Com­bine the best parts

On the face of it, there are some bikes which shouldn’t work – wrong bits, too old fash­ioned – yet de­spite such odds they do work.

Classic Dirtbike - - Contents - Words and pics Tim Britton

Which is what the ail­ing BSA/ Tri­umph group did with the Tri­umph 500 en­gine and the B50 MX chas­sis to pro­duce pure gold.

Those of us who were young­sters in the early Sev­en­ties and read­ing the mo­tor­cy­cle press of the day had ab­sorbed ev­ery­thing about the ISDT, the long dis­tance tri­als where Tri­umph had ex­ceeded all ex­pec­ta­tions and pro­duced win­ners. We had fo­cussed on such mo­tor­cy­cles as the TR5, the Tro­phy 500, we knew all about the wartime leg­end of the square bar­rel over the later round bar­rel, how could we not, it was writ­ten down in front of us.

We knew the ISDT was the ul­ti­mate test of mo­tor­cy­cle and rider and that the com­pe­ti­tion de­part­ments of not only Meri­den were fo­cussed on suc­cess in this de­mand­ing theatre of skill and de­ter­mi­na­tion. We knew the mo­tor­cy­cles needed for this ul­ti­mate test would be su­perb in every re­spect… if only they would pro­duce them in huge num­bers then the in­dus­try would rise again.

Some of us as­pired to the skills the ISDT rid­ers demon­strated, from their calm rid­ing styles keep­ing them on time, to tyre changes in less than four min­utes – this, we thought, was the way for­ward. We ached to be there on Tri­umph twins, couldn’t wait to be in­volved; but per­haps we were naive as these team mo­tor­cy­cles were never pro­duc­tion bikes in the true sense. Yes, they were bikes that had be­gun as pro­duc­tion-based ma­chines but af­ter be­ing hauled from the pro­duc­tion line they were looked over very care­fully. Then a few mods here and there to make them more suit­able for pur­pose and so it went on. At least it went on un­til the in­dus­try all but died and cost cut­ting came in, gone were the base mod­els these ma­chines were culled from.

You see what we dirt mad young­sters didn’t ap­pre­ci­ate was such off-road bikes were small pota­toes com­pared to the road mar­ket and what the fac­tory hi­er­ar­chy in place didn’t re­alise was mo­tor­cy­cles had be­come leisure. Gone was the need for daily trans­port as a ne­ces­sity, those who rode a mo­tor­cy­cle to work did so be­cause they chose to do so, not be­cause they couldn’t af­ford a car. Per­haps that was the re­al­i­sa­tion which dawned on the fac­tory hi­er­ar­chy af­ter end­ing pro­duc­tion of the high piped T100; maybe, maybe not, but it is a plau­si­ble ex­pla­na­tion.

Ar­guably, con­sid­er­ing the dual pur­pose back­ground both Tri­umph and their own­ers BSA had, it is in­con­ceiv­able both ended up at a point in the Sev­en­ties with no ma­chine in the range to ser­vice the grow­ing trail bike need in the USA. How­ever, I wasn’t there in those board­rooms where things were dis­cussed and to me it seems the ob­vi­ous thing is to spot a need and ful­fil it but I

sup­pose by then the in­dus­try was peo­pled with those who found con­cept meet­ings, fo­cus groups and think-tanks to be im­por­tant rather than just ask­ing those who might know.

One per­son who might have known was Bill Baird the multi-en­duro cham­pion in the USA who favoured Tri­umphs to the end of his ca­reer. Bill’s fame as an en­duro rider and the fact he was seen on re­mark­ably stan­dard look­ing Tri­umphs prob­a­bly helped no end in the task of sell­ing dirt bikes. In those days, Tri­umph’s 500cc range was based on the unit con­struc­tion pack­age and while there might have been a few de­tail dif­fer­ences, the frame, forks, yokes and en­gine were the same.

In­side the en­gine spec­i­fi­ca­tion could and did vary de­pend­ing on what use the model would be put to, but aside from that a road­go­ing 500 and a com­pe­ti­tion 500 are not a mile apart. Then it all ended as the smaller range was dis­con­tin­ued or re­duced and ef­fec­tively be­came the Day­tona road bike.

