Name: 4-SPEED CLOSE MISSION ASSY. (FOR 12V WIDE-CASE 90CC/100CC/110CC ENGINES)
Brand: YUMINASHI
SKU: 23511-GN5-4SP / 23511-12V-4SP
Price: 1153.98 SEK
Availability: InStock

Description

● YUMINASHI 4-SPEED CLOSE MISSION ASSY. (12V WIDE-CASE CLOSE-RATIO GEARBOX SET) (23511-GN5-4SP)

● A close mission 4-speed gearbox on a Honda motorcycle allowing more relaxed cruising and better acceleration, 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 shorter gear in the close mission 4-speed gearbox allows the engine to operate at a more optimal RPM (revolutions per minute) range, leading to better fuel economy.
Wider Range of Speeds:
A close mission 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 & HORSEPOWER LIMITS:

● For standard narrow-case architectures (C70, Dax, CRF50), we recommend a safe maximum of 12 to 15 horsepower for this specific gearbox.

● To give you a baseline for comparison, a stock Honda engine using these crankcases produces roughly 5 to 7 horsepower. This means your new 4-speed conversion assembly is built to safely handle double the original stock power.

● The Hidden Cause of Gear Failure: Many builders assume transmission gears break simply because the steel is too weak. In reality, there is a physical limit to how much torque standard factory aluminum crankcases can take. When pushed beyond 15 HP, thin OEM crankcases flex and distort under load. This flex pushes the transmission mainshaft and countershaft out of alignment. The gear teeth lose their perfect, deep mesh and ride up onto the fragile tips, causing the teeth to shear off instantly.

● The High-Horsepower Solution (25+ HP): If your build targets 20 to 30+ horsepower, you must eliminate crankcase flex. For these extreme builds, we engineered the #11150-KFL-690 Yuminashi Heavy-Duty Wide-Case (Nice110 Platform). Cast with almost double the aluminum wall thickness of a stock engine, these reinforced cases physically prevent the shafts from pushing apart.

● When you combine a Wide-Case 4-Speed Gearbox with our Heavy-Duty Crankcase, the perfect shaft alignment unlocks the true strength of the gears, safely handling 25 to 30+ HP. Furthermore, this Heavy-Duty case utilizes a crankshaft-driven Nice110 oil pump and is designed to accept modern, large-displacement Wave125i and GROM125 crankshafts, cylinders, and cylinder heads for ultimate power generation.

● Conclusion: As long as your current narrow-case build is producing under 15 HP, this 4-speed gearbox will perform beautifully and give you snappy, reliable acceleration. To get the maximum life out of it, we recommend smooth shifting and avoiding aggressive "clutch dumps" from a standstill. ※ This 4-Speed Conversion Assy. can be installed in combination with both the factory semi-automatic centrifugal clutch and aftermarket crankshaft-mounted manual clutches.

● Complete Application List for 23511-GN5-4SP (Wide-Case Close-Ratio Set)

Honda C100 / EX5 / Dream 100 / Astrea Grand / Supra 100 (GN5)
Honda Wave 100 (Early KFL) & Wave 100S / Wave 100Z U-Box (KFM)
Honda Wave 110 / Wave 110S (Carbureted KEV / KFL — 1999–2008)
Honda Nice 110 / Nice 110S (KEV / ZN110 — both Semi-Automatic and Manual Clutch models)
Honda XRM 110 (Philippines KEV)
Honda TRX90 (1993–2005 HF7), TRX90EX (2006–2008 HP2), & TRX90X (2009+ HP2)

※ Can be installed on the Carbureted Wave 110 (KEV) & Nice 110 — Does NOT fit 2009+ Wave 110i PGM-FI (KWB/KWW) or Nice 125 (KPH)", since the 110i and 125 switched to a completely different transmission platform.

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Purchases between 2 & 4 pieces of this product will receive a 10% DISCOUNT
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