Understanding Suzuki’s EFI Mapping Coupler System

Story by Jeff Belknap

The 2023 Suzuki RM-Z250 (and RM-Z450) comes with three easy to use, plug in couplers that change the EFI tuning – a system similar to what Kawasaki uses.  The stock coupler is White/Black tape, the Grey coupler is +4% Richer, and the White coupler is -4% leaner.

With the richer Grey coupler, we felt a bit more overrev; however, it flattened out the powerband down low. If you’re an aggressive rider who likes to stay up in the revs, this is the coupler for you as it transfers more of its power into the top end. The White coupler is -4% leaner, which is the one our vet riders preferred. It gave the bike a more responsive powerband, especially off the bottom, and revved a little quicker than stock, getting into the meat of the power sooner.

How do I change this coupler? The coupler is located behind the radiator shroud on the throttle side of the bike. There is a rubber grommet that is attached to a bracket on the frame. Simply pull it down, that will allow access to the wire loom. There is enough slack in the wire loom to pull out past the shroud, this will allow you to make your change and re-install.

With how easy Suzuki made changing these out, we highly recommend trying all of them before going out and buying an expensive aftermarket ECU. It’s not to say that an aftermarket part won’t make a difference, but this could be all you need and it comes with the bike so why not try them all? There is a noticeable difference to suit your riding level and terrain and we do advise trying them all on the same day and conditions to really notice the difference.

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