The Honda CT 90 was a small motorcycle manufactured from 1966 to 1979. It was essentially the CT 200, produced from 1964 to 1966, except for an important change: two rear sprockets were replaced with a second gearbox and convenient “high–low” lever switch. This second gearbox also goes by the nickname subtranny. Its transmission is a four-speed with automatic clutch. In 1969, Honda improved the CT 90’s front suspension system. In 1980, Honda replaced the CT 90 with the CT 110.
My particular bike is a 1968 Honda CT 90, serial number 177,904. It’s powered by the original one-cylinder, four-stroke, air-cooled engine with a displacement of 89 cc. It has the subtranny. It has the primitive front suspension that was discontinued in 1969 in favor of modern telescopic forks with greatly increased travel. It happens to have a nice chromed-steel accessory rear luggage rack.
I got my 90 from one of my brothers-in-law in 1999. He left it in my driveway with a smile on his face, and I accepted it gratefully, even though it was filthy and nonfunctional. For one thing, the engine was seized. It sat for several months while I mulled what to do with it.
Engine. I removed the engine head. The piston was indeed seized. I pounded on it with a hammer and soaked it with WD40. Finally, multiple cycles of soaking and pounding over several days resulted in a moving piston. I further disassembled the engine (easy), and replaced the piston, rings, and gaskets with new parts. I gave the inside of the cylinder a little honing with fine sandpaper.
Carburetor. I completely disassembled the carburetor, cleaned out various gum and other (aluminum oxide?) deposits, and reassembled.
Transmission. The transmission housing had a chunk torn out of it. It leaked oil miserably. I found the torn pieces inside the transmission, epoxied them back into the housing, and reassembled.
Electrical system. The 90 got a fresh battery. I received the bike hot wired. Thus, I had a locksmith make a set of keys for the ignition. After these major (functional) restoration steps, I got the motorcycle running on a cold winter night in early 2000.
Miscellaneous. Lots of other items needed work to restore the machine to more-or-less original condition. I replaced the seat pan, added some foam to spots where the seat foam had degraded, and gave the seat a new reproduction vinyl seat cover complete with painted Honda insignia. I repainted the gas tank and cleaned out junk from the inside. I applied new matching paint to the right side of the engine. The exhaust pipe had rotted through near the back: I patched the bad spot with sheet steel and repainted the entire system. A number of parts were broken or missing, and the bike got a new red taillamp lens, one new side cover, a brake lever, and passenger footpegs. I probably replaced a light bulb or two and a tire or two. If I recall, I may have cleaned out the brake drums and cleaned and lubricated the chain. Naturally, various parts of the bike received derusting, degreasing, lubrication, and general cleaning treatments. From Ebay came an original 1967 owner's manual.
Upgrade. Over time, I came to visualize the value of the Honda 90 for climbing dirt roads and trails and thus getting me closer to trout-fishing destinations in the Sierra Nevada. Its low range is indeed satisfyingly low.
It also occurred to me to add a larger rear sprocket for enhanced hill climbing. This I did by obtaining a 60-tooth rear sprocket (brand name Webco) on Ebay. Apparently, this was an obscure, rare accessory one could obtain to alter one’s bike way back in the day. Unfortunately, for some reason, I needed to deepen all of its internal grooves to accept the 45 teeth on the existing sprocket. Naturally, the chain received additional links to accommodate the 60-tooth rear sprocket.
Notice that this sprocket goes over, around—not next to or in place of, but around—the existing rear sprocket. How cool is that? Four bolts (and nuts) hold the two sprockets together. The subtranny is the small bulge extending from the transmission in the upper left corner of the photo. The bike may not drive city streets as fast as it once could, not that I've tried. But its hill-climbing abilities are now superb.
I’ve driven the Honda 90 some. Current odometer reading is 4,649. I’m guessing that the reading when I received it was about 4,400.
Its longest trip was a joyride around 2002 on California State Route 130 from Mt. Hamilton Springs to The Junction, which at that time was a rustic burger joint frequented by street bikers. Naturally, we got teased as we parked our little Honda CT trail bikes among the big Harleys.
Besides joy rides, I’ve depended heavily on the 90 to ferry me and companions—my dad, my son, and his various cousins—and our gear up to hot fly-fishing spots in the high Sierra Nevada.
Left. Dusy-Ershim Route is perhaps the most difficult OHV trail in Sierra National Forest, if not California. The only vehicles I've seen on it are highly jacked-up jeeps, quads, two-stroke dirt bikes and, of course, my particular Honda 90. I've driven the 90 the 7 miles from Voyager Rock Campground to a mile short of Thompson Lake. There, it balked at doing so-called Thompson Hill.
Below. This obscure former logging/mining road ascends 1,000 ft in 3 miles to the edge of a wilderness. It's gated off, but there's a gap that the 90 can squirm through. The Feds refuse to show the road on their published maps; they even—liars—at one time, posted a sign at the gate, Road Closed, Wilderness Area, although the road isn't in a wilderness area: only Congress can designate land a wilderness area. The 90 has hauled and trailered passengers and backpacks up and down this route many times in the 2000s.
Farther down. Kaiser Pass Road provides access from Huntington Lake to Lake Edison and Florence Lake. The 90 has done duty on the paved but bumpy one-lane stretch between Kaiser Pass and Mono Hot Springs. It's also served well on Route 7S32, which gives access to White Bark Vista Point.
Above. My son and two of his cousins at the edge of the wilderness at the start of one of our cross-country trout-fishing excursions. The 90 saved us a great deal of hiking with packs.