Bonhams Stafford Spring sale has been responsible for more sales of elite motorcycles than any other single sale anywhere in the world, rivaling even the combined January Las Vegas sales – it's that important. Not surprisingly, there are a number of very rare and valuable motorcycles going under the hammer on April 26, the most significant being a 1939 Vincent-HRD Series-A Rapide (US$320,000-380,000), an unraced 1979 Ducati 900 NCR Racer ($120,000-180,000), a 1926 Coventry Eagle Flying Eight ($120,000-180,000) and a 1930 Brough Superior 680 Black Alpine ($100,000-150,000).

Beyond the high ticket items though, the value toward the middle and lower end of this sale is quite astonishing. Unlike the far-more-buoyant car market where cars are worth millions and are regularly consigned to elite craftsmen who will charge a King's ransom for the work and that investment can be more than recouped, England has thousands of enthusiasts who spend thousands of hours restoring bikes, then sell them for pennies in the pound. Motorcycle enthusiasts are a different breed, and get as much enjoyment from the rebuild as they do from the riding.

Countless examples can be found at the just completed H&H Classic auctions sale, and countless more in the lots of the power-priced estimates at this sale. For $10,000 you can get a near perfect example of a bike you can have a load of fun on, and sell at the end of it all for more than you paid for it. The motorcycle marketplace has been undervalued for so long that despite some strong movement in the last few years (nearly half of the top 250 motorcycle prices ever paid have been paid in the last two years) it is still possible to buy a Laverda 750 SFC replica or a Silk 700 for (relatively) chump change. These bikes were pure exotica not long ago, and they are still purchasable for less than they were new, accounting for inflation.

Our task here however, is to look at the most sought-after motorcycles in the world, and Stafford has more than a sprinkling. The most exciting of all is this pre-war Vincent Rapide which is likely to take a spot in the top 20 of all time auction sales.

1939 Vincent-HRD Series-A Rapide

Estimate: £220,000 - 260,000 ($320,000 - 380,000)

This bike is world record material, as pre-war Vincent-HRD Rapides embody the joint properties of being very advanced technologically for the era, and made in very limited quantities. Opinions vary on how many were made but most agree the final tally was in the high seventies, being just a handful more than the equally sought-after Crocker V-twins being made across the pond at the same time. A few weeks ago, a Crocker set a record for the marque at the E.J. Cole Collection auction, and this bike too could set a new record for the illustrious Vincent marque.

Indeed, Vincents make up nearly 20 percent of our top 250 listing and the three most expensive Vincents of all-time to sell at auction are a 1948 Black Lightning ($375,303 – sold for £246,000), a 1939 Series-A Rapide ($366,775 – sold for £225,500) and another 1939 Series-A Rapide ($357,291 – sold for £198,400). Note: we calculate the exchange rates on the day of the sale here.

Completed in 2013, this was a most comprehensive restoration undertaken to concours standard, both mechanically and cosmetically. A measure of its quality may be gained from the painstaking approach taken to the use of stainless steel fastenings. Every nut, bolt, stud, washer and fitting has been reproduced in this material to as near original pattern as possible, being finished in one of three ways: polished to simulate a chromed finish; dull blasted to simulate cadmium; or chemically blackened to simulate a Parkerized finish. The result is a finish that has the same appearance as the original but with the enduring qualities of stainless steel. The paintwork is all traditional stove enamel.

Expect some serious bidding action over this machine. Very exciting!

1979 Ducati 900 NCR Racer

Estimate: £80,000 - 120,000 ($120,000 - 180,000)

The Ducati NCR of 1978 was the bike Mike Hailwood made his legendary comeback on, returning to the Isle of Man Mountain Circuit to win the Formula One race after an 11-year self-imposed exile from mainstream motorcycle racing at the geriatric (at least in racing terms) age of 38 years.

Located close to the Ducati factory in the Borgo Panigale district of Bologna, Italy's NCR was Ducati's original, albeit external, racing department and in 1978, NCR produced a small batch of 25 machines for homologation purposes for the Formula 1 class of the 1978 Formula TT World Championships – the championship is now defunct, having largely been replaced by the World Superbike Championships in 1990.

