Name: 4-SPEED CLOSE MISSION ASSY. (12V GB2 / GB4 / GB5 / GB6 ENGINES)
Brand: YUMINASHI
SKU: 23511-12V-4SP
Price: 101.53 EUR
Availability: InStock

Description

● YUMINASHI 4-SPEED CLOSE MISSION ASSY. (12V GB2 / GB4 / GB5 / GB6 ENGINES) (23511-12V-4SP)

● The 4-Speed close mission kit has been developed to change the stock 3-speed transmission or your stock 4-speed transmission into a sports 4-speed close mission transmission and this for the 12V 50cc, 70cc, 90cc, 100cc and 110cc engines with the kickstart sprocket included in the set.

● A 4-speed gearbox on a Honda motorcycle offers better fuel efficiency and a wider range of speeds, allowing for more both relaxed cruising and better acceleration, compared to a 3-speed gearbox, and the 4th 22/22T sports gear makes it much easier to gain top speed compared to an overdrive.

● Here's a more detailed breakdown of the benefits:

Fuel Efficiency:
The extra gear in a 4-speed gearbox allows the engine to operate at a more optimal RPM (revolutions per minute) range, leading to better fuel economy, especially at higher speeds.
Wider Range of Speeds:
A 4-speed gearbox provides a greater range of gear ratios, enabling smoother acceleration and a more relaxed cruising experience.
Improved Acceleration:
The 4th gear can be designed to have a lower numerical ratio, which allows for quicker acceleration without the engine over-revving.
Reduced Engine Noise and Wear:
By keeping the engine RPM within a more efficient range, a 4-speed gearbox can reduce engine noise and wear, especially during long highway rides.
Better for highway:
A 4 speed will have taller gears that require less shifting around town. While they do almost always have a lower top speed, they're often quicker than their 5 speed counterparts

● GEAR COMBINATION:

G1: 14-31
G2: 18-27
G3: 20-25
G4: 22-22

● DESIGN/GEARBOX NATURE:

● We recommend a safe maximum of 12 to 15 horsepower for this specific gearbox design.

● To give you a baseline for comparison, a stock Honda engine using the GB5 or GB6 crankcase (like the 97cc engines found in the factory Honda EX5, Super Cub 100, or Astrea) produces roughly 7 to 8 horsepower directly from the factory.
This means your new close-ratio assembly is built to safely handle nearly double the original stock power of those engines...

● There is a physical limit to how much power these older 12V (GB2/GB4/GB5/GB6) engine architectures can take.
These specific engine cases are quite narrow, meaning the transmission gears themselves have to be manufactured quite thin to fit inside the crankcase.
When pushed beyond 15 HP, the high torque can easily cause the thin gear teeth (particularly in 3rd and 4th gear) to shear or break under heavy load.

● For comparison, when builders are doing high-performance builds (20+ HP), we usually recommend switching to the newer Honda Wave 125 engine architecture.
The Wave 125 was designed with a much wider crankcase, which accommodates significantly thicker, heavy-duty gears that can easily handle high horsepower and aggressive riding without breaking.

● As long as your current build is producing under 15 HP, this 4-speed gearbox will perform beautifully and give you excellent, snappy acceleration.
To get the maximum life out of it, we just recommend smooth shifting and avoiding aggressive "clutch dumps" from a standstill.

※ This 4-Speed Close Mission Assy. can be installed in combination with the semi-automatic clutch, and the manual clutch.

※ Not every engine is using that gearbox lock plate at the end of the counter shaft and can be removed.

SMART SHOPPER TIP:
※ BUYING MORE THAN 1 PIECE CUT THE TRANSPORT PRICE, AND YOU RECEIVE A 10% DISCOUNT ON TOP OF IT!

※ B2B:

Purchases between 2 & 4 pieces of this product will receive a 10% DISCOUNT
Purchases between 5 & 9 pieces of this product will receive a 15% DISCOUNT
Purchases between 10 & 19 pieces of this product will receive a 20% DISCOUNT
Purchases between 20 & more pieces of this product will receive a 25% DISCOUNT
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