By the early Sev­en­ties, the Bri­tish in­dus­try had to all in­tents and pur­poses gone, there were no vast works sup­ported com­pe­ti­tion teams – even if there had been for the of­froad­ers at least there was lit­tle for them to ride. But there was still in­ter­est in sell­ing mo­tor­cy­cles and more im­por­tantly maybe the re­al­i­sa­tion the Bri­tish bikes had had their high per­for­mance day, so maybe a gen­tle dual pur­pose ma­chine would be of in­ter­est. With Tri­umph’s flex­i­ble en­gine, BSA’S chas­sis de­sign avail­able, there didn’t seem any rea­son not to put the two to­gether and see if a few couldn’t be shifted.

Though the new Tro­phy Trail and later Ad­ven­turer were un­likely to be huge sell­ers at that stage in the in­dus­try, any sales would be wel­come. BSA’S re­main­ing works rid­ers were drafted in to test the pro­to­type, even the Army in the guise of Sergeant Ge­orge Webb, did their bit and the re­sult was a de­cent ma­chine. John Nut­ting got hold of one for a

while and found it to be a pleas­ant ma­chine, but not re­ally one to ride at higher speeds on the road; but for green lanes, back roads and that sort of thing then this could well have been the bike to go for. With the frame bear­ing oil and based on BSA’S MX bikes, han­dling was classed as lively and its styling a cu­ri­ous mix of Six­ties and the decade style for­got… sorry, the Sev­en­ties I mean. With an en­gine pro­file con­ceived in the Fifties and with­out the re­sources of the new fac­to­ries on the block to re­design the power base, any­thing head­ing out of Meri­den in those days was al­ways go­ing to look dated in the Sev­en­ties. That said, as Eric Cheney proved, there was no rea­son why an up­dated chas­sis shouldn’t house an older mo­tor and do well.

So the Tro­phy Trail, or TR5T or Ad­ven­turer, all largely the same mo­tor­cy­cle and with a lot of road equip­ment fit­ted, was hoped to do well in the USA where vast tracts of land were still open to ride on. The ma­chine was ex­pected

to be a great one for fire trails rather than se­ri­ous off-road work where it was felt to be in need of a firm and bold hand if any­thing like dif­fi­cult ter­rain was to be en­coun­tered.

The Mo­tor­cy­cle’s tester in 1972 found the Ad­ven­turer would per­form as well with a pil­lion as it did solo, nor did it mat­ter all that much if the rider were stood or seated. Crit­i­cism was aimed at the brakes and electrics though as hit­ting the first wa­ter splash brought the com­ment “…af­ter the ford, or in­deed af­ter heavy rain, the en­gine stopped but the brakes wouldn’t…” These points were ad­dressed when a few of the ma­chines were con­verted into a more se­ri­ous com­pe­ti­tion spec for the 1973 ISDT. CDB cov­ered just such a ma­chine in is­sue 37, when we fol­lowed Chris Oliver’s in­ter­pre­ta­tion of the 1973 ISDT team bikes. What was spe­cial about Chris’s bike was he had been in the USA as part of the UK or­gan­is­ing team and had first-hand knowl­edge of those su­perb ma­chines built from stan­dard TR5TS at Duarte in Cal­i­for­nia.

How­ever, that was still to come when The Mo­tor­cy­cle claimed the bike was, at 3cwt on the road, a rel­a­tively light ma­chine. Three hun­dred­weight equates to 336lb or 152.4kg and that was sup­posed to be light… it was still 40lb heav­ier than the square bar­relled Tro­phy of 1949.

The press praised the more tra­di­tional feel of the power de­liv­ery while sug­gest­ing a the­o­ret­i­cal top speed of per­haps 82mph, though hinted the rider’s teeth may have vi­brated slack by then. The is­sue of weight came up again and it is one of those para­doxes where a heavy mo­tor­cy­cle can feel lighter than a light mo­tor­cy­cle de­pend­ing on the weight dis­tri­bu­tion. The tester of the day felt the weight to be a mi­nor is­sue as once on the go it was al­most un­no­tice­able.

