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17.03.2014, 22:08
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1971 BMW F750 Butler & Smith Factory Racer Engine no. 001 298280X Road racing history has many fascinating footnotes, most about "near success", and so it is for the very last BMW using a factory race chassis. Look no further than this American BMW that represents the glorious first steps that would lead to R90S domination in mid-1970s Superbike racing. BMW's participation in Superbike racing was part of a process of rejuvenation from staid to exciting. And so it was after the Adams family purchased BMW's US importers, New Jersey-based Butler & Smith, in 1971 and were faced with sluggish sales of the new R75/5, that company president Dr. Peter Adams created a five-year race program to refresh both his sales and the brand at large. Immediately he provided parts manager (and part-time racer), German-born, former NASA engineer, Udo Geitl, with resources to develop a Formula 750 R75/5 racer for AMA's 1972 National championship, run for the first time under F750 rules. With the help of BMW's American representative Volker Beer, Geitl obtained four factory-built race chassis identical to those used for the three works racers which Helmut Dähne, Dave Potter and Hans-Otto Butenuth rode in April 1972's F750 Imola 200; Dähne finishing 13th that year (and 14th on the same bike in 1973). But in fact, it was the first Geitl machine, built at Oscar Leibmann's Amol Precision, the Dumont, New Jersey BMW dealership, that saw action even before Imola, when Oscar's son Kurt failed to finish in the Daytona 100-mile Junior in March 1972. Geitl built up a second machine for Reg Pridmore who rode out of Butler & Smith's Californian operation, enlisting its service manager Helmut Kern to look after the bike. Kern, however, concluded that the R75/5 would be more competitive in the growing Production class and Pridmore's stunning run of 15 wins and six second places out of 23 starts in 1972/1973 proved him right. Back east, meanwhile, Geitl kept on developing the two factory-framed bikes and entered them in the 1973 Daytona 200 now clad in the same distinctive Wixom streamlining (now painted in B&S's red and white), that had been developed for the Harley-Davidson XR750-TT to compete with the then fast generation of fragile Japanese two-strokes. Liebmann and Pridmore were still outclassed on the Florida banking, even though Geitl's 92hp at the crank at 9,500 rpm was more horsepower than the factory chassis could handle. Geitl approached C&J Racing Frames asking them to construct their first-ever road racing chassis, broadly a copy of the factory frame, but now stiffer and lighter in chrome-moly tubing. But it still didn't fix the steering head flex caused by increasingly sticky tires. So after another wasted season, Kern convinced Adams to commission a pair of frames from Englishman Rob North, now in San Diego, creator of the successful BSA/Triumph 750 triples. The Rob North chassis mounted the motor higher still, with a longer swingarm to tame the wayward handling, and eventually Gietl extracted a claimed 98hp at 10,500rpm from the motor, which combined with a remarkable dry weight of 309lb - less than the big two-strokes - gave good acceleration and a top speed of 165mph. Pridmore retired from the 1974 200-miler, the new bike's debut, with a broken valve. But the new frame did allow Gary Fisher to qualify his BMW on the front row for the twisty 1975 Laguna Seca AMA National, alongside Kenny Roberts' factory Yamaha OW31. Battling for the lead the BMW's rear monoshock failed. This was a near glorious finale for the F750 Boxers. 1974 had seen the arrival of the new BMW R90S sportbike and Butler & Smith, with Geitl, went on to success. Another story, another time. Overnight B&S's F750 racers became yesterday's news. So when Washington DC-based sports photographer Wallace Henderson convinced Geitl to sell Leibmann's factory-framed bike identified by the massive 250mm Fontana 4LS drum brake on the bike in 1973 - Pridmore opted for twin stainless steel discs - on loan to Illinois BMW dealer Jim Cotherman for the 1974 Daytona 200; he paid a paltry $200. It then disappeared - Henderson doesn't appear to have raced it - and in 2006 he traded it straight up for a new R1200 GT with Daytona Beach BMW/Triumph/Ducati dealer Bill Perretti, a former rider