No spe­cial fu­els, multi-man team or cun­ning tricks – this Jap-tri­umph sprinter heads its class with good old-fash­ioned engi­neer­ing


No fancy gub­bins, no big-bucks team – this is how to go se­ri­ously fast the old-fash­ioned way

Stand­ing out at the last-ever bike meet­ing held at Shake­speare County Race­way, this 500cc Jap-tri­umph sprinter caught the at­ten­tion due to its func­tional sim­plic­ity. A se­ri­ous con­tender and hard to beat in the 500cc Vin­tage class, it turns stand­ing-start quar­ter miles in the 12-sec­ond bracket and holds the class record with 12.45s at 108mph. Yet this straight­liner has no su­per­charger, no slider clutch, doesn’t drink ni­tro-meth­ane, has a skinny 4.00 rear tyre and doesn’t need a team to fire it up.

Be­tween runs, when oth­ers were fet­tling more elab­o­rate and un­pre­dictable ma­chin­ery, its owner John Young parked the bike up and en­joyed a cuppa with his part­ner Maggs.

An ex­pert-level mo­tocross rider in the early 1970s, John got to know JAPS when he tried grasstrack­ing. He took up side­car tri­als in his mid-50s and, with son Paul as pas­sen­ger on an Ariel HT5 out­fit, won seven Pre-’65 cham­pi­onships. He re­tired from his job as a car me­chanic in 2015 at the age of 70, but rather than put his feet up he does a bit of bike sport. In re­cent years, he’s pi­loted a Yamaha Xt500-pow­ered out­fit in long-dis­tance tri­als with friend John Hind, top­ping their class in the Land’s End Trial, the Ex­eter Trial and the Ed­in­burgh Trial. And, of course, he races this spe­cial sin­gle.

Built in 2003, the bike con­forms to Vin­tage (pre-1946) rules, be­ing based on a 1936 Tri­umph Tiger 70 frame and girder front forks. The en­gine is a true clas­sic, the sin­gle-cylin­der 497cc (80 x 99mm) JAP unit that dom­i­nated speed­way from the 1930s to the 1960s. The pre-war ‘five-stud’ type, with five cylin­der and head through-bolts in­tro­duced in 1935 to beef-up JAP’S orig­i­nal four-stud speed­way mo­tor, it’s a pure rac­ing en­gine with the main bear­ings, big-end and rocker bear­ings all caged-roller

units. Pushrods bear di­rectly on roller-type cam fol­low­ers, ac­tu­ated by what John calls ‘good cams’. Non-stan­dard fea­tures are the mod­ern Car­rillo steel con­rod on a Jawa big-end as­sem­bly, and also the crankcases. “Orig­i­nally these en­gines had a mag­ne­sium crank­case, which tends to split be­low the bar­rel flange on the drive side,” John ex­plains. “You can weld them up but they only last one week­end, so I had four new sets made in alu­minium al­loy.”

The cast iron cylin­der and head have shal­low finning suf­fi­cient for short dashes at full power on cool-run­ning al­co­hol fu­els. Car­bu­ra­tion is by a brass-bod­ied Amal with an al­loy in­take stack and re­mote float cham­ber (John quotes the main jet size as “about 1025, or an eight­inch drill bit”). Sparks are pro­vided cour­tesy of a BTH mag­neto.

Lu­bri­ca­tion is the orig­i­nal to­tal loss, an ex­ter­nal Pil­grim pump fetch­ing oil from a tank un­der the min­i­mal seat which col­lects in a cham­ber be­side the lower crank­case af­ter cir­cu­la­tion (it would orig­i­nally drip out). A tube guides it to a catch bot­tle be­hind the gear­box, and to pre­vent track

con­tam­i­na­tion John dis­creetly slips a panty liner into a tray un­der the sump.

The unit is fa­mous for strong bot­tomend torque and, with a com­pres­sion ra­tio of 13.5:1, John es­ti­mates out­put at close to 50bhp. He has the en­gine ‘looked at’ by oc­to­ge­nar­ian JAP spe­cial­ist Gerry Good­win.

The four-speed gear­box is the 1930s-1940s Nor­ton type, nick­named the ‘doll’s head ’box’ be­cause of the selec­tor cover’s shape, and has split-sec­ond-sav­ing close ra­tios. The three-spring dry clutch is also Nor­ton, and an im­por­tant part of the bike’s speed. “Get­ting a good time is all in the take-off,” John says. “On a grippy sur­face you can’t just drop the clutch, as

the front wheel will come up and chances are you’ll end up on your back­side. It’s some­thing that takes prac­tice – you couldn’t just get on that bike and do it.”

In a meet­ing in­ter­rupted by rain, John didn’t break any records but ran re­spectable up­per 12s with 104mph ter­mi­nal speeds. John was also rid­ing de­spite a hand in­jury. The JAP can be push-started, but a cou­ple of months ear­lier at the Montl­héry Vin­tage Re­vival he bor­rowed a foot-op­er­ated elec­tric starter. In the heat of the mo­ment, part of his right fore­fin­ger was sev­ered when it got caught be­tween the fi­nal drive chain and the rear wheel sprocket.

Who says you have to be sen­si­ble af­ter you’ve en­tered re­tire­ment?


ABOVE: John Young’s straight­liner is a fine ex­am­ple of an old-school min­i­mal­ist sprinter

While other OAPS are out dressed in whites on the bowls green, John’s leathered up

John’s in his 70s, but he still loves to do a quar­ter mile in the up­per 12s

If you get this close, you’ve al­ready said good­bye to your ear drums

Fuel from lo­cal petrol sta­tions flows through the taps

This has to deal with de­cel­er­a­tion from 104mph...

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.