The dreaded metering needle lever

[purdyite]

Saw something today I hadn't seen before. Worked on a friend's Stihl KM unit, cleaned the carb with the ultrasonic cleaner, but his worst problem was a stopped-up spark arrestor screen. Brought it back today saying gas was coming out the muffler and it ran terrible. I suspected the metering needle and sure enough it had stuck open! I haven't seen one stick like that--I had wiped the needle and seat when I went through the carb and everything seemed to operate smoothly. Anyone have one stick open before?

Which brings up another point--I have been very exacting when checking the metering lever ( I have the gauges), but I am beginning to think that setting it just a little low is better. If the diaphragm is stretched any at all, it could possibly cause a rich condition, and I tested this on my string trimmer. Setting it just a smidge low seemed to even out the idle, and even made accelerating smoother. It appears that setting it high is much worse than setting it a little low. What do you do--set it at exactly the contact point with the gauge, or leave it just a little low? I know that most of the time you don't have to mess with it, but to be thorough would dictate at least checking with with the gauge. Thanks for any insight on this. I feel like that little thing is significant in getting one to run properly.

 

[SteveSr]

Saw something today I hadn't seen before. Worked on a friend's Stihl KM unit, cleaned the carb with the ultrasonic cleaner, but his worst problem was a stopped-up spark arrestor screen. Brought it back today saying gas was coming out the muffler and it ran terrible. I suspected the metering needle and sure enough it had stuck open! I haven't seen one stick like that--I had wiped the needle and seat when I went through the carb and everything seemed to operate smoothly. Anyone have one stick open before?

Blindly throwing an otherwise working carb into a sonic tank is just asking for trouble. The sonic tank may loosen up all sorts of crud that may migrate to other places (like the needle seat) and cause new issues.

 

[Vintage Engine Repairs]

I set them to spec height. I have discovered the more creative I get the more problems I introduce lol

 

[LegeaDejului]

Blindly throwing an otherwise working carb into a sonic tank is just asking for trouble. The sonic tank may loosen up all sorts of crud that may migrate to other places (like the needle seat) and cause new issues.

I think whatever comes loose will be flushed out with some pressurized carb cleaner and some needle brushes. If I take it apart, I’d rather clean it perfectly than leave it be and have another ticking bomb issue just around the corner.

 

[Pioneer]

I set to spec height. Had one valve stick open because of a stiff diaphragm.

 

[stihltech]

More trouble than they are worth to rebuild due to such issues. Replace them and carburetor problems disappear with no comeback.