Northy
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 posted on 25/4/04 at 06:48 PM |
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Engine won't idle
Tried to get my car running again today, was planning first drive but...
It won't idle. I've fitted a brand new (don't ask!) pair of twin 45 Webers, and tried to adjust them for idle as told to in my carb
book (can't remember name). But it will not idle at all with the butterflies shut, no matter how the idle screws are set. Any ideas before I
trialer it somewhere for them to do it!
Cheers
Graham
Website under construction. Help greatfully received as I don't really know what I'm doing! 
"If a man says something in the woods and there are no women there, is he still wrong?"
Built 2L 8 Valve Vx Powered Avon
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britishtrident
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| posted on 25/4/04 at 06:59 PM |
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The 40 dcoe has no butterfly by-pass so the butterfly idle speed screws need to be given a few turns.
Clean and check the idle jets and try again.
[Edited on 25/4/04 by britishtrident]
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Northy
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| posted on 25/4/04 at 07:10 PM |
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They're 45's, are they the same?
Will they still need cleaning if they're new? 
Graham
Website under construction. Help greatfully received as I don't really know what I'm doing!
"If a man says something in the woods and there are no women there, is he still wrong?"
Built 2L 8 Valve Vx Powered Avon
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novarallycar
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| posted on 25/4/04 at 07:19 PM |
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does it run and die ie it idles and slowly falls off? if so and you are at max adjustment on the idle bleed screws you need to go up a size (talk to a
webber agent they will keep you righht on sizing) if it is rich to the point of not running at idle you need to go down or crew the adjsters in if
more than 3 turns from screwing up tight you will need to decrease a size.
HTH
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ady8077
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| posted on 25/4/04 at 07:49 PM |
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Hi
Have your carbs got the fuel enrichment on the back? If so try attatching a choke cable or bit of string and open them slightly, if it'll idle
then you'll probably need to go up a size on your idle jets
Adrian
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Northy
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| posted on 25/4/04 at 08:29 PM |
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I got it to idle once, but only with the butterflies open a bit, so it would have been taking fuel from the main circuit (I think). Should the
butterflies be fully closed or slightly open?
What is max adjustment on the idle screws? How many turns?
Yeah, they've got manual fuel enrichment dodabs on, I've got a choke cable but its not connected. I'll give it a go.
Thanks for all the suggestions so far,
Graham
Website under construction. Help greatfully received as I don't really know what I'm doing!
"If a man says something in the woods and there are no women there, is he still wrong?"
Built 2L 8 Valve Vx Powered Avon
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Dave Ashurst
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| posted on 26/4/04 at 10:11 PM |
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Northy
I don't think there's anything wrong mate. If they are anything like my old DCOE 40s they simply don't idle with the butterflies
shut!
This is what I do to set mine up:
With the engine off, use the adjustment screw on the throttle linkage to get the butterflies balanced visually as best you can. i.e. both carbs
opening and closing at exactly the same moment. Peep down the inlets. It's good enough to get going with.
Then screw all the idle jets in fully (gently), then unscrew them all by exactly the same amount; about 4 or 5 half turns each won't be a mile
out.
Start the engine and adjust the throttle stop screw to get a reasonable idle speed.
Then balance the carbs with the linkage adjuster, preferably using an airflow meter or, if you're good, by ear.
Then you can adjust the idle jet screws to optimise the idle speed. It's fiddly because there's 4 to adjust and it's not an
instantaneous effect - that is, you have to wait a few secs after each adjustment. Also you'll probably have to reduce the idle speed back with
the throttle stop screw as you go along, otherwise it'll rev too fast and might start to involve other jets and stuff.
Depending on cam profile and assuming your igntion timing is correct you should easily be getting a reasonably smooth idle around 800rpm and, as they
say, years of motoring pleasure.
However, if you unscrew the throttle stop/idle speed adjuster so that the butterflies close completely then the engine will stop. But that's a
good sign. It means there are no air leaks!
hope that helps
regards
Dave
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