One of Honda’s longest-standing series is, without question, the Honda Z50 Mini Bike. Introduced in 1961 as the CZ100 in Tama Tech Park in Tokyo, this iconic pocket bike was initially sold in Europe before the U.S. and the first to spawn a market for commercial minibikes. Due to its massive success, it became the prototype for other iconic two-wheelers such as the CT70 and other dual-sport motorcycles.
The Honda Z50 is a 49-cc mini trail bike series produced from 1961 to 2017. More popularly known as the Gorilla or Monkey Bike, this two-wheeler preceded the Dachshund-like CT70 and led the minibike boom of the ’60s with its ultra-reliable air-cooled 4-stroke power mill.
In addition to a reputable engine, its overall design and build quality put it light years ahead of its lawnmower-powered counterparts. With its folding handlebars and 8-inch wheels, the Monkey Bike was convenient to transport or bring on outdoor adventures. Its small frame not only fit in a trailer home’s under-seat or an average-sized car’s trunk with ease but also forced a funny, simian crouch out of its riders.
Continue reading and learn more about this pocket bike that brings with it as much joy as it does nostalgia. And who knows? By the end of this guide, you may want to fit one of these classics in your garage, too.
History of the Monkey Bike
Despite the presence of repurposed lawnmower engines in the ’50s and minibikes being sold through dealerships as early as the late ’40s, it was not until the mass-production of the Honda Z series that all these became commonplace. That was how huge an impression the Honda Z50 lineup made on the riding community. And it all started in a company-owned tech park in Tokyo in 1961.
Head honchos saw the potential profitability of the wheeler outside amusement park tracks. So, after releasing a road-legal version in 1964 and redesigning a few elements, Honda launched the Z50 in Europe in 1968 and the U.S. in 1969. Expectedly, the launch happened in perfect timing with the minibike boom of the late ’60s.
The noticeable difference in technology between the Z50 series and its competition not only secured the mini bike’s standing on the riding map but also translated into sales of more than 70,000 units in its first year in the U.S. alone.
The Honda Z50 series had five model designations, namely – Z50M, Z50A, Z50R, Z50J, and ZB50. Out of the lot, the Z50J (released in Europe and other non-U.S. markets) had the longest run, followed by the Z50R series.
All generations of the Honda Z50 series were in production until 1999. But including iterations, these mini bikes were produced until 2017. For reference, here is a list of Z50 Mini Trail models released from 1964 until 1999:
| Year / ID | Colors | Retail/Trade-In Values |
|---|---|---|
| 1961 Z100 / 1963 CZ100 | Bright Red | N/A |
| 1967 – 1969 Honda Z50M | Candy Red, Bright Yellow | N/A |
| 1968 – 1969 Z50AK0 | $715 – $5,095 | |
| 1969 – 1970 Z50AK1 | Candy Red, Bright Yellow, Candy Blue | $680 – $3,300 |
| 1970 – 1971 Honda Z50A | Candy Ruby Red, Mexican Yellow, Candy Sapphire Blue | $680 – $3,300 |
| 1972 Z50AK3 | Candy Gold, Light Ruby Red | $565 – $2,335 |
| 1973 – 1999 Z50J | Candy Gold, Light Ruby Red (EU, Japan) | N/A |
| 1973 Z50AK4 | Hawaiian Blue Metallic, Candy Orange | $480 – $1,910 |
| 1974 Z50AK5 | Candy Sapphire Blue, Candy Topaz Orange | $480 – $1,910 |
| 1975 Z50AK6 | Candy Ruby Red | $475 – $1,880 |
| 1976 Z50A | Parakeet Yellow | $475 – $1,735 |
| 1977 – 1978 Honda Z50A | Tahitian Red | $475 – $1,880 |
| 1979 – 1981 Honda Z50R | $445 – $1,645 | |
| 1982 – 1985 Z50R | Blaze Red | $475 – $2,250 |
| 1986 Z50R | $590 – $1,955 | |
| 1986 Z50RD Special | Chrome | $1,540 – $9,385 |
| 1987 Z50R | Blaze Red | $475 – $1,645 |
| 1988 Z50R | $585 – $1,645 | |
| 1989 Z50R | $475 – $1,370 | |
| 1991 – 1995 Z50R | Shasta White | $235 – $1,570 |
| 1992 Honda Z50 Baja Monkey | White w/ Baja decals, handguards & twin headlights | $760 – $4,385 |
| 1992 – 1995 Z50RN/RP/R | Shasta White | $475 – $1,370 |
| 1996 – 1998 Z50R | $135 – $660 | |
| 1997 Z50RV | $155 – $660 | |
| 1998 Z50RW | $220 – $715 | |
| 1999 Z50RX | $230 – $735 |
Honda Z50 Specs and Features
Engine
The Honda Z50 Mini Trail is built around an air-cooled 49-cc power mill that the firm used on their 1963 CZ100 – the actual pocket bike that served as an attraction in the Tama Tech Park in Tokyo.