with Team Obsolete. "I took on the BMW franchise in 2004, and coming from vintage racing, I always like to have the older bikes on display," says Bill. "One of my techs immediately knew what the bike was, I loved it." Perretti fully re-commissioned the engine by entrusting it to Memphis-based tuner Leo Goff. "I didn't want to restore the frame or bodywork, because it has the original paint and it's taken 40 years to get like that." Goff, a well-known Memphis blues bass player, former Norton twin drag racer and builder of many BMW motors says, "What Udo did to make this engine go fast was heroic, but an awful lot of the power came from the cylinder heads flowed by Jerry Branch, now missing from the engine. I aimed for a faithful reproduction of Udo's original. My last dyno run, we had 68hp at 9,000rpm at the rear wheel and 45 ft-lb of torque, which I feel represents pretty much where he'd got to with the R75/5 motor." Fortunately, the crankcase is the original to which Goff has fitted cylinders shortened by 10mm, or two fins, to provide two degrees of extra lean angle, aided further by installing 19-inch wheels front and rear. Special 82mm JE forged pistons were fitted via 10mm shorter Carrillo steel rods (titanium originally) to the engine's lightened and re-balanced stock, plain-bearing crankshaft, each carrying a heat-treated steel wristpin that's raised in the piston skirt to reduce engine width further via reduced deck height, combined with three narrower rings. Geitl also had machined weight off the flywheel, down to 3.3lb from the stock 7.9lb, for faster pickup and better handling with the shaft drive. And to eliminate oil cavitation, a hi-po oil pump is fitted, which uses just 3hp rather than the stock Eaton-type pump's 5hp. The motor has a 12.75:1 compression ratio, and the twin-plug, two-valve ported and flowed heads have 44mm inlet (42mm stock) and 38mm exhaust valves set at a 65-degree included angle installed, with dual coil springs, and operated via a Typ 336 camshaft driven by duplex chain. The original twin megaphone race exhaust has been refitted, but the Kröber electronic CDI Goff has been replaced with a Czech-made PAL magneto powered by a 12v battery mounted under the gearbox, firing two pairs of plugs via four separate Accel coils. Geitl's neatest trick has also been reproduced. The cylinder heads' intake ports have been re-angled by 15-degrees outwards, not only to give a straighter hit at the valves, but also to allow the 34mm Mikunis to breathe cooler air, and not have your legs interfere with the velocity stacks. This F750 racer features a stock R90S five-speed and clutch – Geitl installed a Heyser box but it proved too fragile and had disappeared long ago. The German-made tubular steel duplex cradle frame has a 28-degree head angle with the 35mm Ceriani forks set in Betor triple clamps. The 1450mm wheelbase is a big step up from the 1385mm of the street bike, presumably in pursuit of extra stability and the twin Koni shocks are heavily damped but relatively lightly sprung, with the rear 10in Hurst-Airheart steel disc brake with single-piston caliper matched by the handsome and effective 250mm Fontana 4LS drum. Total weight with oil but no gas is 348lb, says Perretti. I had the chance to ride the Leibmann bike for a handful of laps at the Barber track in Alabama, during the Vintage Festival meeting in October 2013. Leo Goff gets an A-plus rating for his work on recreating the Geitl-tuned engine with its extremely flat torque curve from the power threshold at 3,800 rpm to peak revs at 9,000 rpm. Get the Boxer engine chiming in the upper reaches of the tach and the result is a long-legged feeling of irresistible mix of momentum and exhaust blat. No getting away from it, though the BMW's handling needs an experienced rider for it's a meaty motorcycle. The ergonomics of the BMW are very individual, difficult for me, with a typically long stretch over the bare aluminum fuel tank to the quite steeply dropped clip-on 'bars. I was soon convinced I was pushing my luck by riding the BMW in anything approaching anger given that this was the bike's first time on a track in almost 40 years. The Liebmann, Butler & Smith F750 racer is surely significant, representing the last-ever factory BMW race chassis to be ridden in anger. A landmark motorcycle, part of a factory footnote that's both fascinating and a "near success".
