1982-1983 Honda V45 Magna

The Honda V45 Magna was the motorcycle everybody else was afraid Honda might build someday.

| May/June 2016

  • 1982-1983 Honda V45 Magna
    Motorcycle Classics archives
  • 1980-1983 Kawasaki KZ750 LTD
    Photo courtesy investment-bikes.com
  • 1982-1983 Yamaha 750 Maxim
    Photo courtesy investment-bikes.com

Honda V45 Magna
Years produced:
80.3hp @ 9,500rpm (claimed)
Top speed:
147mph (period test)
748cc liquid-cooled DOHC 16-valve 90-degree V4
6-speed, shaft final drive
518lb (w/half tank fuel)/45-50mpg
Price then/now:
$3,298 (1982)/$1,500-$3,000

By the end of the 1970s, every Big Four bike maker built a “Universal Japanese Motorcycle,” an across-the-frame inline four — the format Honda pioneered in 1969 with the CB750 Four.

Not surprisingly, Big Red threw down the gauntlet once more at the start of the 1980s with another technological tour de force, the 1982 V45 Sabre/Magna. Said Cycle magazine in its May 1982 issue: “This is the motorcycle everybody else was afraid Honda might build someday.” While the Sabre was meant to satisfy the sporting rider, it was the “custom” Magna that captured the zeitgeist. Upright riding, stepped seats and laid-back bars were the fashion, and the Magna checked all those boxes.

The 90-degree V4 engine used four overhead camshafts, each pair spun by a “silent” chain with automatic tensioner. The cams worked forked rockers to operate the 16 valves in pairs. Four 32mm Keihin CV carbs (two down draft and two side draft to suit the V4’s orientation in the frame) fed the cylinders. Pistons ran in steel liners driving a compact crankshaft with four main and two big end bearings, each journal supporting two connecting rods side by side and spaced at 360 degrees. Drive to the 6-speed transmission was by straight-cut gears, with the clutch sprocket made up of two narrow gears running side by side, one loaded by the clutch shock absorber. The result: gear lash — and therefore whine — was virtually eliminated.

Using four valves with a narrow included angle and “squish-band” combustion chambers offered greater intake efficiency and provided better detonation resistance so a higher compression ratio could be used for more power. Combined with a short stroke to allow more revs at lower piston speeds and liquid cooling to maintain optimum operating temperature, the 750cc engine produced more than 80 horsepower at 9,500rpm.

Praising the technical sophistication of the Magna, Kevin Cameron reported in Cycle that it “is the first to combine all these things into one compact, powerful sporting unit that truly fits the engine space of a motorcycle,” opining that “…Honda has once again redefined the motorcycle.” Cycle World made some interesting comparisons with Honda’s own air-cooled inline engine, noting that while the Magna produced just 5 horsepower more, it did so with a much fatter torque curve and would run on 86 octane gas, while the inline engine, an older design, required 92 or more.

The new engine powered the Magna to a 12.08-second standing quarter at over 108mph in the hands of Cycle World, although Cycle Guide’s Magna “devoured” two clutches in eight drag strip runs. Even so, Cycle Guide loved the engine: “Considerable torque is on hand from about 3,000rpm on up, and any shift point up to the Magna’s 10,000rpm redline can be used without bogging the engine.”

To get the look they wanted, Honda engineers employed a secondary 1-gallon gas tank under the seat, interconnected to the 2.7-gallon main tank and feeding fuel to the four carburetors via an electric pump. The rest of the bike was more conventional. The powertrain was rubber mounted into a dual-downtube full-cradle frame with an air-assisted conventional fork. Drive to the rear wheel was by a shaft inside the left side of the box section swingarm. Eighteen-inch front and 16-inch rear alloy wheels ran on 110/90 and 130/90 tires with dual 10.8-inch front disc brakes and, surprisingly, a 6.25-inch rear drum.

