec­tion swing­ing arm with di­men­sions more akin to the old Forth Road Bridge. This swing­ing arm went on to the HT and HS Ariels and maybe other mod­els too, but once fit­ted it was strong and kept the rear wheel in line. In the rear end of the swing­ing arm is BSA’S crin­kle hub, which joined the range in the For­ties, was still used on var­i­ous mod­els 20 years later and even when the group de­cided to tackle the ISDT one last time in the leg­endary 1973 Amer­i­can event, the rear hub of choice was a ‘crin­kle.’ Up at the front though it’s a dif­fer­ent story… “What the heck is that be­he­moth in the forks?” I gasped. “It’s from a Nor­ton Dom­i­na­tor twin,” grinned our man. “It works but per­haps isn’t as stylish as some other front hubs.” Hmmm, I would al­low that with the out­put from a 750cc TR7 top end on the 650 bot­tom end on tap then per­haps ‘works’ over ‘stylish’ wins out. Any­way, keeping that hub in place is a pair of Nor­ton Road­holder forks but with Mar­zochi in­ter­nals. “This con­ver­sion was done by Bow­der En­gi­neer­ing about 10 years ago,” said Dave. “The bil­let yokes are theirs too but would have orig­i­nally had Bul­taco forks in them.” The ac­tual Bulto forks aren’t le­gal for pre60, nor are Mar­zochis for that mat­ter, but their in­ter­nals are and few peo­ple will use the stan­dard forks these days.

We’ve touched on the engine as hav­ing a later 750 top end on it. This has a four plug head fired by a PVL elec­tronic ig­ni­tion and the idea be­hind the four plugs – two per cylin­der – is to give a more con­trolled burn rate and a touch more power from a higher com­pres­sion ra­tio al­lowed by su­per un­leaded petrol. The elec­tronic ig­ni­tion, which­ever make is cho­sen, has to be the best in­ven­tion ever in the his­tory of ever­dom for users of old mo­tor­cy­cles; re­li­able sparks come rain come shine. A spe­cial has lit­tle need to ad­here to any par­tic­u­lar com­po­nents un­less there are spe­cific rea­sons for them to be used. Our builder chose to fit bet­ter parts and AMC’S gear box as used by lots of bikes in the range, right up to the Nor­ton Com­mando even­tu­ally, is a strong and tough unit. “There’s just the stan­dard clus­ter in there,” said Dave. “I’ve mounted the footrest on the end cover as you can see but you can’t see the Suzuki clutch in­side the pri­mary case, I’m plan­ning on chang­ing it to a Nor­ton one though.” With the engine and gear­box of­ten from dif­fer­ent ma­chines, there could be some is­sues with lin­ing ev­ery­thing up as mount­ing point width may well be dif­fer­ent. In re­al­ity this isn’t a prob­lem as ac­cu­rate mea­sur­ing with all com­po­nents in place will show if dis­tance pieces are needed or per­haps a lit­tle bit of ma­chin­ing to ease off a lug here or there. As long as the engine plates bolt up and hold the engine and gear­box in place, all will be well. Way back in the early days of the clas­sic mag­a­zines there was a se­ries aimed at the road rac­ing scene in which a known name of bike build­ing re­vealed a few se­crets to suc­cess, one be­ing he al­ways bolted things to­gether from the rear of the chas­sis with the fi­nal pieces be­ing the front engine plates. Along the way, any dis­tance pieces were made and fit­ted. This gave a stress-free build – stress of the com­po­nents we mean as no build is stress free for the builder.

On the rear end of this TRIBSA are NJB shocks. A de­vel­op­ment of the Gir­ling units which were for so long an in­dus­try stan­dard, these units work well and are re­build­able, as well as look­ing pe­riod too. “I’ve an Amal Con­cen­tric carb on, I use Mor­ris Heavy Duty V-twin 20/50 in the oil reser­voir, not sure what else I can tell you,” Dave said. “Pri­mary cases?” I asked. “Early A10, han­dle­bar con­trols are a side-pull throt­tle, Amal levers and Ren­thal bars, though I made the foot brake lever.” In the end, though the TRIBSA may well have a few mod­ern touches, it’s still a clas­sic ma­chine and all credit to Dave God­ley for wrestling it around what turned out to be a fairly muddy track with peo­ple slith­er­ing all over the place.

Clas­sic looks and style from the mix ofTri­umph and BSA.

Pretty much the clas­sic ‘look’ for a TRIBSA, an AMC gear­box is fit­ted here. BSA’S ‘box works just as well if one is avail­able.

Few peo­ple these days don’t use a sidepull throt­tle. They were avail­able in the era – BMW used them – but it took a long time for the com­pe­ti­tion scene to adopt them.

Front sus­pen­sion didn’t come any bet­ter than Nor­ton Road­hold­ers in the Fifties; how­ever, 60 years on, most peo­ple hide mod­ern in­ter­nals in the old legs… won­der if that can work for rid­ers?

As rear hubs go, the ‘crin­kle’ from Small Heath is a de­sir­able fit­ment, get one if you’re build­ing a spe­cial.

De­scribed by the owner as ‘an ugly lump but it works’ the sls drum was orig­i­nally from a Nor­ton Dom­i­na­tor.

It helps, when fit­ting dif­fer­ent en­gines into BSA frames, that phys­i­cal di­men­sions of var­i­ous twin mo­tors are sim­i­lar.

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.