Honda GP bikes of the '60s - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 7 (permalink) Old 02-09-2016, 11:19 PM Thread Starter
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Honda GP bikes of the '60s

Honda RC142 (1959) - 2-Cylinder 125cc GP Racer

18.5 bhp at 13000 RPM, max revs 14000 RPM
Flat-side Keihin carbs with remote float chambers
6-speed gearbox

https://youtu.be/8unha2DhCFE

Honda RC143 - 2-Cylinder 125cc GP Racer

23 bhp at 14000 RPM
Flat-side carbs with remote float chambers
Uses bevel gear drive to camshafts
Max speed over 180 Kph (112 MPH)

RC143 engine rebuild: https://youtu.be/V2wnOOLDpEs

Honda 4RC146 (1965) - 4-Cylinder 125cc GP Racer

Modified 2RC146
30 bhp at 17,000 rpm
7-speed gearbox
Max speed over 180 Kph (112 MPH)

Part 1: https://youtu.be/WjJl_RvRhxI
Part 2: https://youtu.be/-tB1v1AIGaw

Honda RC116 (1966) - 2-Cylinder 50cc GP Racer

Air cool 50cc 2-cylinder
Flat-slide carbs
twin max power: 16hp @ 21500 RPM
max revs: 22500
9-speed gearbox
max speed over 175 Kph (109 MPH)

https://youtu.be/vDd0kVnnqfg


Honda RC149 (1966) - 5-Cylinder 125cc GP Racer

Air-Cooled 4-stroke Inline-5 DOHC 4-Valve Gear Train
Two-piece crankshaft with 3 cylinders at 120 deg, and 2 cylinders at 180 deg.
Over 38 BHP @ 20,500rpm (the 2-piece crankshaft reduced max revs from 21,500)
8-Speed Transmission
Max speed over 210 Kph (131 MPH)

https://youtu.be/qLYo8io6fBA


Honda RC166 (1966) - 6-Cylinder 250cc GP Racer
Over 60PS at 18000 RPM
7-speed gearbox
Max speed over 240 Kph (150 MPH)

https://youtu.be/o57JwibqCb8


Honda RC174 (1967) - 6-Cylinder 350cc GP Racer
Over 65Ps at 17000 RPM
7-speed gearbox
Max speed over 250 Kph (156 MPH)

https://youtu.be/KoSU7aRBRgg


Honda RC181 (1967) - 4-cylinder 500cc GP Racer
85PS at 12000 RPM
6-speed gearbox
Max speed 260 Kph (162 MPH)

https://youtu.be/R8Wq4Mn-9NA
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Last edited by SubSailor; 02-15-2016 at 10:44 AM.
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post #2 of 7 (permalink) Old 02-11-2016, 09:11 PM
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What a treat...A lovely collection of great sounding GP Hona bikes. Thanks as always for sharing Sub!

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post #3 of 7 (permalink) Old 02-12-2016, 10:12 AM
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Very cool stuff SubSailor.
The way they snap the throttle after starting the bike: is that a two-stroke thing?

John, 2000 RC51 #000100

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post #4 of 7 (permalink) Old 02-12-2016, 12:09 PM
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JonDog9;

Caveat, I'm no Kevin Cameron with an encyclopedic knowledge of all things two stroke...

The carb on the RC116 likely does not have the complexity of a modern carb, which have pilot jets, main jets, metering circuits, etc. (and it's probably not a multi-tapered needle either). As a result, the bike is jetted to run at the rpm's where the main jet has the most influence (1/2 to full throttle).

At low revs the motor is going to want to load up and foul the plugs. Revving as in the video will limit that likelihood to a degree.

On a largely unrelated note; is there no front brake on that RC116? The front hub is awfully small...

r/
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post #5 of 7 (permalink) Old 02-12-2016, 08:25 PM Thread Starter
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The main reason they constantly blip the throttle is because the carbs have no idle circuit.
You'll notice they simply let the throttle close to kill the engine.
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post #6 of 7 (permalink) Old 02-12-2016, 08:28 PM Thread Starter
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Quote:
Originally Posted by David_Stack View Post
JonDog9;

Caveat, I'm no Kevin Cameron with an encyclopedic knowledge of all things two stroke...

The carb on the RC116 likely does not have the complexity of a modern carb, which have pilot jets, main jets, metering circuits, etc. (and it's probably not a multi-tapered needle either). As a result, the bike is jetted to run at the rpm's where the main jet has the most influence (1/2 to full throttle).

At low revs the motor is going to want to load up and foul the plugs. Revving as in the video will limit that likelihood to a degree.

On a largely unrelated note; is there no front brake on that RC116? The front hub is awfully small...

r/
Dave
The RC116 uses a bicycle type caliper brake that presses the brake pads against the rim.
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post #7 of 7 (permalink) Old 02-12-2016, 08:32 PM Thread Starter
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Quote:
Originally Posted by jondog9 View Post
Very cool stuff SubSailor.
The way they snap the throttle after starting the bike: is that a two-stroke thing?
These are all twin-cam 4-valve 4-stroke bikes.
To reduce friction, they only use 2 piston rings, a top compression and bottom oil ring.
No oil scraper ring is used, so you get more oil leak-by.
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