More, but smaller

by "Cé hé sin" (michael-m-mouse)
Published 02/28/2017 at 19:15

Tags: Honda ; RC 148 ; RC 149
STARS: 5

More than fifty years ago Honda had a predicament. They were racing four stroke motorcycles and being beaten (edit: concerned about being beaten) by the two strokes of the other Japanese makers. What do do? Well, two strokes produce power each time as piston moves downward while a four stroke does so only every other time. They needed to get their pistons to move a bit faster then and this was easier to arrange if they had more but smaller ones. Enter a 50cc twin. This was good, but no need to stop there. Honda wanted to do well in the nest class up, 125cc and what better to use but two and a half of the 50cc twin. Enter the 125 five cylinder RC 148 of 1965 and its successor, the RC 149 of the following year. The 149 won the world championship of that year following which the rules were changed to outlaw multi cylinder engines and as far as Honda was concerned that was that.

Meet an RC149.

Yes, it had drum brakes in spite of going 130 mph. Different times.

Meet its engine (actually an RC 148 but never mind). Count the five little carbs.

You want to hear one starting up, don’t you? Of course you do. No, the chugging noise at the start isn’t it. Turn up the volume and wait.

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It produced about 35 bhp at 20,500 rpm and had a red line of 21,500 rpm. Then again, it wouldn’t run at less than about 17,000 rpm and had an effective power band of about 1,000 rpm. You’ll see why it had eight or nine speed gearboxes then. Twenty-one thousand revs was an awful lot fifty years ago for an engine designed with pencil, paper and slide rule.

You want to see it running too don’t you? Of course you do.

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Just about everything about the engine was exotic. Each of the conrods was subtly different. Almost every part including many fastenings was specially made. Some of the oil passages were 0.5mm wide. The crankshaft was built up from about a dozen tiny pieces and was so light you could deform it by hand. Oh, and it wasn’t a conventional inline five. Oh no. One side was designed as a twin and the other as a triple so one side of the crank had 180 deg spacing and the other 120 deg.

So there you have it. What Honda could do before they went all boring.

Oh, and they did a 250 cc six at the same time. That won championships too.

Replies (6)

"Bman76 (hates WS6 hoods, is on his phone and has 4 burners now)" (bman76-4)
02/28/2017 at 19:22, STARS: 1

The 250 sounds so much angrier too.

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"DipodomysDeserti" (dipodomysdeserti)
02/28/2017 at 21:12, STARS: 2

Honda wasn’t being beaten by other Japanese makers when they started racing. The world was dominated by Euro bikes at the time, and Honda cleaned the floor with them.

Honda was the first Japanese manufacturer to enter a World Moto GP event, placing three bikes in the top ten at the ‘59 Isle of Man 125cc class. They became the first Japanese manufacturer to win a World Moto GP title three years after they started racing. They became double world champions in 1962. They won the Isle of Man In the 125 and 250cc only three years after they started competing. They placed 1-5th in both the 125 and 250cc classes that year as well. Other Japanese manufacturers didn’t even compete on the global scale until Honda whooped all the Euros.

They had already dominated everyone in the 125cc and 250cc classes and moved on to the 500cc bikes by the time the RC149 came out. In 1966 (the year the RC149 debuted) they won the World Moto GP championships in the 50, 125, 250, 350, and 500cc classes. I’m very proud to own some cutting edge tech from Honda’s glory days.

I’ll be dropping a write up on the 450 tomorrow. The RC149 is my favorite motorcycle of all time. I have heard that it was extremely hard to machine the valves because theu were so small. It had four valbes per cylinder...on a 125cc five cylinder engine. Insanity.

"Cé hé sin" (michael-m-mouse)
03/01/2017 at 04:46, STARS: 2

Also, you could put two of the pistons on a credit card with room to spare. You had to very careful if lapping the valves because they would twist.

Have a crankshaft .

"pip bip - choose Corrour" (hhgttg69)
03/01/2017 at 05:30, STARS: 0

awesome!

"aqualungdarmah" (aqualungdarmah)
03/01/2017 at 12:07, STARS: 1

Honda did not win the 500cc riders championship until 1983 with Freddie Spencer

"DipodomysDeserti" (dipodomysdeserti)
03/01/2017 at 12:30, STARS: 0

Correct, my bad. They won the 125, 250 and 350cc that year.