Stop cussing that early EFI system, just replace it!


Zipper’s has taken the popular ThunderMax® EFI electronics and merged it with a single-throat Delphi®-style throttle body (with the help of some specially made parts) and developed this full conversion kit for bikes with H-D’s earliest Magnetti-Marelli EFI systems. This kit allows you to retain the original wiring harness and gas tank, while upgrading to similar components used in the highly durable and reliable Deplhi®-based bikes of 2002-2005.


Gone is the idle stepper-motor and its funky linkages that caused wandering idle and hard starting! Gone are the limitations of the stock throttle body air flow and hard-to-find injectors! In its place are modern throttle body configurations available in multiple bore diameters allowing easy selection of performance injector sizes! This is THE KIT to use, especially for engines with performance modifications as our vast selection of ThunderMax base maps allows fast set-up and tune-in.


Instant starting! Consistent idle! Superb performance! It’s all here in this kit. The ThunderMax with its integrated AutoTune transforms this system to full closed-loop automatic air/fuel ratio correction, maintaining your custom tune no matter what the ambient conditions or elevation you choose to ride in! Includes detailed installation instructions and TMax Tuner software. Requires exhaust system equipped 18mm oxygen sensor bungs or modification to accept 18mm oxygen sensors.


You’ll fall in love with your bike all over again!


These kits are built to order with special parts for each application, Please contact a sales representative for lead time.


Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.

Weight 1 lbs

Emissions Compliant

Engine Type

Fuel / Air

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13 reviews for Zipper’s® Marelli Conversion Kit with ThunderMax® for 1999-2001 Twin Cams®

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