Hanging idle going to stall, NOT carbs. Need ideas.

[bobgroger]

I now know a lot more about what it is NOT. Still looking for the cause but I need to take a couple days off to clear my mind. I am pretty much down to Dyna or jumped cam timing, although it runs so well above 2k. I have a Dyna on another bike, so that may be next.

[bobgroger]

I wanted to update this in case someone stumbles on it in the future. It WAS the carbs, and I feel like an idiot. However, it was NOT too lean, it was too rich. I had that fleeting thought early on, but dismissed it. It ran fine with the 4-1, the stock exhaust has more backpressure = richer. If the idle circuit is too rich, you have to increase the idle speed to keep it running, which uncovers more of the 3 ports under the butterfly. Once you do that the mixture screw really doesn't have much effect. I pulled the plugs after idling for a while, #1 was black and 2-4 were darker than normal. Looked at #1 and found the mixture screw when turned in was stopping on boogered threads instead of bottoming out. I carefully coaxed it in another 3 turns or so. I also changed the pilot air jets from 170 to the correct 160. Turned the mixture screws out 4 turns and slightly better, but not right. Turned the screws in gradually to about 2 turns which sped the idle up enough to turn down the main idle screw to ~1200 and it is steady as a rock. This may or may not be factually correct, but it explains it pretty well: http://www.mychinamoto.com/forums/sh...y-re-different . Moral of the story, hanging idle with CV carbs can be too rich as well as too lean. A WB AFR meter is on my list.

Glad to have this finally sorted, a great learning experience and the new owner picks it up Sunday. But he is bringing another GS trade.....