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Discussion Starter · #1 ·

**Please note: If you use a much higher octane ratio than recommended your engine

may not perform optimally. This is due to slower flame propagation. Ensure you are

using 87 octane in the US/Canada, or 91 octane in other countries and that it is a

good quality fuel. If your hear a knocking noise coming from the engine try a fuel with
a slightly higher octane rating!..

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8,369 Posts
Discussion Starter · #3 · (Edited)
Other interesting find can be found reading their manual.

another interesting read
Ensure when you install your new Yuminashi 160 Ultimate Kit, the
outside diameter of your header isn't larger than 1 inch (25.4mm).
Optimal inside diameter is between 21.5-21.8mm (0846–0.858

another interesting read about the stock Grom heads with their FI unit
6.Our stand-alone ECU is a dual-mode system which gives the rider the ability to choose between two different modes/maps.
Mode #1: Touring mode
This mode is the most economical mode and may be used for “daily driving”. In this mode engine RPM is limited to 10,500 RPM. This is the default mode which the unit will be in from the factory.
Mode #2: Racing mode

Racing mode increases the engine RPM limiter to 12,000RPM. In order to switch to Racing mode the included jumper plug needs to be installed.
**Both modes can be separately adjusted or programmed by your official Yuminashi dealer.

The 8-Hole Big Bore injector included in the kit has been matched to provide the optimal flow rate for use with the 160cc cylinder kit
and has proven to be the perfect match in conjunction with the stock Honda Grom/MSX125 throttle body.
The benefit of this larger flow injector is it allows us to maintain a duty cycle that does not push the limits of the stock 125cc injector. This ensures that throughout the RPM range the AF ratio never leans out and causes engine damage. It promotes better fuel atomization, results in smoother throttle response and better overall performance.
Because everything has been optimized for the stock head it is not necessary to modify the port diameter on the intake runner or exhaust manifold side. If they are modified reduced performance will result due to decreased gas velocities.
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