Woods Metal: 1966-1979 Honda CT90

Comparing the Honda CT90 with its primary competitors, the Kawasaki J1TR/TRL 80 and Yamaha YG-T80 Trailmaster.

| September/October 2018

  • honda ct90
    Honda CT90.
    Photo courtesy Honda
  • kawasaki j1tr
    1966-1967 Kawasaki J1TR/TRL 80.
    Photo courtesy Kawasaki
  • yamaha yg t80
    1964-1969 Yamaha YG-T80 Trailmaster.
    Photo courtesy Yamaha

  • honda ct90
  • kawasaki j1tr
  • yamaha yg t80

Honda CT90

  • Years produced: 1966-1979
  • Power: 7hp @ 8,500rpm (claimed)
  • Top speed: 60mph
  • Engine type: 89.5cc (50mm x 45.6mm) air-cooled OHC single
  • Transmission: 4-speed semi-auto, chain final drive
  • Weight/MPG: 179lb (dry)/80-90mpg (period test)
  • Price then/now: $275 (1966, est.)/$800-$2,000

The enduring appeal of Honda's small off-highway motorcycles stems from two factors: America's passion for playing in the dirt; and the remarkable versatility of the Honda Cub.

The story goes that in 1960, a single Honda shop in Boise, Idaho, was selling more Cubs than the entire dealer network in the Los Angeles, California, area. Honda distributor Jack McCormack discovered that the dealer was fitting trials tires on his C100s and reducing the gearing to suit offroad use. McCormack sent an example to Japan and the factory responded with the 1961 C100H "Hunter Cub" — although it was little more than a 50cc C100 Cub with the bodywork and front fender removed, and with offroad tires and a larger rear sprocket.

Honda got serious in 1964, introducing the CT200 with an 87cc overhead valve engine, 4-speed transmission, a bash plate and high-level exhaust. The rest of the bike was still definitely Cub. Removing the Cub's generous leg shield revealed the wiring harness, which the CT200 hid with a simple plastic wrap, and the air filter was still carried in the frame just below the handlebars. The CT200's main innovation, though, was the addition of a second rear sprocket, allowing for a change to the overall gearing — though the chain still had to be removed and replaced and adjusted accordingly.

The first CT90 Trail 90 "K0" of 1966 still looked like a stripped Cub, but with two important changes: the engine was now a single overhead cam design with an alloy cylinder head; and the hokey dual-sprocket arrangement was eliminated, replaced by a selectable reduction gear in the transmission, effectively giving the CT an 8-speed gearbox. Honda called this feature "Posi-Torque." Selecting the lower ratio set required simply the flip of a lever on the transmission case.



The K0 retained Honda's centrifugal-clutch and semi-automatic transmission. In the absence of a clutch, the left side handlebar lever could be used to operate the rear brake. The only difference between the CT90's setup and a fully automatic moped was the foot-operated transmission. Neutral was also impossible to miss, being at the end of the gear selection (N-1-2-3-4). That made the CT attractive to novices and non-motorcyclists — Honda's target market. All you needed was a yearning to ride in the outdoors and a tank of gas.

As with other members of the Cub family, the CT90's frame was fabricated from steel pressings welded together to form the one-piece engine cradle, rear fender and rear suspension mounts. This was connected to the steering head by a large diameter steel tube, which was gusseted to the steering head with steel plates. The rear swingarm was similarly assembled from steel pressings.

Wheels were 17-inch running on 2.75 knobby tires with 4-inch single-leading-shoe drum brakes front and rear. For 1969 the Trail 90 "K1" was tidied up, with a sturdy plastic cover now hiding the main frame tube, wiring and air filter, plus the unsuitable leading-link fork was dropped in favor of a telescopic fork.

Did the CT90 deserve the title "pack mule" given to it by Cycle News in 1973? Cycle Guide took one into the bush in 1979 and concluded that: "The 8-speed transmission gave the bike the stubborn agility of a mountain goat... in fact, I cannot think of a place it will not go." Comparing it to a horse, they said the CT90 "eats cheaper, won't throw you off on purpose, will carry more and is easier to load onto a trailer."Concluded British journalist Frank Melling, "This is not offroad riding as we currently understand the term. The CT is a truly remarkable, not to say practical, dirt bike."

