Stalls running at idle speed

[MattFL]

Just another thought... on the idle mixture screw. If the TAB is the only thing holding the screw from turning completely out, then I'd see if it's possible to just grind or file the tab off without having to remove the complete cap.

They're really fragile, I think they're designed to pop off easy, as in break the head off the screw easy. When I took them out of my motor they broke off super easy.

It looks like Honda sells replacement kits for at least some motors. Check on the parts list for that specific motor, and if the replacement is available then it might be worth the few bucks to not have to spend all the time being careful.

 

[kyounger]

Pulled the idle mixture screw out, cleaned inside, replaced and after many many attempts to keep it idling it continued to fail, regardless of the adjustments to the mixture setting and idle speed setting.

Time for a new carb????

 

[km1125]

How long did you soak it? I've had a couple carbs over the years (one Honda and one Tohatsu) where I had to do an overnight soak to finally get them running right. One of them I had soaked a couple times for several hours and thought "that oughtta do it!", but it still didn't work right. I started down a rabbit hole of looking for something else wrong in the engine before I went back and soaked the carb overnight and that is what actually fixed it.

Some of the "carb soak" stuff you get nowadays is pretty docile compared to what you could get years ago. That old stuff would work in hours but the newer stuff won't.

There are a couple of different passages that are used for "less than wide open" operation. There's the actual IDLE passage, that's regulated by the idle mixture screw, there's a "just off idle" passage that operates when the throttle is barely cracked open (but still provides a touch of fuel at idle) and a midrange passage that covers up to about 25% throttle. After that, it's mostly the main jet and venturi that's regulating the fuel. Those smaller passages are almost always a problem on smaller engines.

 

[ahicks]

Pulled the idle mixture screw out, cleaned inside, replaced and after many many attempts to keep it idling it continued to fail, regardless of the adjustments to the mixture setting and idle speed setting.

Time for a new carb????

This was AFTER you pulled the center tube and confirmed it was clear by the fact you could see through the bore? Not talking about the tiny holes in each side. I'm talking about the jet located INSIDE that tube. If this step is skipped you've fixed nothing....

Next most important is the tiny tiny o-ring at the top of that tube. If it's nicked, hardened or otherwise damaged, there will be no fuel supplying the low speed system.

I would NOT depend on any kind of soak. You'll be far further ahead confirming each passage is open visually if possible, or by shooting compressed air or carb cleaner and getting a solid flow through the opening....

 

[km1125]

Here's another thought too... looking at the parts diagram in post #14 (is that your actual carb?) It looks like there might be passages in the bottom of the bowl. I had a Tohatsu carb similar to that and the passage in the bottom of the bowl was blocked. On that engine, that passage fed a reservoir that provided fuel for the "Bystarter" (choke) and the idle circuits. The engine would run great wide open but have trouble starting and idling until I cleaned that circuit in the bowl. Easy enough to check if your bowl has that and if it's clean (spray through it but avoid having it shoot back into your eyes!).