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directordanw

Revving REALLY high

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Evening all.  Spent a frustrating day trying to tune the carbs but keep on coming up against the same problem - however I set the idle screws as soon as the engine reaches temperature the revs shoot up to 2k at idle and the only way to bring it down is to seriously retard the timing - like by 7 or 8 degrees which plays havoc elsewhere in the curve.  The carbs were rebuilt recently, the jets are apparently spec for the 2.2 and there's no vacuum leak I can find.  And the floats have been set and reset.  The one oddity is that when the throttles are closed the throttle adjusting screw doesn't reach the lever, even when it's fully screwed out there's still a gap.  And that's not right!

 

What am I missing?!  I don't mind someone telling me I'm being dumb as long as someone can help me get this sorted!

 

Thanks in advance, Dan

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Upgrade today to remove Google ads and support TLF.

Almost embarrassed to ask such a basic Q, but have you had the airbox off to confirm that the butterflies are closing fully? With the adjusting screw not reaching....

Dave

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Don't be embarrassed! It's me who's probably being an idiot! But yes, the air box has been on and off all day. And as far as I can see the butterflies are fully closed - that's without removing the carbs again. If there was an air gap what could be preventing them closing? Any ideas?

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Not sure it's even possible, but accidentally refitting one of the butterflies the wrong way around would hold the other open.

Have you got a vacuum guage to check across all the inlets?

Are you setting the idle with the cable disconnected to remove any influence the cable may be having on your problem?

Edited by Simon350S

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The fact that the adjusting screw doesn't seat correctly would make me think mechanical interference somewhere rather than just an air leak, but as Simon says, have you vac balanced them?

Did you rebuild em yourself, or are you relying on someone else's info that the jets/ floats are correct. What do you now have fitted?

Any chance of a couple of pics...I'll bet someone on here will spot if anything isn't right.

Final thought for now, the choke mechanism isn't interfering somehow is it?

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Thanks guys.  The only vacuum gauge I've got is an ancient Carbalancer - and it's never been very reliable, even when new.  If you can recommend a better alternative I could really use one.

 

The carbs were rebuilt by myself last year - new springs, washers, gaskets - after an ultrasonic clean.  And I set the float levels then, and again yesterday.  The butterflies never came out during that process so are all as were.  As for the jets themselves I am saying they are spec simply because I returned the original jets the carbs after cleaning.  So that is an assumption that the carbs were spec before I got hold of the car... I will pull the idle and main jets and check them, and post some photos today.  For clarification on a 2.2 Eclat the carbs are spec 9 with a main jet 160 and the idle being 58?  I am trying to set them with no cables attached.

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In the absence of a proper airflow meter, Use a length of flexible plastic pipe like a crude stethoscope, you will be able to hear airflow differences/imbalances. With a bit of practise you'll be able to set carb balances quite accurately. This tube is also handy to listen for airleaks around the manifold, you'll hear and be able to pinpoint the sucking sound.

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Hi. Have you checked the throttle return spring is there and not broken. It connects between the airbox and carb linkage.

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Return spring is there, although not when the box is off of course.  I could probably do with a new one, but even when I close the throttle by hand I can't get it to meet the adjusting screw.  Which suggests a mechanical snafu somewhere.  

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Hi. Are the carb butterflies physically synchronized with each other? The easiest way is to remove the progression hole covers with the engine NOT running.(the large brass screws on the barrels) and shine a light down them. You will see a shallow well with 3 or 5 tiny holes. Make sure the throttle stop is screwed out, so the lever doesn't rest on it. As you open the throttle you'll see the butterfly plates move past the progression holes. Using the balance screw on the linkage between the two carbs, make sure the four butterfly plates are level they should rest just to the manifold side. If the butterfly plates don't line up on the same carb, the shaft is twisted.

Hope that makes some sense

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Sorry should have said. The progression cover is the large brass screw on the barrels next to the mixture adjustment screw. Cheers j

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Thanks, that makes perfect sense. I will check that today. And post some photos. Assuming it's not chucking it down again!

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So, finally got out this morning and checked the progression holes - and they're all over the place.  I'm assuming that when the butterfly opens it should slide past all six of the holes?  On the left carb it only appears in the bottom hole when closed, and then moves away when opened.  And on the right one it covers the bottom three.  This suggests to me that the butterflies are always open, even when 'closed'.  Does that sound right? So they're coming off and getting rebuilt.  Again!

 

Another suggestion from Terry was that the cold start system might not disengaging entirely so I opened these up and the piston valve seems to be free.  Just wanted to ask if anyone used any kind of lubrication on these pistons?  Before I close them up and forget about them again!

 

Thanks people!

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I cannot remember off the top of my head how the carbs connect, but is it possible the mechanism that links the two throttle shafts together is set wrong so one closes before the other and holds it open? Can you disconnect them in situe and let them operate independently as a test?

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Thank you Wilf, thank you everybody! That is exactly what had happened. It was as simple as lining the butterflies up through the progression holes. Des Hammill's book says wind off the linkage adjusting bolt until there's no contact. But actually when I did this one of the carbs was left fractionally open. It wasn't until I adjusted this so all the butterflies were in line that the revs settled down to a steady 900rpm with the timing set at 9 degrees BTDC. I say steady, it's still a bit lumpy, but at least I can tune it now. Once again the Forum saves the day. Thanks all.

This them brings me to my next problem. One of the idle screws is starting to lose its top, but I can't get it out of the carb body. It needs replacing before it's totally shredded and I'm at a loss as to how to shift it. I don't want to drill it, too much opportunity for disaster but it's got to be changed. Any brilliant ideas???

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I had this problem on my first Esprit & managed to get it out by removing the carbs to the bench & using a flat screwdriver bit in an impact driver, be careful though. :shock:

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