Typ­i­cally of the time though, in an 800 mile test there was praise for min­i­mal oil con­sump­tion and sur­prise at the level of

me­chan­i­cal noise from the en­gine. This com­ment comes on the back of grow­ing noise pol­lu­tion com­plaints ex­cept ‘noise pol­lu­tion’ hadn’t been in­vented. In or­der to op­er­ate with a mod­icum of con­sid­er­a­tion for the rest of the planet’s oc­cu­pants a weird and won­der­ful pressed steel si­lencer had been de­vised. This proved so ef­fec­tive at deal­ing with ex­haust noise that en­gine clat­ter could now be heard. Praise too came for the front forks which had ben­e­fited from be­ing de­vel­oped in the scram­bles world and smoothed out all bumps with nary a flut­ter.

With around 2500 of­fi­cial ex­am­ples of the TR5T in its two main model des­ig­na­tions, this ma­chine is fairly rare, even for Tri­umph and as such com­mands quite high prices. How­ever, if you’re pre­pared to com­pro­mise on some de­tails it’s not that dif­fi­cult to build a replica, or in­deed a replica of most ISDTesque Tri­umphs of the Six­ties as most used off-the-shelf com­po­nents.

Even the big­ger Tri­umphs, such as the 750 range, joined in the off-road fun with the TR7T in 1981. Rather like the TR5T, it was not meant to be a se­ri­ous dirt bike but an early ad­ven­ture bike which would cope with the dirt of ba­sic high­ways and by­ways of the UK and USA. A shame that time caught up with it and re­ally it ought to have been pro­duced 10 years ear­lier… to fi­nalise, the Ad­ven­turer, Tro­phy Trail and TR7T have all got their place in the of­froad scene as ma­chines be­com­ing so much more than the sum of their parts. )

... the press praised the tra­di­tional power de­liv­ery, sug­gest­ing a teeth­slack­en­ing the­o­ret­i­cal top speed of 82mph...” per­haps

Pretty much a last gasp for Tri­umph, cer­tainly for the 500s at least, but what a great look­ing bike.

Witha­mul­ti­tude of cams, valves, pis­tons, gears and car­bu­ret­tors avail­able to se­lect from, Tri­umph’s unit 500 could be built in any spec from hot racer to flex­i­ble off- roader. As stan­dard, the Tro­phy Trail would come with in­di­ca­tors but a lot of own­ers would re­move them as they’re quite vul­ner­a­ble.

No mis­tak­ing the­model is there? …as it was for the in­stru­ments too. Made in Eng­land… maybe… but proved in the USA ISDT 1973. The ef­fects of vi­bra­tion were at least be­ing ad­mit­ted and some at­tempt to flex­i­bly mount the head­light was ap­pre­ci­ated...

Ex­haust sys­tem could per­haps be a bit vul­ner­a­ble and orig­i­nal sys­tems are rare these days. Gir­ling oil damped rear units were soon to be out­classed in the Sev­en­ties, big alloy rear hub worked okay but for the ISDT Tri­umph used the BSA qd type.

Top­ping off the frame was the smartest look­ing tank to be fit­ted to a Tri­umph ever… dis­cuss and let me know your thoughts. Pil­lion rests – or per­haps ‘buddy pegs’ would be a bet­ter term – though given the seat di­men­sions the buddy would have to be re­ally close… and small. Tri­umph had timed breathers worked off the ex­haust cam, then some­one thought “let’s do away with them, and put a big tube in the pri­mary case…” it works too. For the Tro­phy Trail, Tri­umph used the par­ent group’s Ce­ri­ani- style front fork which also fit­ted other mod­els in the range, hence the ex­tra brack­etry. No, it’s not stan­dard but Bryn de­cided to leave it on any­way as it is use­ful and a fairly neat at­tach­ment. Rear light unit is ac­tu­ally mas­sive and also pro­tected from the vi­bra­tions pro­duced by the en­gine.

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