One of that original batch of 25 was purchased in 1978 and stored, untouched, until in early 2014, it sold at auction for $175,500 and is accordingly one of a very few modern motorcycles to have appreciated in value to Top 100 status. Another of the original batch sold in Las Vegas in January, 2014 for $69,000, while another 1979 model (with a square case engine?) sold at Quail Lodge in 2011 for $52,650. Obviously, Bonhams estimate his purposefully wide to account for the varied history of sales of these rare machines.

The NCR Ducati for sale here is one of only five manufactured for the 1979 season using the "round case" engine with an 88 mm bore and 74.4 mm stroke for a displacement of 905 cc. The frame and engine are the original pairing as confirmed by an accompanying document of authentication.

The bike has had only two owners, both collectors, and the engine has been taken apart only once, by a German Ducati expert to determine its originality and condition, the process being extensively documented with numerous photographs. The professional consulting engineer's signed report (dated February 17, 2015) is on file together with other paperwork relating to its earlier history. Described as "mint" condition, this NCR is an unmolested example of a significant historic racing motorcycle.

1926 Coventry Eagle Flying Eight

"There is an undeniable fascination in owning a machine capable of seemingly illimitable speed. For ordinary running the engine is merely idling, 50 mph seems like 30 mph on most machines, 60 mph is a comfortable touring speed, while when one of those very rare stretches of really safe road is encountered the speedometer needle will, when the throttle is opened wide, pass the 80 mph before remaining steady." Road test of a Coventry Eagle Flying Eight in Motor Cycling, 4 November, 1925.

Estimate: £80,000 - 120,000 ($120,000 - 180,000)
Key points: 980 cc V-twin

Two very similar machines to this have previously appeared at Bonhams auctions and they have both sold for stratospheric prices. At this same Stafford Spring Sale eight years ago, a 1928 Coventry-Eagle Flying-8 sold for £100,500 ($194,739) and another 1928 Coventry-Eagle Flying-8 sold for $265,500 at Quail Lodge (Pebble Beach) in August, 2011.

Both bikes contained the 980 cc OHV KTOR engine, just as this bike has and just as Brough Superior SS100 machines did at that time. The similarities between the Brough Superior and Coventry Eagle Flying Eight are many, with the Coventry firm's Percy Mayo and George Brough having become acquainted while on active service during WWI. Percy was the son of Coventry Eagle's founder, Edmund Mayo and George Brough and he had based their friendship upon their similar taste in motorcycles.

The bike for sale has been in the vendor's ownership for 28 years and is offered with a most substantial history file containing an old-style continuation logbook (issued 1945), expired MoTs, an original Coventry Eagle instruction book and range brochure (1924), restoration and maintenance notes, sketches, photocopied literature, press cuttings, photographs, invoices, correspondence, etc.

The following lot to the above at the Stafford sale is a 1924 Coventry Eagle Flying Eight "project" which came from the same estate. The dismantled Flying Eight is a side-valve version and comes with two sidevalve engines (one a desirable four-cam), and is expected to sell for £12,000 - 16,000 ($18,000 - 23,000).

1930 Brough Superior 680 Black Alpine

Estimate: £70,000 - 100,000 ($100,000 - 150,000)

The history of this wonderfully patinated Black Alpine is known from new, including starring with such luminaries as Wallace & Grommit on Channel 4's Big Breakfast in 1996. A matching numbers machine, it comes with a large history file including photographs, a Brough Superior club copy of the original works record card, contemporary magazine reports of the new Black Alpine, a separate notebook recording work on the machine over many years, a 1937 letter from George Brough to the then owner, an 2012 article written for the Brough Superior Club newsletter, a 1996 roadtest of the machine by Motorcycle Sport and Leisure, a photocopy of a two page chapter about the machine from Titch Allen's Brough book Legends in their Lifetime, two continuation logbooks, ad infinitum.

1937 Brough Superior 11-50

Estimate: £30,000 - 40,000 ($ 44,000 - 59,000)

Launched in 1933, the 1,096 cc sidevalve 11-50 was the largest capacity Brough Superior to enter series production, sitting between the SS80 touring and SS100 super-sports models. The 11-50 was a long-legged, effortless tourer and could exceed 90 mph (145 km/h) in solo form or pull a heavy sidecar at up to 75 mph (120 km/h). Production lasted until 1939, by which time the 11-50 was the only JAP-powered machine in the Brough Superior range.

