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Honda's idle drop procedure |
As a career powersports tech and votech educator, I find it humorous that user forums propagate a technique that has so little to do with proper tuning. Just one more instance of the powersports media, and in this case, user forums, latching onto the trivial at the cost of the vital. Not to mention taking something completely out of context.
Honda published in later carbureted model service manuals a technique they called the idle drop procedure. It's goal was to adjust the idle slightly lean. For emissions purposes. And it was a reinterpretation, if you will, of a procedure practiced in the car world, including in Honda car dealerships as well as in domestic car shops. The car mechanic adjusted the car's idle mixture while a propane bottle was screwed onto the carburetor through a special adapter. He adjusted the pilot screw until he got the best, highest idle, then he removed the propane before giving the dar back to the customer.
The result of course was a carburetor whose idle circuit was a calculated amount out of adjustment. Too lean. It sounds funky today, doesn't it? But this is exactly the same scenario as Honda's powersports targeted idle drop procedure. That is, the same goal, and the same path to that goal. That is, a purposely mucked up idle mixture setting. In the motorcycle version (probably developed with a consideration for the motorcycle shop's fewer financial resources), instead of the propane bottle, the mechanic uses an electronic tachometer (this became a required tool at the outset of the emissiins era in 1978). He got the perfect idle mixture just like the car mechanic did, then using the tach, he screwed it up, ruined it, by turning the screw inward enough to display a 50 rpm or 100 rpm drop, approximating thereby a calculated leaning of the carburetor. And he left it like that. As in the car example, the customer got his bike back with an improperly adjusted pilot screw.
It's ironic, this advocating of an emissions specification as a tuning adjustment. Honda's idle drop procedure is not part of correct idle mixture screw adjustment. Call it whatever you like, it is not tuning.
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Last updated January 2025 Email me © 1996-2025 Mike Nixon |