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Old December 20th 04, 09:16 PM
Gareth Edwards
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"dave" > wrote in message
...
> >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)


Adjusted valves, still same problem. Pulled the plug wire and the engine
note is the same. Also shorted the plug wire to ground to check for spark,
so I'm thinking it must be something to do with the carb (or at least one
side of it).

There are separate vacuum ports for each throat, I will try and compare the
vacuum a.s.a.p., along with testing the carb for leaks with some carb
cleaner. Am I right in thinking that when you spray this around the base of
the carb, the engine will pick up if there is a leak present? Or is it just
a visible thing i.e. will I see it bubbling around the carb seal?

Thanks Dave


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