Said to be the smallest production twin-cylinder motorcycle at the time, Yamaha’s HS1 wasn’t a powerhouse, but even at 89-cc, this was a fun bike to ride if you didn’t expect it to be a stoplight beast. This 1970 Yamaha HS1 90 Twin can be found here on Facebook Marketplace in Louisville, Kentucky, and they’re asking $2,500 or best offer. Here is the original listing, and thanks to Pnuts for the tip!
Yamaha made a somewhat similar HT1 90, which was an on/off-road bike with an upswept pipe, but it was a single-cylinder. The HS1 is a twin-cylinder street bike, and they’re small but are fun for neighborhood jaunts. Our first motorcycle as kids was a late-60s Yamaha YL-1 Twinjet 100 street bike. It had a pressed-steel frame and was a good little street bike, but visually, the newer HT1 looked more modern, like Yamaha’s bigger bikes.
We rode that little Yamaha Twinjet up and down our gravel road endlessly, back in the glory years when a person could do such a thing as barely a two-digit kid (10-12 years old). Then we put a knobby tire on the back wheel and a bigger rear sprocket, and we used it as a makeshift trail bike. It was good enough, back when good enough was actually good enough for most people. I’d source some period-correct turn signals and use this HS1 90 for errands around the neighborhood.
This example has only traveled 1,452 miles over the last 56 years, hardly adding any two-stroke smoke to the neighborhood. A few years later, once we were of driver’s license age, we had a somewhat similar-looking 1970 Yamaha 250 DS6-B, and I’ve been looking for another one over the last four decades with no luck. I know they’re out there. This 198-pound Yamaha 90 twin looks great in the photos, although the gas tank has been through a few teenage riders, it looks like. Or something has happened to it over the decades.
The little jewel-like engine is Yamaha’s 89-cc two-stroke oil-injected twin-cylinder with around 5 horsepower. The engine sends power through a 5-speed transmission to the rear via a chain and sprockets, as you’d expect. Yamaha’s famous Autolube oil-injection system keeps things slippery for those tiny pistons, about the size of the dial on a watch, and the tiny carburetors are very cool. The seller says this bike runs and rides great and has a clean title. This whole engine would look great on your bookshelf, but I’d rather have it in this motorcycle. Have any of you owned a small twin-cylinder motorcycle like this Yamaha 90?
Well shiver me timbers, if it says Scotty G, were going to learn something. Never knew there was such a thing, the “Twin-Jet 100” got all the thunder, not that us macho men AND WOMEN cared about such things in Beer City. Oh sure, every once in a while, one of these annoying things would leave a smoke screen as they zinged past, some college student hanging on for dear life, of no concern. You could say Wisconsin was the most in denial of all the states. Nothing could possibly replace our Harley/AMC/Briggs and Stratton business,,,
While Honda shocked the world in 1969, the “others” were slow to catch on, and there was still a market for these, just not for long. Like I said on the Kawasaki post, I bet more people did exactly what Scotty did, and these made really dependable dirt bikes, in that, not much could kill them. Obviously, this particular bike saw none of that, and sadly, I see little, if any interest today.
And the same trick worked when trading a clean Hodaka Ace 100 straight across for a Bultaco 250 Pursang-a Hodaka headlight and Yamaha taillight on it, licensed it and rode it to school, never mind that neither light was worked.
Simpler times.
Very clean old Yamahammer, Scotty, and like you said Howard-learned something new again today!
Well, you always learn something new, no matter how old you are. A Twin-Jet 90? Obviously they made it and sold it. I do have to admit that I’m a little curious how that would be to ride it. I can just imagine, 220 lbs. on that. Well, a few years ago there was 220 lbs. worth of rider torturing the back of a Honda Spree. And it hasn’t been that long ago I rode a Twin-Jet 100.
I’ll bet my two grandsons would enjoy something like this…
Would a one cylinder of the same displacement make more power ?
Scotty, I got to say you learned me something today. From the age of 8 to 15, I had my face in Boy’s Life and motorcycle magazines the want ads too. All while dreaming about mini bikes and trail bikes. I did not know these existed, the cylinders must have been about the size of a roll of quarters.
My dad always gave me the opportunity to work earning money cleaning up after construction, packing lumber, etc. After destroying a Bonanza mini bike, I was ready for a trail bike. We went to a dealer one Saturday and there it was, a barely used orange Suzuki 1971 TS 125 Duster. Dad helped me pay for it after we made a deal on how many hours labor I owed to pay him off.
I still get a little excited when I see on on the interweb.
Back in the day a kid had a Twin Jet 100. Not having the $1.25 to replace the NGK spark-plug he rode it on the one cylinder for near a month. My buddy and I were there at the Yamaha shop on Gandy Blvd. in St. Petersburg, Fl. when he put the new plug in and kick started it. KA-BLAM! It backfired, caught the gas and oils in the r/h cylinder on fire. There was not one fire extinguisher in the cycle shop. He cried watching his beautiful bike burn to the ground.
Quite the gem. This would make great garage art, but I would be tempted to ride it every weekend.
Had this exact same HS-1 in 1970, was a great fun bike to ride. not a powerhouse on the road as I lived 6 miles from town where I worked.
it was great to zip around town. I worked at the local Yamaha shop and a customer fell in love with my bike and we traded even up for a 1962 Triumph Hearld. which was a great deal but I did miss that neat little bike.