Mikee Minute #10 - The Idle Drop Scam

[mikenixon]

I recently got a call from a Wing rider who asked about Honda's idle drop procedure found in their service manuals. I added an article a couple years ago to my website on this, so I recommend reading that.

http://www.motorcycleproject.com/motorc ... _paper.swf

In short though, Honda's idle drop procedure is an emissions adjustment, and a very unfortunate one, inasmuch as the carburetors it applies to badly need correct idle mixture adjustment to run properly, particularly 80 and later models. The procedure has you find the best idle while turning the four screws, then deliberately muck it up, making the engine not as responsive to throttle, for emissions purposes. It is not in any sense recommended.

[Whiskerfish]

Interesting read!! I have generally been pleased using the idle drop plus 1.5 turns out. On most of these bikes that seems to result in a fairly good mix at idle.

To me the idle drop is a good second check that the idle circuits are working as advertised. So many folks have issue with the idle circuits and this check provides confidence that the bike is in fact operating on all 4 at idle.

[mikenixon]

Whiskerfish -- You make a good point, that moving the screws in both directions gives one a good auditory clue that the idle circuits are in fact working properly. I would argue that you don't need the idle drop procedure to do that. And I hope anyone reading this thread will take special note of your 1.5 turn augmentation, which is exactly what I was saying. The procedure leaves the circuit far too lean. .

[Recycled Roadkill]

The procedure leaves the circuit far too lean. .

If I understand correctly "The proceedure" you're talking about here is Honda's and not Wiskerfish's?
I just needed some clarification on that.
BTW, I just finished reading the article that you linked to and learned enough to make me dangerous. As we've discussed before, messing with carbs, especially the GW carbs tend to make me rather nervous.

Concerning the XS650 carbs we'd discussed in PMs the prior month, this bike is exhibiting afterburn. Is this easily corrected by turning the idle screws out another 1/2 turn?

[mikenixon]

Yes, Honda's. And yes, richening the idle helps overcome afterburn. A little Alka Seltzer doesn't hurt either! :-P