Cycle noted that the Magna’s low seat and forward pegs best suited shorter riders and also limited rear suspension travel. However, the soft springs and light damping also meant the Magna was “boulevard and freeway cushy.” Cycle World said it was slow steering and noted a tendency for the front end to run wide in fast corners, yet overall they said “the Magna maneuvers and handles well,” even while noting that “Driveshaft jacking is noticeable if you look for it.” Few testers liked the Magna’s ergonomics, with Cycle Guide saying that “the combination of pullback bar and forward footpegs turns a long haul on the Magna into just that: a long haul.” Cycle World perhaps summed it up best: “What we have in the Magna is a wonderful engine, an acceptable motorcycle and a hint of marvels to come.”

In his Cycle technical review, Cameron pointed to a potential weakness in the V45 engine — one that was to haunt Honda over the next few years. “The V45 carries its cams directly in the cylinder-head material … Haven’t there been failures of the cam-in-head material scheme, requiring expensive head replacements? Why are they still doing this?” Cameron went on to suggest this could be done effectively, but they were prophetic words, as Honda subsequently experienced cylinder head/camshaft wear issues with its V4s. That said, it’s worth noting that not all Magnas were so afflicted. Regular oil changes and avoiding overheating are key to ensuring longevity, and properly maintained, they seem to rack up miles with ease. MC

Contenders: Custom contenders to Honda’s V45 Magna

1982-1983 Yamaha 750 Maxim
Years produced:
86hp @ 9,000rpm claimed/128mph
748cc air-cooled DOHC inline four
5-speed, chain final drive
Price then/now:
$3,399 (1982)/$1,500-$3,000

The Maxim put a new emphasis on the custom class: comfort. With six-way adjustable handlebars and two-position footpegs, it was a cruiser you could actually tour on. “All bikes would benefit from some form of ergonomic adjustability, and every special-style bike needs it,” said Cycle.

Underneath the stepped seat, swooping gas tank and square headlight was essentially a 750 Seca with altered steering geometry and running an 18-inch front/16-inch rear cast alloy wheel combo. The engine was the Seca’s conventional 8-valve air-cooled inline four with a quartet of 32mm Hitachi CV carbs. Both the Seca and Maxim used Yamaha’s YICS induction control system to create swirl in the combustion chambers for improved combustion efficiency, and shim-over-bucket valves for easier adjustment. Five gears drove the drum-braked rear wheel by chain, while dual discs slowed the front hoop. A claimed 86 horsepower propelled the Maxim to 104.7mph in 12.62 seconds on the quarter-mile strip.

The Maxim’s softer suspension “provides a very compliant ride and also deals effectively with high-speed cornering,” said Cycle, summing up the Maxim as “one of the smoothest 750s around: it offers abundant, vibrationless 750-class power, a nice cruising ride, and good steering, stability and braking.”

1980-1983 Kawasaki KZ750 LTD
Years produced:
74hp @ 9,000rpm claimed/122mph (est.)
738cc air-cooled DOHC inline four
5-speed, chain final drive
Price then/now:
$2,849 (1981)/$1,500-$3,000

Kawasaki’s entry in the 750cc custom market was based on the KZ750, what Cycle World called “the fastest, toughest, meanest 750 ever to prowl a racetrack.” To get the custom look, Kawasaki fitted a smaller 16-inch rear wheel, stepped seat, a leading axle fork with altered geometry, softer suspension and high-and-wide handlebars. Cycle World liked the steering changes, finding the regular KZ750 “twitchy” and the LTD “one of the best handling semi-choppers available in the 750 class.” The downside, they said, was “tiller-like steering,” the result of too much pullback in the handlebars.

Underneath the 3.2-gallon gas tank, polished alloy replaced the regular 750’s blacked-out engine, but it was the same air-cooled, 2-valve, DOHC inline four with 34mm Keihin carburetors and a 5-speed transmission with chain final drive. Although weights between the standard KZ and LTD were similar, the LTD version added nearly half a second to the standing quarter at 12.62 seconds/104mph. The brakes were triple discs.

Cycle World, while admitting the KZ750 engine was “one of the most versatile and dependable engines available,” had some suggestions for improvement in the rest of the LTD: different handlebars, a larger gas tank and a seat with more padding.

5/3/2016 5:40:51 AM

The only way a V45 Magna will go 147mph is if you kicked it out of the Space Shuttle's cargo bay. My Maxim X would take a V45's lunch every day, and on a good day, it might crack 130.

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