This particular matching-numbers machine was displayed on the Brough Superior stand at what was then the most important motorcycle show in the world, the Earls Court Motorcycle Show, in September 1937. A sprung frame model, it also came equipped with a separate oil tank, foot gear control, small pannier bags ("show type"), Cranford hinged rear mudguard, top and bottom rear chain cases, rear footrests, and Amal touring handlebars complete with dual integral twist grips.

1928 Indian 401 Four

Estimate: £65,000 - 70,000 ($95,000 - 100,000)

This rare Indian 401 has an unknown history prior to being smuggled out of Czechoslovakia before the Berlin Wall came down, and purchased by the vendor in 1988. The machine was in a very poor state and has undergone a complete restoration. An Indian Model 401 sold at Scottsdale earlier this year for $104,500.

1955 Vincent Black Shadow Series-D

Estimate: £40,000 - 50,000 ($59,000 - 73,000)

One of only 141 un-enclosed Series-D Black Shadows made, this 1955 model has a complete history of its total of 53,730 miles since new.

1955 Vincent Black Shadow Series-D with Black Prince Bodywork

Estimate: £40,000 - 50,000 ($59,000 - 73,000)

Still in the hands of its original owner, this Black Shadow with Prince bodywork had an engine rebuild 15 years ago and has been stored since 2003. The machine has been upgraded, boasting 12-volt alternator electrics, electronic ignition, flashing indicators, "crash" bars, panniers and modern mirrors. The machine has covered only a handful of miles in the last 20 years with a current odometer reading of 37,119 miles.

1953 MV Agusta 125 Monoalbero Racer

Estimate: £25,000 - 35,000 ($37,000 - 51,000)

MV Agusta won its first World Championship in 1952 with Cecil Sandford in the saddle. In 1953, the company offered an over-the-counter racer for privateers. Italian regulations for the domestic "Formula Sport" stipulated that machines should have only a single camshaft (monoalbero) and the 125 production racer employed a train of gears to drive its SOHC.

With measurements of 53x56 mm and a 27 mm Dell'Orto racing carburettor, the motor produced 16 bhp at 10,300 rpm and had a top speed of over 90 mph. The cycle parts were an exact copy of the 1952 works bikes, featuring a tubular duplex loop frame, telescopic front fork with central hydraulic damper, and swinging-arm rear suspension. Brakes were full-width aluminum-alloy: 7-inch diameter at the front, 6-inch at the rear. Dry weight was 165 lb (75 kg).

Because Italy's long-distance road races, such as the Moto Giro d'Italia and Milan-Taranto, required that machines be street legal and possess lights, a flywheel generator formed part of the specification. The MV Agusta monoalbero 125 racer proved an enormous success, remaining in production until 1956 and continuing to offer privateers a competitive ride in the 125 cc class for many years thereafter.

The current vendor, a prominent German collector, purchased this MV from a German racer, who had acquired it from Giancarlo Morbidelli, founder of the eponymous motorcycle company and head of the Morbidelli Museum. Believed restored in the Morbidelli workshops, the machine runs very well and was last used in September 2014 at Dieburg.

1957 F.B. Mondial 175 Bialbero Racer

Estimate: £35,000 - 45,000 ($51,000 - 66,000)

This 1957 F.B. Mondial 175 cc Bialbero Racing Motorcycle would have been bleeding edge at the time of its construction, with the company having won both the 125 and 250 world titles in 1957. It was purchased by the vendor from the famed George Beale around 15 years ago having been restored a few years previously.

1972 Laverda 750SFC Replica

Estimate: £13,000 - 16,000 ($19,000 - 23,000)

Only 549 Laverda 750SFC production racers were built, but they gained a reputation for reliability and speed, dominating international endurance races in 1971. dominating the international endurance race circuit in 1971. The SFC featured in the Guggenheim Museum's famous "The Art of the Motorcycle" exhibit and is unquestionably one of the most iconic bikes of the seventies. As it was closely based on the 750 twin, replicas are plentiful, but nonetheless sought after.

1982 Yamaha TZ500J GP Racer

Estimate: £20,000 - 25,000 ($29,000 - 37,000)

This TZ500J was raced extensively in the Far East during the 1980s, mainly by the Malaysian rider Fabian Looi, who used it to win the Penang Grand Prix in 1983, '86 and '87, while Australian rider Brent Jones rode it to another Penang GP win in 1988 (a full list of race results is available). The machine was purchased in Australia in 1997 and is presented in "as last raced" condition.