A 13-mm Keihin carburetor (view on Amazon) handles the air-fuel mixture for the bike. In 2008, this fuel system was replaced by Honda’s Programmed Fuel Injection (PGM-FI) system, which made for improved torque and power output of 3 hp/3.04 PS @ 7,500 RPM.
| Honda Z50A K2 (USA Type) | 1977 Honda Z50A | |
|---|---|---|
| Engine Type | 4-Stroke OHC | |
| Cylinder Layout | Single-cylinder, tilt up 10° from horizontal | |
| Carburetion System | Carburetion, 13-mm Keihin piston-valve type x 1 | |
| Engine Cooling | Air cooling | |
| Jetting | #50 (main); #100 (air); #38 (slow) | |
| Engine Fuel | Unleaded gasoline of at least PON 86 or RON 91, containing < 5% MTBE (Methyl Tertiary Butyl Ether), < 10% ethanol, or < 5% methanol w/ appropriate cosolvents and corrosion inhibitors | |
| Fuel Capacity | 2.5 L (0.7 US gal) | 4 L (1.1 US gal) |
| Bore x Stroke Ratio | 39 x 41.4 mm (1.53 x 1.63 in) | |
| Compression Ratio | 8.8:1 | |
| Displacement | 49 cm³ / 3 in³ | |
| Valve Stem to Guide Clearance | Intake: 0.01-0.03 mm (0.0004-0.0012 in) Exhaust: 0.03-0.05 mm (0.0012-0.0020 in) | |
| Valve Clearance Cold (Int/Ex) | 0.05 mm (0.002 in) | |
| Horsepower | 1.92 hp/1.95 PS @ 5,000 RPM | |
| Maximum Torque | 3 Nm (0.31 kgf-m, 2.2 ft-lb @ 4,200 RPM) | |
| Top Speed | 25 mph (40 km/h) | |
| Air Filtration | Oiled polyurethane foam type | |
| Lubrication | Pressure lubrication & wet sump | |
| Oil Filters | Centrifugal & screen mesh | |
| Engine Oil & Quantity | 0.8 L (1.7 US pint) of SAE 10W-40 Honda 4-stroke oil w/ an API grade of SJ+ meeting JASO T903 MA, MB standards Alternatives: SAE 30 (above 15° C/60° F); SAE 20W (-10° to 15° C/15°-60° F); SAE 10W (below 0° C/32° F) |
|
Drivetrain
The Honda Z series shares the same clutch assembly and gearshift pattern as the CT70. The main differences are in the front and rear sprockets, final drive, and transfer gear ratios. Driveline components remained unchanged during the first decade of the Z50 in production.
| Honda Z50A K2 (USA Type) | 1977 Honda Z50A | |
|---|---|---|
| Clutch | Wet, multiple disc, automatic, centrifugal type | |
| Transfer, Transmission Type | 3-speed constant mesh, manual | |
| Gearshift Pattern | N-1-2-3 (left foot operation) | |
| Drive System | Chain & sprocket final drive w/ 10-20 mm (0.040 – 0.080 in) slack (12T/37T); #415 (later #420) drive chain |
|
| Primary Reduction Ratio | 3.722 | |
| Final Drive Ratio | 2.917 | 3.083 |
| Transfer Gear Ratio | 1st – 3.182 / 2nd – 1.824 / 3rd – 1.190 | |
Ignition
Initially, the bike had a flywheel magneto ignition and an AC generator charging system – this later changed to a Capacitor Discharge Ignition for ’88 Monkey bike trims and onward, alongside electrical components upgraded from 6V to 12V.
