Idle speed and mixture help 2.0 cu

[diesel11]

I sent the carbs away about 2 years ago to be reconditioned, is there a possibility they didn't set the bottom butterfly to the correct gap do you think,bits always idled a little bit high but seems to be more obvious since I have changed the distributor


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[ajsimmo]

One explanation for increased idle speed is that you've swapped to an svda dizzy. The dual vac retards the timing at idle by 12°, putting it back to 5°ATDC. This lowers the idle speed considerably. It can be very tricky to get the idle down with too much advance, and this can be made much worse if your ported vacuum signal from the left hand carb isn't shutting off at hot idle. It only needs to be held slightly open by tension in the linkage or resting on the choke, and it'll advance the timing and raise the idle. The other mistake a lot of people make is setting the carbs too rich. They should be really leaned off, and let the idle circuit do more of the work, so the idle air screw is 2 or 3 turns open and really sucking, and the idle fuel screw actually does something!

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[bigherb]

Excuse my ignorance, so you are saying there should be a gap on those throttle stops while the choke is "on" then when the engine is up to temp the throttle stops should be in the position they are now?

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Yes when the chokes are on the there should be a gap between the screw and the stop, chokes off the screw should sit against the stop.

[diesel11]

Right, looks like I'm going to have to take the carbs off, and see if I can get my head around setting the bottom butterfly gaps properly, then set all the adjustment screws to a "basic setting" and go from there? I've got another vacuum gauge coming in the post which should read both carbs together, is there a specific air flow I should be seeing at certain rpm's?

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[ajsimmo]

... is there a specific air flow I should be seeing at certain rpm's?

No, as long as they're (as close as possible to) the same.

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[diesel11]

Thanks for the replies, I'll be taking the carbs off tomorrow, and seeing if I can get my head around them ( head in my hands ) I'll post up if there's anything I can find out and let you know what happens

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[diesel11]

Just a quick question, sorry to keep on. The left hand carb, with the two idle speed screws, purple and white arrows on my previous pics, is there a base setting for these? Or is it like the fuel /air mixture screw on the bottom of the carbs, 2 1/2 turns too start with, can't seem to find much info on those? Think I've got my head around the settings for the bottom butterfly thanks again

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[ajsimmo]

Not as such - it depends on several factors, not least manifold vacuum at idle. It's most important that you have no air leaks on the idle circuit. That hose visible in your pic looks too loose, for example. All those joins need to be airtight, or each leak is leaning off the mixture.
You need the carbs to be doing about a third of the work each, and the "third carb", the idle control, doing the third third, if you follow. So when you pull the solenoid feed wire off each carb the idle drops to a slow lumpy almost stall idle, and does the same each side. When the feed wire is pulled off the idle solenoid it should struggle to run. If it stays fairly smooth, your carbs are doing way too much of the work, and therefore the idle circuit isn't doing much at all, and that's why the idle fuel screw makes little or no difference.

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[diesel11]

I think I follow, I'm going to replace the rubber sections of the vac pipes and balance pipe, the elbow sections are all good less than 12 months old, I think the biggest hurdle I've got is to get those butterflies in the right place but see how it goes fingers crossed

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[diesel11]

So I've set the bottom butterflies as in sarran's demo, I've set the idle jets to a " midway" point ran the engine up to temp, disconnected each idle clave, until there's a noticeable change in rpm( the right hand carb nearly cutting out, connected the vacuum gauges left hand gauge all over the shop on idle, right hand gauge steady 0 on the vacuum, co@ 2.1 ish turned the left hand idle/air mixture screw slightly, turned the right out slightly brought the revs to around 3000 both gauge's reading approximately the same, co now reading 3.14 approx , idle speed around 860/900, idle speed the right hand carb back down to 0 left hand carb all over the place again, idle speed when the distributor vac pipe re attached goes up to around 950/1000 rpm but engine seems to rev alot smoother, does that sound about right to you guys?

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[diesel11]

I've tried to upload a video to try and demonstrate it abit better//cloud.tapatalk.com/s/5ea1f873394 ... 171417.mp4

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[ajsimmo]

What's a clave?
No mention I could see of adjusting the actual idle circuit!? Are you just getting the carbs balanced first before doing that?
And connecting the vac hose should have no effect on idle speed, as no vac signal should be present at idle. If there is, your throttle butterfly isn't closing fully.

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[ajsimmo]

Don't know if you've read this? It's written about a bay, but the setup is just the same. Except without the retard function, you'll struggle to get the idle down to 850rpm.
https://forums.kombiclub.com/threads/du ... ure.45512/" onclick="window.open(this.href);return false;

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[diesel11]

God knows what a clave is , valve is what it was meant to say, so looks like the left butterfly gap is too big?

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[diesel11]

Hoo ray, finally sorted it, bottom butterflies causing my issues, thanks for that last link set up the carbs to near as damn it the instructions, set the idle air flow so as when you pull the solenoid wires off it practically stalls, set the co to 3.55,(via the small screw on the top of the left hand carb) connected the two carbs up via the link set the carbs up to near identical, ( no vacuum at idle on the left carb) idle speed is around 900/950, co 3.5ish picks up when you rev the engine no coughing or spluttering, happy as a pig in muck, thanks for all your help and advice,always greatfully received, see what she's like down the road and how it starts first thing.

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