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1924 Mannequin 5 vs. 1925 Mannequin 6 Longstroke Sports activities
[Mar 24, 2008]
Since my 1925 Sunbeam Mannequin 6 Longstroke arrived two weeks in the past (March 2008), I’ve been curious to check its character to that of James Johnson’s 1924 Mannequin 5 touring mannequin. They’re each sidevalvers from the mid-20’s, with very comparable operating gear and mechanical configurations, from the identical esteemed producer; how totally different might they be?
1925 Mannequin 6 Longstroke Sports activities
The Longstroke was developed from Alec Bennett’s 1922 TT-winning (at 58.31mph) machine, and was initially often called the ‘Mannequin 6’. The ‘Longstroke’ identify was added for 1925, to what would have been the ‘Sports activities’ mannequin in that 12 months, however was known as the ‘TT Duplicate’ in 1923. How shortly issues modified in these important years between 1923-25, the place the Longstroke dropped in esteem from TT Duplicate to a ‘Sports activities’ mannequin in simply 2 years. That’s as a result of Sunbeam added a brand new overhead-valve engine to its line in 1924, the Mannequin 9 (and its variants), which sounded the dying knell to the sidevalve as a racing machine.
Surprisingly, even with the true benefits of the OHV engine, racers continued to develop the sidevalve for racing at occasions different than the Isle of Man TT; Brooklands, European races, trials, hillclimbs, and so forth. The truth is, though Bennett’s win in ’22 was the final for a sidevalver on the Island, they continued to achieve success for a few years in personal palms. Take for instance A.L. Loweth’s report of 94mph on a Norton 16H at Brooklands, in 1934! Supposedly ten years after the mannequin had develop into out of date for pace work. Meals for thought. I admit my very own bias in pondering sidevalve machines couldn’t be sporting, and would by no means fulfill a pace service provider corresponding to myself. Step by step, whereas investigating Sunbeam and Norton racing historical past, I got here to respect the common-or-garden flathead. And naturally, in america, Class C guidelines meant the flathead carried on racing via the Sixties, with its final variant, the 750cc Harley-Davidson KRTT, recording 150mph at Daytona in 1968!
1924 Mannequin 5 Touring
James bought his ’24 Mannequin 5 from British Solely Austria about two years in the past, and has spent appreciable time in his workshop, making the 84-year previous Sunbeam completely dependable. Now he feels assured in its mechanical soundness, and a number of other lengthy rides (together with one 800 miler!) have borne out his conviction that his Sunbeam may be ridden because the maker supposed.
The largest jobs he’s needed to deal with have been rewinding the magneto and changing a damaged steering stem; in any other case it’s been a matter of getting all the main points functioning easily (cables lubed and adjusted, clutch working correctly, brakes working, and so forth), which is de facto what ‘sorting it out’ means. It takes time to do these hundred small jobs in your off-work hours. That his bike runs so nicely is a testomony to James’ persistence.
By comparability, the Longstroke has simply began down the highway to ‘sorted’. Famous in a earlier weblog are my efforts to exchange hoses and faucets, get the clutch and carb working usually, and make footrests. The bike’s oiling could be very curious for a total-loss setup, as there is no such thing as a breather on the crankcase, however there IS an oil drain from the crankcase again to the oil pump – a semi-recirculating loop. The surplus oil appears to be burned off, because the bike smokes a bit, despite the fact that the oil pump feed is turned nicely down.
I haven’t discovered its high pace but, however I might estimate within the excessive 70mph vary. That’s going some for a motorbike which has little or no braking energy. The entrance drum is actually ineffective (each ‘Beams may be pushed ahead with the inverted lever absolutely squeezed), and the again brake is merely OK. James has relined his brakes, and suggests the rear brake ought to lock the wheel. Suspension motion from the Druid forks is minimal, and the springing could be very stiff. However, for all that, it’s a cracker! Because it weighs solely about 240lbs, it accelerates neatly, with robust engine pulses. The engine positively has a protracted stroke at 105.5mm(x77mm), however it revs pretty freely, and thrives on larger rpm than might sound probably – it has plonk at low rpm, however there’s a energy surge at round 3500 rpm at which the engine smooths out, and she or he actually begins to fly. The Longstroke engine feels barely skittish and revvy, and surprisingly excessive strung for a 20’s bike.
The dealing with could be very secure at pace, though when stationary, the entire bike appears very wobbly. In first gear, the entrance finish appears to ‘fall into’ corners, however as pace will increase (I’ve seen round 60mph up to now), cornering feels intuitive and takes much less effort. The handlebars are brazed in place and really low, with no adjustment doable, and you need to lean over the bike to succeed in the ‘bars. Clearly, you mould your self to this bike, not the opposite method round.
The Mannequin 5 has a totally totally different character; it’s a real gentleman’s machine, with a snug using place and mellow traits. With footboards and excessive, pulled-back handlebars, you’re seated within the traditional British ‘L’ using place. The place the gear selector on the Longstroke is stiff, the Mannequin 5 shifts softly and simply (particularly because the clutch releases absolutely). The facility band is constant and gradual, constructing pace with much less drama than the Longstroke, but by no means feeling sluggish, simply mannerly. The engine is sort of ‘sq.’ at 85x88mm, however the heavy flywheels preserve it from feeling like a short-stroke. One would possibly assume it retrograde so as to add 20mm to the stroke for a racing machine, however as they received the TT with this new long-stroke engine, they knew what they have been doing.
The dealing with on the ’24 feels persistently easy, with no change in really feel from low to excessive pace; I’m wondering if the using place has one thing to do with this? On the Lonstroke, my weight – which is simply 50lbs lower than the bike – is way additional ahead, shifting the bike’s heart of gravity in the direction of the entrance wheel. The Druid forks have softer springs, for a extra snug experience. The engines have a barely totally different head/barrel casting (seen within the photographs), and I of the would surmise that the Longstroke manages the next compression ratio (6:1?) than the Mannequin 5 (5:1?). Carb dimension is similar on each, with a choke of 1″. The sooner machine got here absolutely outfitted with acetylene lights entrance and rear (which work!), and a ‘little oil bathtub’ rear chaincase, a totally valanced entrance mudguard, a wider rear mudguard, and a baggage rack. James’ bike might be 20lbs heavier than mine, however I’m most likely 10lbs heavier than James, so the burden distinction is a wash.
Ultimately, each Sunbeams have super attraction, and are filled with the enchantment for which Sunbeams are well-known, as high quality merchandise that led the world in sporting occasions within the Twenties. They each operate amazingly nicely as bike right now,
On the finish of our check experience (or ‘shootout’ in moto-press communicate), I rolled out my 1928 TT90 Sunbeam for James to strive, for a REAL distinction. The three years between my Longstroke and the ’90’ are a lightyear in performance- with the later bike feeling, as James famous, ‘planted’ and secure, with about twice the facility of the sooner bike, and a four-speed gearbox as well. ‘We’re most likely the one individuals in North America to experience three Classic Sunbeams in a day’, stated James, and he’s most likely proper.
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