1930 Harley-Davidson 74ci VL Big Twin

Estimate: £12,000 - 16,000 ($18,000 - 23,000)

Restored around a decade ago, the history of this bike is largely lost, and although appearing authentic, it is sold strictly as viewed.

1927 Ace 1,229 cc Four

Estimate: £18,000 - 24,000 ($26,000 - 35,000)

The Ace Four is a highly desirable motorcycle and examples rarely come to auction, the most recent example selling as part of the EJ Cole Collection for $126,500. This example is believed to have resided in the USA before being sold to the vendor in 2005. Little else is known about the Ace's history or condition. Sold strictly as viewed.

1927 Cleveland 750 4-45 Four

Estimate: £25,000 - 35,000 ($37,000 - 51,000)

Bought as a "basket case" from a California dealer, this rare Cleveland 4-45 Four was first registered in the UK in 2004. The vendor is its only recorded owner and it is believed that Harley-Davidson and Indian parts were used in its restoration.

1927 Excelsior 750 Super-X

Estimate: £15,000 - 18,000 ($22,000 - 26,000)

Introduced to the US market in 1925, the Super-X retained the Big Twin's F-head valve gear while reverting to the leading-link front fork used on its earliest ancestors. Elsewhere though, it was extensively redesigned, featuring unitary construction of the engine/gearbox and geared primary drive encased with an alloy casting. There was a higher-performance Super Sport model available and this pair of Super-Xs continued with few changes until motorcycle production ceased in 1931. First registered in the UK in 1951, this Excelsior Super-X was purchased by the current vendor in 1985.

1925 Henderson 1300 De Luxe Four

Estimate: £30,000 - 36,000 ($44,000 - 53,000)

This 1925 Henderson 1300 De Luxe Four was purchased from Canada in 1988 and first registered to the late owner in April 1991 having been purchased at the Allington Castle auction in April 1990. Since then the Henderson has participated in the Oude Klepper Glorie event in Belgium (1993) and the 2014 Banbury Run.

1946 Norton 500 Manx Racer

Estimate: £10,000 - 14,000 ($15,000 - 20,000)

This "garden gate" Manx was first road registered in 1987 and has been rebuilt with new main and big-end bearings, a Carrillo con-rod, and new piston, valves and guides. If the stampings are correct, this motorcycle was originally built as a Model 40 (350 cc) Manx, while the engine number indicates the engine is a 490 cc (Model 30) unit dating from 1950.

1955 Vincent Rapide Series-D

Estimate: £30,000 - 36,000 ($44,000 - 53,000)

This 1955 Vincent Rapide Series-D was red when acquired and no evidence of black paint has been found beneath the red, suggesting that this motorcycle may be one of those Vincents periodically produced in small batches finished in this non-traditional color scheme, mainly for the North American market. Noteworthy features of this particular machine include an Alton 12-volt generator, Grosset electric starter, electronic ignition and a Dave Hills center stand (original stand included).

1926 Scott 500 TT Racer

Estimate: £14,000 - 18,000 ($20,000 - 26,000)

It seems unfair that such a significant motorcycle could sell for seemingly so little, if the estimate proves accurate. This bike is one of the three factory Scott 500 race bikes prepared for the 1926 Isle of Man TT races. Not only that, the bike was essentially a prototype for the new Flying Squirrel which was launched at the Olympia Motorcycle Show later that year. The whole story is on the auction page. Exceptional provenance for such little money.

1933 Brough Superior 11-50HP Project

Estimate: £10,000 - 12,000 ($15,000 - 18,000)

Though this 1933 Brough Superior 11-50HP is a restoration project, it is an ideal candidate, with most of its original equipment still present.

1968 Velocette 500 Venom Thruxton

Estimate: £13,000 - 16,000 ($19,000 - 23,000)

First produced in 1955, a production Velocette Venom set a motorcycle world record for 24-hours with an average speed of 100.05 mph (161.01 km/h) in 1961, becoming the first motorcycle of any capacity to break the "ton" over 24 hours. In 1964, an optional high-performance cylinder head was made available and a Venom equipped with the new head won its class in the 1964 Thruxton 500-mile race.