The irony is that the CT90, based on a prosaic, durable and practical (but ultimately disposable) utility bike, will now command good money in the market. Especially prized are the early 1966-68 "K0" models. MC


Contenders: Offroad alternatives to Honda's CT90

1966-1967 Kawasaki J1TR/TRL 80

  • 1966-1967
  • 8hp @ 7,000rpm/56mph (est.)
  • 81.5cc rotary valve air-cooled 2-stroke single
  • 4-speed rotary shift, chain final drive
  • 168lb (dry)/188mpg (factory ad)
  • Price then/now: NA/$800-$2,000

Introduced in 1966, the J1TR used a rotary-disc-valve intake system like the Yamaha Trailmaster. This fed the 81.5cc alloy head 2-stroke single, driving an unusual 4-speed transmission, also known as a "rotary shift.&" Gear selection went N-1-2-3-4-N, continuously! It was a setup that confused many first-time Kawi pilots.

The TR was intended for on/offroad use, though unlike its Honda competition it never acquired dual-range gearing. The engine attached to a pressed-steel spine frame running on 2.5 x 17-inch wheels with a telescopic fork at the front and a spring/damper controlled swingarm at the rear. The TR featured a high-level exhaust, knobby tires, sprung front fender and engine skid plate. Available from 1967 was Kawasaki's "Superlube" automatic oiling system, adding "L" to the model designation.

As well as the TR/TRL, the J1 range included the base street model J1, the J1D with electric start, and the J1T touring. The J1s were replaced for 1969 by the 90cc G1 with slightly more power; and the 100cc D1.

1964-1969 Yamaha YG-T80 Trailmaster

  • 1964-1969
  • 6.2hp @ 10,000rpm/41mph
  • 81cc rotary valve air-cooled 2-stroke single
  • 4-speed, chain final drive
  • 140lbs (dry)/170mpg (claimed)
  • $367 (1964)/$1,000-$2,500

The YG-T was based on a "conventional" street bike, the YG-1. Its pressed-steel spine frame formed the rear fender, located the engine and rear suspension, and connected to the steering head. Bolted to the frame was a rotary-valve 2-stroke engine with 4-speed transmission and (from 1965) Yamaha's Autolube automatic oiling system. The YG-T included off-highway features like braced handlebars, a bash plate and knobby tires, but retained the street YG-1's low-level exhaust.

For 1968, the YG-5T added a high-level exhaust with heat shield, the engine bash plate was now attached to two slender front frame tubes, 17-inch wheels (up from 16), electric start, and dual rear sprockets allowing the choice of a lower ratio gear set.But the Trailmaster never got an integral dual-ratio transmission like Honda's.



At just 140 pounds dry, the Trailmaster proved more than capable on dirt trails, but struggled on the street with its short gearing. The YG-5T's dual gearing helped with this issue — if you had time to change sprockets.

Larry
1/9/2019 8:44:53 PM

As a young boy, the bike of dreams. Those knobby lugged tires, the allure of adventure in the wild, it just didn't get much better than this. While the Cub stepthru 50 may be likened to a moped with gears (heavier frame and design) the Trail 90 with the OHC motor was a sprightly running machine approaching 55 mph, maybe 60 with a tailwind! They sipped fuel achieving 75-125 mpg based on how aggressive the ride. They now represent the gold standard of small displacement bikes from the 60's and 70's. Able to be tagged, popular still with hunters, and a popular standby for motorhome campside exploration or a run to town for a quart of milk. With simple maintenance and occasional oil change, these little dynamos seem to run forever!


H Glen
11/17/2018 8:41:02 PM

Great for the trail. Dad and a hunting friend got a couple of them in 1970. Myself and a buddy demonstrated their capabilities after heavy snowfalls. Riding on the road, off road, neighborhood and high school lawns, etc.


Arif
9/27/2018 7:08:40 AM

I have 7 of these amazing bikes.











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