>From: "Gareth Edwards"
>
>Hi
>
>Trying to set the idle screws on the carbs the other day, and I adjusted all
>of them apart from one. The idle screw for number three cylinder does not
>affect the engine at all, no matter how far I screw it in or out. I checked
>the idle jet, which I thought maybe blocked, but it is fine. What could the
>problem be?
>I have also noticed when the engine is idling, it sounds as though it is
>missing, and it is the same under light throttle. But when I put my foot
>down it picks up and goes great. Have I got a blockage somewhere in the
>idle circuit? What can I do to remedy this?

Might be a vacuum leak at the base of the carb. Some people will use carb
cleaner spray and spray at the base of the carb to see if maybe there is a
vacuum leak. Others use a gas like propane and aim it near the base of the
carb.
Both are done with the engine running and done carefully!! I have never tried
the propane gas method. <g>

Does your Dellorto have separate vacuum ports for each throat? If so then check
the vacuum on that port and compare with the others.
If not then there is a carb balance tool that measures vacuum at the top of the
throat of the carb.
Some use a hose holding one end to your ear and the other end over the throat
then listen and compare with the other throats.
Pull that plug wire to see if it makes any difference in the running of the
engine.
Adjust valves, do a compression check and report results here.

Hope this makes sense! <g>

later,
dave
(One out of many Daves)