The new cylinder head was then fitted to the new model named after the race victory and shown for the first time at the 1964 Earls Court Show, claiming 41 horsepower. This matching-numbers Thruxton Venom Velocette was for a time the ultimate café racer, and it is believed that between 1,100 and 1,200 were produced.

1977 Silk 700S Mk 2 (with factory 500 motor)

Estimate: £5,500 - 7,500 ($8,000 - 11,000)

Part of a deceased estate, this ultra-rare two-stroke twin Silk is one of only 138 built during the marque's six-year lifespan. Following delivery, the Silk was used extensively in competition, eventually resulting in George Silk providing what is believed to be one of only two special 500 cc short-stroke engines built by Silk. This short-stroke motor remains in it to this day. Used in competition, the new engine was believed to produce more power with less vibration at high revs.

1972 Triumph 750 X75 Hurricane

Estimate: £15,000 - 19,000 ($22,000 - 28,000)

BSA-Triumph's most iconic post-WWII motorcycle and the product of a comedy of errors which conspired to limit its production run and make it valuable too. Faced with the onslaught of much faster, much much more reliable, oil-leak-free motorcycles with modern styling from Japan, the company produced yet another 750 with vertically-split crankcases and pushrod valve actuation, albeit with three cylinders instead of two.

The marketing-aware distributors in America knew better and commissioned designer Craig Vetter to create a customized BSA Rocket 3. BSA hated it, but when the bike appeared on the cover of Cycle World in 1970, and massive public interest demanded it, the company was lucky enough to have enough sets of inclined-cylinder BSA crankcases left for a limited run of 1,200 bikes under the Triumph badge, as BSA had gone bankrupt. It took Vetter two years to get paid. The limited edition Hurricane is now the most valuable post-WWII British motorcycle.

1920 Indian 7 hp Powerplus

Estimate: £16,000 - 20,000 ($23,000 - 29,000

Developed to compete with Harley-Davidson 61ci (1,000 cc) v-twin is deserving of its "Powerplus" name. Found on a farm in New Zealand in 1969, the reconditioned bike went on to have an active life, participating in many events in New Zealand and Australia. Re-commissioned to UK roadworthiness standard in 2014, the Indian is described as a thoroughly reliable, well-sorted and capable rally bike.

1938 Ariel Square Four 1000

Estimate: £15,000 - 18,000 ($22,000 - 26,000)

The Ariel Square Four was one of the first designs of a young Edward Turner, who went on to design the Triumph Speed Twin, Thunderbird, Tiger and Bonneville and the Daimler V8 before eventually becoming the Chief Executive of BSA Group (including BSA, Ariel, Triumph and Daimler).

The first Ariel Square Four 4F displaced 500 cc and was released at the 1930 Olympia Motorcycle Show, raising to 601 cc in 1932 as the 4F and 995 cc in 1936 as the 4G.

The 1,000 cc 4G was an entirely new Turner design with duralumin pushrod operated valve gear, vertically split crankcases with dry sump oiling, one piece crankshafts, light alloy conrods, white metal plain bearings, and a rear mounted Solex carburetor.

This particular 1,000 cc 1938 Ariel Square Four was awarded one of the concours world's ultimate accolades when it scooped first prize in the Louis Vuitton Classic Concours at the Hurlingham Club in 1999. In 2008 it won the Square Four category at the Ariel Owners Club annual rally concours.

Indeed, the Ariel Square Four is one of those famous classic motorcycles that were so popular and plentiful, that their price has remained well within the reach of any enthusiast. Apart from the £15,000+ concours-winning Squariel, the Stafford sale contains another four Square Fours of different vintage and price estimates.

From top left and clockwise above, there's another pre-WWII Ariel being a 1936 601 cc Model 6F (£12,000 - 16,000, $18,000 - 23,000). Then there are three post-WWII bikes including a 1951 995 cc 4G Mk I (£8,000 - 12,000, $12,000 - 18,000), a 1952 995 cc 4G Mk I (£8,000 - 12,000, $12,000 - 18,000) and a 1958 995 cc 4G Mk II (£7,000 - 10,000, $10,000 - 15,000). The 1958 model in particular represents exceptional value in that it has done just four miles since a total restoration.

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