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Hanging idle please help

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K2-K6:
Adding some additional checks to the list;-

Check that the ignition advance retard mechanism is working and drops back to baseline as revs drop ( probably worth removing and checking for operation if not sure of condition) as advance timing will certainly promote higher idle speed.

Same as you Alan,  in that it doesn't appear like jetting as that is usually consistent. Either right or wrong. But uncontrolled revs are nearly always a scource of air that you aren't able to control.  With that in mind,  the intake head to carb rubbers are one of the prime suspects here, even if they look ok.  Plus the clamping bands have to have good integrity to both fit in their groove and clamp to eliminate 100% of any potential leaks.  If they are either very hard or you've any doubt about them,  then a spray around them with carb cleaner (sparingly with tank removed and outside as it's a flammable risk) will ordinarily show you.

Specifically an air leak must be between the carb slide and the combustion chamber to achieve uncontrolled throttle effects,  just to add a clear problem statement. 

Another "potential" scource, if all of the above posts don't effect a cure. If you can get it to "hang" while stationary,  place the engine breather pipe into a clear bottle (small plastic water bottle) with some engine oil to submerge the pipe,  and closely monitor the level while revving and closing the throttle,  it shouldn't suck the oil level to a lower position. 

Wenman:
https://youtu.be/wTdmuhMUE1Y

Okay so I think I’ve found the culprit.. you were correct in that the sliders aren’t seating properly.
If I blip the throttle the Return spring and Weight pulls them closed.

If however I slowly open the throttle to say 2500 revs and let go they struggle to fully seat and remain open about 2-3mm. They do slowly go down which can be seen in the last 3 throttle pulls in the video.

What could remedy this? I believe the cables are adequately routed with no sharp bends. Could it be a fault internally inside the carbs bent needle or faulty slider.

Any recommendations would be helpful thanks guys!

Alan

JezzaPeach:
Could it be slides gumming up? Mine did when I left it for a long time. I sprayed GT85 or similar via the air box which seemed to help and use Sta-Bil in the fuel.

Wenman:

--- Quote from: jeremypeachey on July 13, 2020, 11:50:46 AM ---Could it be slides gumming up? Mine did when I left it for a long time. I sprayed GT85 or similar via the air box which seemed to help and use Sta-Bil in the fuel.

--- End quote ---

Worth a try.. I just sprayed them with gt85 and it didn’t revolve interestingly it does NOT do it when the engines off!!!
So whatever is causing it is a result of what’s happening when the engine is running!!

Please help 😂

JezzaPeach:
Can you hear the slides metallic click as they hit bottom?

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