Should you have an earlier Z50 model, you can avail a kit that would convert older points engine to current standards. Either that, or you can choose the easier route by installing a Chinese clone motor – brands Lifan, Zongshen, or GPX are favored by veteran mechanics.
| Honda Z50A K2 (USA Type) | 1977 Honda Z50A | |
|---|---|---|
| Ignition | Flywheel magneto | |
| Idle Speed | 1,200 – 1,300 RPM ± 100 | 1,500 RPM ± 100 |
| Starter System | Forward kick-start mechanism | |
| Spark Plug | NGK C6H or NIPPON DENSO U20FS, Gap: 0.6-0.7 mm (0.024 – 0.028 in) Torque specs: 1/2 to 3/4 turn past finger tight |
|
| Generator | Flywheel A.C. generator | |
| Battery | 6V (2 Ah)/10 HR, 12V YTR4A-BS format (recommended) | |
| Battery Dimensions (L x W x H) | 114 x 49 x 86 mm (4.50 x 1.94 x 3.38 in) | |
Tires & Brakes
The first Monkey bike had 89 × 127 mm (3.5 x 5.0 in) wheels. But later models, specifically the 1968 “High Bar” or “Slantguard” trims (the first units to be released in the U.S.), had 89 × 203 mm (3.5 x 8.0 in) wheels.
Brakes were expanding drums and did not turn into disc brakes until the Monkey R/RT series and the 2019 125-cc retro-styled iteration.
| Honda Z50A K2 (USA Type) | 1977 Honda Z50A | |
|---|---|---|
| Wheel Composition | Steel, laced wire spokes / Cast aluminum | |
| Front Tire, Air pressure | 3.50 x 8 (2 PR), 98 kPa (1.0 kgf/cm2, 14.2 psi) | 3.50 x 8 (2 PR or 4 PR), Bridgestone, Nitto, Inoue tire brands 98 kPa (1.0 kgf/cm2, 14.2 psi) |
| Rear Tire, Air pressure | ||
| Front Brake Type | 110-mm Internal expanding shoe | |
| Rear Brake Type | ||
Suspension
Initial models of the Honda Z50 Mini Trail had welded steel tubing with no rear suspension. As if a form of consolation, the small front fork offered very primitive wheel travel.
It was not until five years from entering the American market that the toy bike was equipped with a dual-shock rear suspension. This addition happened alongside a new frame, a new seat, and a redesigned fuel tank.
| Honda Z50A K2 (USA Type) | 1977 Honda Z50A | |
|---|---|---|
| Frame | Tubular steel | |
| Caster, Trail | 67°, 40 mm (1.6 in) | 65°, 42 mm (1.7 in) |
| Turning Circle | 2.6 m (8.6 ft) | |
| Wheelbase | 880 mm (34.7 in) | 895 mm (35.2 in) |
| Ground Clearance | 170 mm (6.7 in) | |
| Front Suspension Type, Travel | 26-mm Telescopic fork | |
| Rear Suspension Type, Travel | Rigid frame | |
Dimensions
Somewhat like the CT70, almost everything about the Honda Z50 dimensions was improved or upgraded for later-year models. The seat height was unchanged during the ’70s but had slight increases for succeeding trims.
Payload capacity remained the same throughout the vehicle’s production. Interestingly, the K2 trim is slightly heavier than units for general export, which weighed 49 Kg (108 lbs).
| Honda Z50A K2 (USA Type) | 1977 Honda Z50A | |
|---|---|---|
| Length | 1,280 mm (50.4 in) | 1,300 mm (51.2 in) |
| Width | 580 mm (22.8 in) | 615 mm (24.2 in) |
| Height | 865 mm (34.1 in) | 850 mm (33.5 in) |
| Seat Height (Unloaded) | 560 mm (22 in) | |
| Curb Weight | 53.5 Kg (118 lbs) | 53 Kg (117 lbs) |
| Vehicle Load Capacity Limit | 68 Kg (150 lbs) | |
Exterior
Both trademark features that separated the CT70 from its competition were derived from the Monkey bike. The Z50 was the first to have foldable handlebars. But instead of a Dachshund-like T-bone frame, it had a backbone-type chassis.
The 50-cc minibike eventually introduced a larger version with a 4-speed manual gearbox, larger fuel tank, twin-spar aluminum frame, and handlebars that did not fold down in Japan – the 1978 Z50J-III, fondly called the “Gorilla.” The Monkey R/RT series shared the same framework with the sportier but short-lived Gorilla.
| Honda Z50A K2 (USA Type) | 1977 Honda Z50A | |
|---|---|---|
| Headlight | 6V 15/15 W x 2 | |
| Brake/Taillight | 6V 17/5.3 W x 2 | |
| Indicator Lights | N/A | |
Cost of a Z50 Honda Mini Trail
The list price of the Honda Z50 ranged from $225 to $1,299. Meanwhile, the 2017 50th Anniversary Special Edition trim was valued at $3,999.
