Cold and Hot Idle Set Procedure on M-M EFI

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By Patrick Zambori,

This describes a method to set cold and hot idle speed on Magneti-Morelli EFI systems.

First, when it comes to setting cold idle, the service manual leads you down a path of frustration. I have a very simple and effective way of adjusting it. If you start the engine stone cold and it idles below 1200 rpm (after it stabilizes) then turn the cold idle screw (in linkage, on the side that rotates with the throttle plates) in.  If it's over 1300 rpm, then turn the screw out (therefore, set cold idle speed at 1200 rpm for TC-88's). It's that easy .  Also, to guarantee that the idle will be recognized by the ECM, I run the bike until it's fully warmed up, turn the hot idle (in the throttle body, forward of the front intake, near the bottom) up to 1200 rpm, shut off the ignition and pull the 5 amp fuse (in the fuse holder on the ECM brackett), run a lead from the cold (relay) side of the 5 amp socket to ground. Let it sit for 15 minutes or longer if practical, then put the fuse back in and warm it back up, turn it back down to 1000. Works like a charm.


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