CDI
A big g part rtt of the 5bhp boost in peak power is the Slovenian-made Zeeltronic electronic CDI that is now fitted to the bike, a programmable system that allows the advance curve to be varied very readily.
BARTOL 250 Engine:
Watercooled, parallel-twin, rotary-valve, two-stroke with 180° crankshaft and six transfer/three exhaust ports Dimensions: 54 x 54mm Capacity: 247cc Output: 76bhp at 12,000rpm (at rear wheel) Carburation: 2 x 37mm Mikuni flatslide Ignition: Zeeltronic electronic CDI Gearbox: Six-speed Yamaha Clutch: Multiplate dry Yamaha Chassis: Aluminium tubular duplex cradle frame Suspension: Front: 40mm Kayaba telescopic fork; Rear: Braced extruded aluminium swingarm with White Power monoshock and rising rate link Head angle/trail: 27.5°/110mm Wheelbase: 1330mm Weight: 104kg with oil/water, no fuel Brakes: Front: 2 x 260 mm Brembo stainless steel discs with two-piston Brembo calipers; Rear: 1 x 200mm Zanzani aluminium disc with single-piston Brembo caliper Wheels/tyres: Front: 120/70-16 Avon AM22 on 3.00in. Marvic cast magnesium wheel; Rear: 150/70-18 Avon AM23 on 3.00in. Marvic cast magnesium wheel Top speed: N/A Year of construction: 1983 Owner: Alta Engineering Ltd, Barnsley, Yorkshire, Great Britain
But it was all too late – and I never did get the Aussie guy’s name to thank him!”
The Yorkshireman
However, Harald’s main helper in creating the flawed Bartol 250GP bikes was English, not Austrian – or Australian! Yorkshireman Alistair Taylor, now 69, is a 20-year veteran of the Grand Prix paddock, who during his time as variously a race mechanic, team coordinator, motorhome driver and paddock parts supplier, worked with a host of riders ranging from Mick Grant, Richard Schlachter, Cliff Carr and Graeme McGregor, to Eddie Lawson, Gustl Auinger, Carlos Lavado and Martin Wimmer. Fluent in German, Alistair had found himself out of work in the 1976 Finnish GP paddock at Imatra after a bust-up with Alex
George, who he’d been working with for all of six weeks! It was a watershed moment in his wrench-wielding career. “I’d known Harald Bartol for two years, and he was such a nice guy,” recalls Alistair. “He had this super-fast 125 Morbidelli he’d tuned himself – it was engine number 1005, so only the fifth one made. My mate Derek Booth, an ex-sidecar passenger from Doncaster, who had worked for Jack Findlay until Sweden, had also jumped ship from Jack and started working for Harald and Karl Auer, another Austrian guy who raced 500 and 350. They were in Finland with four bikes and two riders, and they’d not been able to find anybody in Austria to come all the way up to Finland to help them. Derek knew I’d left Alex and was doing nothing, so he said: ‘Can
Riding the bike Having written about the Bart rtol t 250/350 project during my early days as a GP report rter, t it was very satissfying to finally ride one, which, thanks to Manfre ed John and his Klassik Motorsport rtt organisattion team, I was able to do in practice for the Francciacort rta t round last year. I found d this tweaked incarnation gives a much greater sp pread of torque than expected from a 37-year--old rotary-valve engine. Before the developm ment of exhaust powervalves, these had a very fierce transition into the power band, and a narrower spread of power and torque, with more power tha an a piston-port rtt or reed-valve design. Instead d, the Bart rtol t 250 off ffers f the best of both worlds, because there’s a strong, smooth transition n into the rotary-valve motor’s strong powerban nd above 8500rpm, as well as the torque delivery I’ve only experienced before on a twostroke 250 from a powervalve-equipped motor. During my three 20-minute sessions on the bike I had seveeral drag races out of the Franciacort rta t hairpin with later 1990sTZYamahas and despite my extra weight compared to a typical 250GP jockey, the Bart rtol t kept up with them. In my first session I ended up having a great battle witth a well-riddenTZ250, whose rider was braver than me on the brakes going into the infield secction of the track, only for me to be able to outdra ag him out of the e slo owe er bend ds.Thiss wa as despite th he gear-lever being a fraction too low for me to shift ftt gear properly on the brakes, so I would occasionally enter a turn one gear higher than I had d intended. For all the wrong reasons this unde erlined the forgiving nature of the Bart rtol’s t motor – not a term you usually relate to a rotaryvalve motor – as well as the great grip from the Avon tyre es as I cranked the bike over furt rther t than intended to cope with the extra turn speeds. For my y second session Alistair positioned the gear lever better for me, so I was better able to start rtt ridin ng the Bart rtol t in something approaching anger.Third time lucky it all came together, and I could really appreciate the qualities of the Bart rtol t motor – as well as the Bakker frame. It was stable round Fra anciacort rta’s t fast sweeping right-handers, and nimb ble handling in the infield turns.The Bart rtol t bra aked well, too, the twin front Brembo discs with h their Serie Oro calipers stopping the 104kg hallf-dry bike and its rider very capably from fift fth t gear down the pit straight. But the e real star of the show is that excellent engine – in my last couple of laps of my third session I inched closer to a 1990sTZ250 with its later V-twin reed-valve motor complete with powervalve. I can confirm that the rotary-valve Bart rtol t was the equal of this 10-year younger motorcycle in a straight line, as well as just as strong on acceleration out of a slow turn and a third-gear sweeper. Mission accomplished, Harald, and kudos to Alistair Taylor and Leif Nielsen for helping to prove the value of your engineering skills 37 years on.
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