For secondhand units, Honda Mini Trail Z50 pricing falls between $550 and $10,00 – depending on whether the vehicle is fully restored, kept in mint condition with OEM components, or sold for parts.
Due to its age, used Z50s priced between $3,300 and $5,000 and in excellent working condition are already considered a steal. Any unit valued below $2,800 is most likely unrestored and may require some work to run.
Improvements Post-1970
Apart from the seminarian crouch that its riders naturally do while riding the bike, the Honda Z50 is also known for the number of cosmetic and mechanical upgrades it underwent. Here are some of those significant developments:
1972: A motorcycle-type swingarm with dual rear shocks was introduced on the bike, along with a chrome chain guard, brake pedal, and fenders.
1979: Redesigned fuel tank, newer seats, and BMX-style handlebars made the pocket bike more race-ready than previous models that catered to more casual rides.
1983: The recommended spark plug was changed to NGK CR6HSA, beginning with the ’83 model.
1984: Enhancements were made to its suspension system and vehicle dimensions. Dry weight slightly dropped while seat height increased by half an inch.
1986: Wheels were painted gold, and all steel parts were chrome plated for the Special Edition Z50RD trims.
1987: The frame, fenders, and shock springs were finished in Shasta White, and rims were painted gold.
1988: Ignition system of the Honda Z series changed from contact breaker to CDI. Additionally, the wiring harness changed from 6V to 12V.
1988: Honda released a sportier and more expensive street-legal ZB50, which came standard with a twin-spar aluminum frame and upward exhaust (view on Amazon) – alongside lighting improvements and other fixtures.
1996: The fuel tank logo was again redesigned with a new color palette of black, white, and red for ’96 – ’97 models.
While most of these upgrades kept the Monkey bike in production until 2017, some of them would have been better done at an earlier stage. For example, necessary changes to the Z50’s wiring harness were only done in 1988, leading to the classic wheeler being legally off the road for more than 20 years since its inception. Color options became fewer towards the later years of the mini bike, with all ’90s models being offered only in Shasta White.
End of Life for the Monkey Bike
The discontinuance of the Honda Z50 or Gorilla bike was a long time coming. Many speculate that Honda dropping the Z50A from its American lineup in 1978 may have started it. Others point to missing Honda Z50 parts and features like disc brakes and a true suspension. But in truth, it is the same reason that led to the halt of its successor – emission control regulations.
Unlike in larger motorcycles, it would be challenging for small-displacement engines to be emission-control compliant. Hence, the Japanese firm announced in March of 2017 that it would discontinue the Z50 series in August of that same year.
To end things on a high note, Honda retired the famous Monkey bike with the release of a 50th Anniversary Special Edition, sold for ¥432,000 (roughly $3,900) and only made available to Japanese consumers.
About Honda
Apart from being a pioneer of the ATV and motorcycle industry, Honda Motor Company Ltd. is also globally recognized for its uncanny ability to capitalize on emerging trends – like what it did with the Honda Z50 series. Merely 15 years from its inception, the Japanese firm created what will later go down as one of the greatest minibikes ever produced.
The Honda Z50 laid the framework for the famed CT70 and other pocket bikes and dual-sport motorcycles. Thanks to Honda’s ingenuity and efforts, consumers from all over the world continue to enjoy an armada of quality product offerings, ranging from multipurpose engines to high-caliber automobiles.
Conclusion – Honda Z50 Mini Bike Review
Unlike its successor, the CT70, the Honda Z50 is still very much in circulation – especially with the recent 2019 retro-styled iteration called “Monkey.”
While this latest model does incorporate elements from both the Z50 series and the 2014 Grom, it is very much reminiscent of the original Monkey Bike that both kids and adults enjoyed. It strikes a perfect balance between the casual and sporty nature of the two-wheeler and aptly fulfills many riders’ desires of how the Monkey Bike should be like.
Whether you go for this modern version or a well-kept 1969 trim, you are guaranteed an excellent riding experience – be it on pavement or off the road.
Kris is an avid off-roader and outdoor enthusiast who loves to brave the elements and take on challenging terrain. He also enjoys sharing his passion and knowledge with others so that they, too, can appreciate the ride.
About Kris