While many vintage motorcycles are defined by their speed, the Honda ST 70 DAX earned its legendary status through its unique T-bone frame engineering. Designed to resemble the long, low-slung profile of a Dachshund (hence the name ‘Dax’), the ST70 featured a revolutionary pressed-steel frame that integrated the fuel tank directly into the chassis, a design choice that maximized rigidity while maintaining a compact footprint for urban mobility.
| Parameter | Specification |
|---|---|
| Production Years | 1969 – 1994 |
| Engine Type | 72cc SOHC Single Cylinder Air-Cooled |
| Lubrication | SAE 10W-30 / 10W-40 (JASO MA) |
| Tire Size (F/R) | 3.50-10 4PR |
| Spark Plug | NGK C7HSA |
| Electrical System | 6V (Early) / 12V (Late) |
Engineering Overview
The Honda ST 70 DAX (ST70) is an exercise in functional minimalism. Powered by the incredibly reliable horizontal 72cc OHC engine, the DAX provided a middle ground between the smaller Z50 Monkey and full-sized motorcycles. Its semi-automatic 3-speed transmission (on most models) allowed for accessible riding, while the telescopic front forks and twin rear shocks provided a surprisingly compliant ride for such a small-diameter wheel setup.
Maintenance Essentials
Lubrication System
To maintain the longevity of the SOHC valvetrain, regular oil changes are critical. The ST70 utilizes a centrifugal oil filter system rather than a disposable paper element.
- Oil Grade: SAE 10W-30 or 10W-40 (JASO MA compliant).
- Capacity: 0.8 L total; 0.7 L during a standard exchange.
Chassis and Tires
The 10-inch wheels are sensitive to pressure fluctuations. Maintaining the correct PSI is vital for both handling and rim protection.
- Front: 1.25 bar (18 psi)
- Rear (Solo): 1.50 bar (21 psi)
- Rear (Dual): 2.0 bar (28 psi)
Electrical & Ignition
Depending on the production year, the ST70 may utilize a 6V or 12V system. Early models (pre-1980s) typically use the 6N2-2A-8 (6V) battery, while modern iterations and restorations often utilize the YTR4A-BS (12V). For ignition, the NGK C7HSA spark plug is the standard requirement, providing the correct heat range for the air-cooled cylinder head.
MotoSpecsLab Verdict
The Honda ST 70 DAX remains one of the most collectible ‘mini-bikes’ in history. Its combination of robust Honda engineering and iconic aesthetics makes it a favorite for restorers. From a technical standpoint, its simplicity is its greatest strength, requiring only basic tools and adherence to the specifications listed above to remain operational for decades.
Frequently Asked Questions
Q: How often should I change the oil?
A: For optimal performance, change the oil every 1,000 km (600 miles) or once a year, whichever comes first.
Q: Can I use synthetic oil?
A: Yes, provided it is JASO MA rated to ensure the wet clutch does not slip.