Hier der Link mit vielen tollen Bildern:
http://www.bonhams.com/auctions/21389/lot/328/
Gruß
Alfons
1971 BMW F750 Butler & Smith Factory Racer Engine no. 001 298280X Road racing history has many fascinating footnotes, most about "near success", and so it is for the very last BMW using a factory race chassis. Look no further than this American BMW that represents the glorious first steps that would lead to R90S domination in mid-1970s Superbike racing. BMW's participation in Superbike racing was part of a process of rejuvenation from staid to exciting. And so it was after the Adams family purchased BMW's US importers, New Jersey-based Butler & Smith, in 1971 and were faced with sluggish sales of the new R75/5, that company president Dr. Peter Adams created a five-year race program to refresh both his sales and the brand at large. Immediately he provided parts manager (and part-time racer), German-born, former NASA engineer, Udo Geitl, with resources to develop a Formula 750 R75/5 racer for AMA's 1972 National championship, run for the first time under F750 rules. With the help of BMW's American representative Volker Beer, Geitl obtained four factory-built race chassis identical to those used for the three works racers which Helmut Dähne, Dave Potter and Hans-Otto Butenuth rode in April 1972's F750 Imola 200; Dähne finishing 13th that year (and 14th on the same bike in 1973). But in fact, it was the first Geitl machine, built at Oscar Leibmann's Amol Precision, the Dumont, New Jersey BMW dealership, that saw action even before Imola, when Oscar's son Kurt failed to finish in the Daytona 100-mile Junior in March 1972. Geitl built up a second machine for Reg Pridmore who rode out of Butler & Smith's Californian operation, enlisting its service manager Helmut Kern to look after the bike. Kern, however, concluded that the R75/5 would be more competitive in the growing Production class and Pridmore's stunning run of 15 wins and six second places out of 23 starts in 1972/1973 proved him right. Back east, meanwhile, Geitl kept on developing the two factory-framed bikes and entered them in the 1973 Daytona 200 now clad in the same distinctive Wixom streamlining (now painted in B&S's red and white), that had been developed for the Harley-Davidson XR750-TT to compete with the then fast generation of fragile Japanese two-strokes. Liebmann and Pridmore were still outclassed on the Florida banking, even though Geitl's 92hp at the crank at 9,500 rpm was more horsepower than the factory chassis could handle. Geitl approached C&J Racing Frames asking them to construct their first-ever road racing chassis, broadly a copy of the factory frame, but now stiffer and lighter in chrome-moly tubing. But it still didn't fix the steering head flex caused by increasingly sticky tires. So after another wasted season, Kern convinced Adams to commission a pair of frames from Englishman Rob North, now in San Diego, creator of the successful BSA/Triumph 750 triples. The Rob North chassis mounted the motor higher still, with a longer swingarm to tame the wayward handling, and eventually Gietl extracted a claimed 98hp at 10,500rpm from the motor, which combined with a remarkable dry weight of 309lb - less than the big two-strokes - gave good acceleration and a top speed of 165mph. Pridmore retired from the 1974 200-miler, the new bike's debut, with a broken valve. But the new frame did allow Gary Fisher to qualify his BMW on the front row for the twisty 1975 Laguna Seca AMA National, alongside Kenny Roberts' factory Yamaha OW31. Battling for the lead the BMW's rear monoshock failed. This was a near glorious finale for the F750 Boxers. 1974 had seen the arrival of the new BMW R90S sportbike and Butler & Smith, with Geitl, went on to success. Another story, another time. Overnight B&S's F750 racers became yesterday's news. So when Washington DC-based sports photographer Wallace Henderson convinced Geitl to sell Leibmann's factory-framed bike identified by the massive 250mm Fontana 4LS drum brake on the bike in 1973 - Pridmore opted for twin stainless steel discs - on loan to Illinois BMW dealer Jim Cotherman for the 1974 Daytona 200; he paid a paltry $200. It then disappeared - Henderson doesn't appear to have raced it - and in 2006 he traded it straight up for a new R1200 GT with Daytona Beach BMW/Triumph/Ducati dealer Bill Perretti, a former rider with Team Obsolete. "I took on the BMW franchise in 2004, and