Two Speed Clutch

The original Honda Express, NC50, was a single speed, oil bath centrifugal clutch, transmission. In 1981, they changed to a better centrifugal clutch, a bit larger, but much lower weight shoes. In 1982 they introduced a two speed transmission. The way they did this was replace the clutch with a planetary transmissions with two clutches in the same package as the 1981 clutch.

It is a very cool little package. I hope some engineer got an award for this clutch and transmission. So much of the NC50 is really simplistic, it is surprising to see something this elegant in the engine. It reminds me of the inside of a mechanical watch.

Here's a comparison of the three different clutches, I have. The 1977 through 1980, the 1981 single speed and finally the two speed clutch from a 1982 engine:

All three of them have a 14 tooth primary sprocket. This means that the final gear ratio is the same as the single speed clutches, it just introduces a lower "first gear".

Does the two speed transmission help? Not really. I have a stock 1982 Honda Express NC50 with the two speed transmission. The first gear helps it get off the line a little quicker, but then the shift to high gear takes a second or two, introducing a lag. Then it doesn't go any faster since the final drive ratio is the same.

The next motor I am building, is the 1982 NC50 that has this clutch. I haven't decided whether I will keep the two speed clutch or switch back to the 1981 single speed clutch. I am concerned that 10+ horsepower could shred some of small parts in the planetary transmission.

Here are some more pictures of the 1982 clutch: