Years produced: 1968-1975
Claimed power: 3hp @ 7,500rpm
Top speed: 30mph
Engine: 49cc air-cooled SOHC single, 39mm x 41.4mm
Weight: 128lb (58kg)
Price then/now: $239/$2,000-$5,500
No one who stopped by the motorcycle auctions in Las Vegas this past January could have failed to notice the large number of minibikes for sale. Most were Hondas, and many of those were from the Northwest 100 Collection based at the LeMay automobile museum in Tacoma, Washington.
Of course, homemade minibikes have been around since the first creative gearhead attached a lawnmower motor to a kids’ bike. But it was the special transportation needs of wartime that inspired a production minibike.
The Welbike was designed in World War II specifically for battlefield communications and transport. It used a 98cc Villiers 2-stroke engine in a rigid frame with a retractable seat and folding handlebars. With a full gas tank, it was packed into a metal drop canister and parachuted to the battlefield alongside paratroops. Welbikes were mainly used by Britain’s Special Operations Executive units in Europe but were also used by U.S. forces in the Korean war.
Developed from the Welbike, the civilian Corgi minibike was built from 1948-1954 by Brockhouse Engineering in England, and sold in the U.S. as the Indian Papoose. By the time production ended in 1954, more than 27,000 had been built.
Minibike kits were widely available through the 1960s by mail order, of course — you just added your own engine, usually a Tecumseh or Briggs & Stratton. Or you could buy one ready built like the Doodle Bug from Fox Engineering or the John Steen-designed Taco. But these were still very crude machines, with little or no suspension and lacking street equipment.
Honda launched its first minibike (quickly named “Monkey Bike”), the relatively basic and simple Z100 in 1961 — but in Europe only. The Z50M of 1967 introduced folding handlebars and seat, and an OHC engine, but still lacked rear suspension and lighting.
It wasn’t until 1968 that the definitive Honda minibike arrived in the U.S.: the Z50A-K0 “hardtail,” sometimes also known as the “high bar” or “slantguard” (describing the folding handlebars and fender). It was built around the ubiquitous 49cc SOHC 4-stroke engine from the C100 Cub, together with its 3-speed semi-automatic transmission. As well as the sophisticated powerplant, the Z50A featured telescopic front suspension, 3.5 x 8-inch tires, and internally expanding drum brakes front and rear.
For 1969, the K1 added street-legal lighting. Lower handlebars were fitted on the 1969/70 K1 “short tail” and the 1970/71 K2 “long tail.” Reports of frame breakages led to the introduction of swinging arm rear suspension on the 1972 Z50A, renamed as the Z50J “soft tail,” which remained on the American market until 1978, when it was replaced by the more dirt-track-oriented Z50R.
U.K. magazine Motorcycle.net took a “soft tail” Z50A for a spin. Their tester found it “difficult, at first, to take the whole concept seriously,” and, not surprisingly, the seating position felt “cramped and awkward.”
The tester found the semi-automatic gearshift was “hard to get right,” because the clutch disengaged with every depression of the shift lever. And while the engine was described as sluggish, it was powerful enough that shifting quickly at low speed risked “the whole show going vertical.”
Once underway, though, the ride was “secure” and the handling “controllable,” though the tester found the chassis getting “more than a shade wobbly” at speed. Stopping “can be a fraught affair too, especially once up at the bike’s top speed around 30mph.” The tester recommended riders to “adjust your thinking distances, just in case.”
Motorcycle.net concluded: “The one overriding feature of the Monkey has to be the fun of riding one; you can’t go fast, but you can have a whale of a time getting around, and you certainly do attract some considerable attention as you ride though towns and stop at traffic lights. It isn’t hard to see why the monkey was so popular back in the ’60s and it must have rivalled the Italian scooter in its practicality and novelty value too.” MC
Contenders: Mini bike alternatives to the Honda Z50
1968-1973 Benelli Dynamo
- 4.5hp @ 7,800rpm/33mph
- 49cc (59.3cc 1970-on) air-cooled, 2-stroke single, 40 x 39mm (44 x 39mm)
- 130lb (59kg)
- $500-$3,000 now
The Benelli Dynamo Trail and Compact were manufactured in Pesaro, Italy, imported into the U.S. by Cosmopolitan Motors, and sold initially through J.C. Penney. Both models used a 50cc (59cc from 1970) 2-stroke single-cylinder engine with a 4-speed foot-shift transmission and high-level exhaust.
Both models used a spine frame with front telescopic and rear swinging arm suspension. The Trail was fitted with 3.0 x 10-inch wheels, knobby tires, an engine bash plate, and was geared lower with a large rear drive sprocket. The on-road Compact wore 3.5 x 8-inch street tires. Both came fully street-legal with a horn, a speedometer and a lighting kit. Cosmopolitan claimed the Dynamo Trail version could cover all types of terrain with two passengers. A third version for offroad use only was also available from 1970-1972, lacking the speedo and electrical accessories.
The Dynamo 2 arrived for 1972 with cosmetic changes that blended the seat and gas tank more closely.
The last year for the Compact was 1972, while restrictions on the sale of 2-stroke motorcycles in the U.S. meant the last year for the Dynamo Trail was 1977.
1971-1973 Suzuki MT50J Trailhopper
- 3hp @ 6,000rpm/30-35mph
- 49cc air-cooled, reed-valve 2-stroke single, 41mm x 38mm
- 132lb (60kg)
- $500-$2,500 now
No doubt aiming for a slice of Honda’s Monkey Bike sales, the MT50J Trailhopper was similar in size and specification to the Z50J with folding handlebars, full suspension, expanding shoe drum brakes, street lighting and electrical equipment, and trail-style 8-inch tires.
Seat and handlebar height were also adjustable. Its angular bodywork may not have been to everyone’s taste, but its economy certainly would have been: filling the 0.65-gallon gas tank at the time cost about “a quarter.”
The 3-horsepower 2-stroke engine’s efficiency was helped by a reed valve in the intake, and the 3-speed transmission featured a centrifugal clutch, so the rear brake was operated from the handlebar where the clutch lever would have been. Engine lubrication was automatic, and the muffler wore a spark arrestor as stock.
But the Trailhopper fell victim to Honda’s dominance of the minibike market, and though it could be had for less money, that didn’t make enough difference. The MT50 was dropped in the U.S. in 1973.
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