Honda CM400A Hondamatic Profile
For some new riders, one of the more vexing things to learn about motorcycle riding is mastering the clutch and shifting process. Stalling the engine, missing shifts, and struggling to find neutral can add up to a very frustrating experience to the new would-be motorcyclist.
The answer would seem simple – some sort of automatic or at least clutchless transmission that eliminates all those problems.
In the mid 1970s, at least one major motorcycle manufacturer took a crack at solving the problem. In 1976, Honda introduced the CB750A Hondamatic — “A” standing for automatic.
Honda realized the 750 engine was a bit much for the entry-level Hondamatic, so it introduced the more beginner-friendly CB400A in 1978. The designation changed to CM400A in 1979, the displacement of the SOHC twin increased to 450 in 1982.
Why Honda chose “Hondamatic” as the name for their line of clutchless fluidic drive bikes is unclear — perhaps the “matic” part was thought to have more marketing appeal.
In any event, none of the Hondamatics had an automatic transmission. The transmission did eliminate the need for a clutch, but did not eliminate the need for manual shifting, though it did reduce it from five or six speeds to only two.
The CM400A has a two-speed fluidic drive that requires but two shifts to go from neutral to low and on to high gear. Power literally flows from the crankshaft to the transmission through a vane-type hydraulic torque converter.
When the rider shifts out of neutral, the bike stays in that gear until the rider chops the throttle and moves the foot shift lever to the next gear or back to neutral; the bike does not shift by itself.
The big difference between operation of the Hondamatic and a standard motorcycle transmission is that no clutch is necessary for shifting. At idle, the bike can be easily held in place by the rider, even when in gear.
The fluid in the fluidic drive system is the engine oil, not transmission fluid. A rotary vane pump on the crankshaft drives the oil through a stator that directs it over a pick-up vane on the output side, setting it in motion much the way wind flowing over a windmill will make it spin. As a result of this arrangement, there is no mechanical connection between the engine and transmission.
Since the motor oil has to work both to lubricate the engine and act as force transfer medium for the driveline, and the engine and transmission unit are air cooled, oil change intervals for the CM400A are amazingly short — only 1,875 miles between changes is recommended!
The engine was a bump up in displacement from the four stroke 356cc parallel twins of the 360 series it replaced, and it featured three valves per cylinder vs. two on the 360s and included a chain-driven counter balancer that the buzzy 360s lacked.
In 1981, the Hondamatics included both electric and kick starter—even though the kickstart lever had been dropped from most other models by that time. That had a practical reason: bump starting is not an option.
Riding a CM400A is about as easy as any full-size motorcycle could ever be — after a short warm-up, push in the choke, click the foot shifter up from neutral one spot and you’re in first gear.
The bike thrums quietly in place, with only a slight nudging sensation forward until you twist the throttle and it accelerates smoothly and amiably away.
At about 45 mph, cut the throttle and click the foot shifter up one more time and you’re in high gear, good for even freeway speeds. Acceleration is smooth, steady and moderate: period road tests put quarter-mile ETs just under 18 seconds with speeds in the quarter of only about 74 mph.
Downshifting is not really required, but does actually result in some degree of engine braking. Gear position can be kept track of—for those of us at the age where we can’t keep two gears straight—by using the colored lights in the instrument pod where a tachometer is usually located.
Fueling is handled by twin 28 mm Keihin constant velocity carburetors with built-in accelerator pumps that deliver between 48 and 50 miles per gallon economy.
Suspension included adjustable pre-load twin shocks to the rear and air-assisted front forks. A single piston caliper over single disc up front with a rod-activated drum unit on the back provides more than ample stopping power.
What sets the bike apart is the fact that it has a parking brake; necessary because even if left in gear, parked on an incline, the bike can roll.
The parking brake is set via a cable connected to the rear drum and is engaged by depressing a lock button on the left hand lever and squeezing the hand lever then releasing the button to lock the brake.
Setting the parking brake is deliberately a two-hand operation to simultaneously press the lock button and pull the lever, making it impossible to accidentally engage the parking brake while underway. This is a possibility, since the parking brake lever is where the clutch lever is on a conventional transmission bike.
There is also a parking brake warning light to prevent the rider from attempting to ride off with the brake applied.
By 1983, the Hondamatics were gone from the product line, but contemporary interest in automatic or clutchless shifting transmissions has re-emerged in recent years. Maybe the Hondamatics were way ahead of their time.
1981 Honda CM 400 A Hondamatic (pictured above) Specs:
- Engine: Air cooled SOHC parallel twin, 3 valves per cylinder, counterbalanced
- Displacement: 395 cc (24.1 in.3)
- Bore x stroke: 70.5 mm x 50.6 mm (2.78” x 1.99”)
- Compression rati:o 9.3: 1
- Carburetion: Two 28 mm Keihin constant velocity w/accelerator pump
- Transmission: 2 speed, clutchless hydraulic torque converter,#530 chain final drive
- Electrics: 12 v AC generator, .17 KW @ 5,000 RPM
- Frame: Steel tubing backbone, engine as structural member
- Front suspension: Telescopic air-assisted coil spring, oil damped
- Rear suspension: Twin shock swing arm
- Front brake: Single disc hydraulic 10.8”
- Rear brake: Foot activated single leading shoe drum
- Hand-lever activated parking brake
- Front tire: 3.50 S 18 tubeless, Comstar wheel
- Rear tire: 4.60 S 16 tubeless, Comstar wheel
- Wheelbase: 56.1” (1,425 mm)
- Seat height: 29.9”
- Weight (dry): 392 lb. (178 kg)
- Fuel capacity: 2.6 US gal. main, 0.4 US gal. reserve
Photos by Gary Ilminen