To maintain a balanced motorcycle with a monster-tire application, JIMS introduced its right-side-drive six-speed overdrive transmission, which eliminates the need to offset the drivetrain. The right-side-drive transmission can handle a 280/300-series tire and includes critical design improvements for improved street use and reliability.
For example, standard right-side-drive transmission designs use a longer mainshaft than stock. The longer shaft, combined with high-torque loads from big engines and fat tires, causes mainshaft flex, which can result in premature part failure. To minimize flexing of the mainshaft, which is common in high-horsepower and wide-tire applications, JIMS' right-side-drive design incorporates an outboard support bearing for mainshaft integrity. A built-in pump pressure-feeds lubrication to the support bearing through an oil galley in the trap door and pulley cover.
The right-side-drive gearbox includes six speeds, with top gear being an overdrive. The internal gear ratios are as follows: close-ratio 2.91 First, 2.19 Second, 1.59 Third, 1.22 Fourth, 1.10 Fifth, and 0.87 Sixth. Gear ratios from First through Fifth are spaced slightly closer together than the Fat 5's intermediate ratios.
JIMS' right-side-drive transmissions are available for Evo- and Twin Cam-style transmission mounts and will bolt into most RSD-specific frames with no frame modifications. All case covers are CNC-machined from billet aluminum, then polished and chrome-plated. Black, silver, and polished cases are available. Additionally, the gearbox can be ordered with either hydraulic or cable clutch actuation.
If you're building a high-torque engine or wide-tire bike, JIMS' Fat 5 overdrive and right-side-drive six-speed transmissions may just be your ticket to hooking up ground-stumping power and a smooth, balanced ride.
We wanted to see for ourselves what the JIMS Fat 5 overdrive and right-side-drive six-speed transmissions look like, so we decided to disassemble each one. Follow along and see for yourself. We'll start with the Fat 5.
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JIMS took advantage of its compact shifter design and redesigned every Fat 5 gear to incre
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Here's the fully assembled JIMS Fat 5 overdrive transmission with Evo mounts and black Sof
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Disassembly starts by removing the top cover's four Allen-head cap screws and the cover, e
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After unbolting four cap screws, the pillow blocks and shift drum were removed as a unit,
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The next step was to remove the chrome side cover, which is attached to the trap door with
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After removing the socket set screw near the top of the trap door, the shift forks and shi