Su­per pro­file

With fac­to­ries in tur­moil and slid­ing to obliv­ion, the ACU had to look else­where for ISDT team bikes… en­ter the Cheney Tri­umph.

Classic Dirtbike - - Contents - Words and pics: Tim Brit­ton

The world yelled ‘light­weight’ the Bri­tish said ‘Cheney dear boy’ and cre­ated a le­gend in ISDT, we look at the ex-jim San­di­ford 504cc ISDT Gold Medal win­ner.

Some­times the best look­ing mo­tor­cy­cles are cre­ated by ac­ci­dent or ne­ces­sity rather than by de­sign. For in­stance had the Mc­can­d­less broth­ers not felt Nor­ton’s post World War Two tri­als bike was a bit un­wieldy and set about cre­at­ing their own from Nor­ton parts, then the 500T would not have seen the light of day. Road en­thu­si­asts can point a fin­ger at Ed­die Dow’s con­ver­sion of a BSA A10 to Goldiesque style which forced BSA’S hand to pro­duce the Rocket Gold Star. In the same way a need for ISDT suc­cess and the lack of a suit­able stan­dard prod­uct led to the in­tro­duc­tion of the Cheney Tri­umph and cre­ated an ISDT le­gend, repli­cas of which are highly sought af­ter.

In 1970 the rules for the ISDT changed to re­flect the tur­moil in the mo­tor­cy­cle in­dus­try world­wide. Since its in­cep­tion in 1913 the In­ter­na­tional Six Days Trial had in­cluded a Tro­phy and a Sil­ver Vase com­pe­ti­tion within its frame­work. The Tro­phy was the premier con­test with par­tic­i­pants mounted on ma­chines made in their home coun­try. The Sil­ver Vase con­test al­lowed rid­ers to use any ma­chine. As the world­wide in­dus­try was shrink­ing, this meant the Tro­phy con­test had fewer and fewer el­i­gi­ble teams and the Sil­ver Vase was be­ing seen as the more de­sir­able con­test. So to coun­ter­act this, both con­tests were thrown open to na­tional teams mounted on any make of ma­chine.

How­ever, the Tri­umph unit twin en­gine had a good rep­u­ta­tion in the ISDT – fast, flex­i­ble and re­li­able – all it needed was to be mounted in a more suit­able frame than the stock Tri­umph one. The MX world had been us­ing af­ter-mar­ket frames for years and Eric Cheney’s chas­sis had a good rep­u­ta­tion. With Bsa/tri­umph un­will­ing or un­able to sup­ply com­plete bikes the an­swer was to fit a twin en­gine into Cheney’s frame.

How­ever, it was not to be quite that sim­ple as out­side fac­tors con­spired to de­lay the con­struc­tion of the bikes. The big­gest of these prob­lems in­volved a strike at the Dun­lop fac­tory which held up the sup­ply of the cor­rect high ten­sile steel rims. In the end a wheel build­ing spe­cial­ist came to the res­cue and sourced enough rims from his own stock to com­plete the job. Cheney and his team worked flat out the week­end be­fore the Welsh Two-day Trial so the team mem­bers could test their ma­chines.

The bikes them­selves bris­tled with the spe­cial re­quire­ments of an ISDT rider and a lot of thought had gone in to their con­struc­tion. Start­ing with the Cheney oil-bear­ing frame, a cen­tre stand had been added so wheel chang­ing was eas­ier and rock guards added to pro­tect the en­gine. Cheney’s front forks were used and his own Elek­tron front hub too, while at the rear was BSA’S crin­kle hub – a long time favourite for such ma­chines. In­ter­nally the en­gine was to Tri­umph’s Day­tona spec­i­fi­ca­tion but with a lower first gear ra­tio. In their fea­ture on the ma­chines in 1970 Mo­tor­cy­cle re­vealed all ma­chines for the Welsh would be 490cc but af­ter the event two would be en­larged to 504cc for use in the 750cc class and all bikes would have their com­pres­sion ra­tio low­ered to 8:1 from 9.5:1 as it was felt the fuel avail­able in Spain where the ISDT was

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