coming from vintage racing, I always like to have the older bikes on display," says Bill. "One of my techs immediately knew what the bike was, I loved it." Perretti fully re-commissioned the engine by entrusting it to Memphis-based tuner Leo Goff. "I didn't want to restore the frame or bodywork, because it has the original paint and it's taken 40 years to get like that." Goff, a well-known Memphis blues bass player, former Norton twin drag racer and builder of many BMW motors says, "What Udo did to make this engine go fast was heroic, but an awful lot of the power came from the cylinder heads flowed by Jerry Branch, now missing from the engine. I aimed for a faithful reproduction of Udo's original. My last dyno run, we had 68hp at 9,000rpm at the rear wheel and 45 ft-lb of torque, which I feel represents pretty much where he'd got to with the R75/5 motor." Fortunately, the crankcase is the original to which Goff has fitted cylinders shortened by 10mm, or two fins, to provide two degrees of extra lean angle, aided further by installing 19-inch wheels front and rear. Special 82mm JE forged pistons were fitted via 10mm shorter Carrillo steel rods (titanium originally) to the engine's lightened and re-balanced stock, plain-bearing crankshaft, each carrying a heat-treated steel wristpin that's raised in the piston skirt to reduce engine width further via reduced deck height, combined with three narrower rings. Geitl also had machined weight off the flywheel, down to 3.3lb from the stock 7.9lb, for faster pickup and better handling with the shaft drive. And to eliminate oil cavitation, a hi-po oil pump is fitted, which uses just 3hp rather than the stock Eaton-type pump's 5hp. The motor has a 12.75:1 compression ratio, and the twin-plug, two-valve ported and flowed heads have 44mm inlet (42mm stock) and 38mm exhaust valves set at a 65-degree included angle installed, with dual coil springs, and operated via a Typ 336 camshaft driven by duplex chain. The original twin megaphone race exhaust has been refitted, but the Kröber electronic CDI Goff has been replaced with a Czech-made PAL magneto powered by a 12v battery mounted under the gearbox, firing two pairs of plugs via four separate Accel coils. Geitl's neatest trick has also been reproduced. The cylinder heads' intake ports have been re-angled by 15-degrees outwards, not only to give a straighter hit at the valves, but also to allow the 34mm Mikunis to breathe cooler air, and not have your legs interfere with the velocity stacks. This F750 racer features a stock R90S five-speed and clutch – Geitl installed a Heyser box but it proved too fragile and had disappeared long ago. The German-made tubular steel duplex cradle frame has a 28-degree head angle with the 35mm Ceriani forks set in Betor triple clamps. The 1450mm wheelbase is a big step up from the 1385mm of the street bike, presumably in pursuit of extra stability and the twin Koni shocks are heavily damped but relatively lightly sprung, with the rear 10in Hurst-Airheart steel disc brake with single-piston caliper matched by the handsome and effective 250mm Fontana 4LS drum. Total weight with oil but no gas is 348lb, says Perretti. I had the chance to ride the Leibmann bike for a handful of laps at the Barber track in Alabama, during the Vintage Festival meeting in October 2013. Leo Goff gets an A-plus rating for his work on recreating the Geitl-tuned engine with its extremely flat torque curve from the power threshold at 3,800 rpm to peak revs at 9,000 rpm. Get the Boxer engine chiming in the upper reaches of the tach and the result is a long-legged feeling of irresistible mix of momentum and exhaust blat. No getting away from it, though the BMW's handling needs an experienced rider for it's a meaty motorcycle. The ergonomics of the BMW are very individual, difficult for me, with a typically long stretch over the bare aluminum fuel tank to the quite steeply dropped clip-on 'bars. I was soon convinced I was pushing my luck by riding the BMW in anything approaching anger given that this was the bike's first time on a track in almost 40 years. The Liebmann, Butler & Smith F750 racer is surely significant, representing the last-ever factory BMW race chassis to be ridden in anger. A landmark motorcycle, part of a factory footnote that's both fascinating and a "near success".
Hier der Link mit vielen tollen Bildern:
http://www.bonhams.com/auctions/21389/lot/328/
Gruß
Alfons