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 Post subject: DCOE Carb help? - Carb bogging down at acceleration
PostPosted: Sat Apr 02, 2011 4:21 pm 
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Joined: Mon Feb 22, 2010 7:33 am
Posts: 41
Location: Ohio
OK - so my Civic 1200 has a single weber 40 DCOE. It idles fine, but when I put my foot down, the engine bogs down and dies if I dont let up. If I very slowly press the accelerator I can get a fairly smooth acceleration with some slight "popping" in the exhaust, but nothing bad - but that is only if I do it VERY slowly.

All this is while I am in neutral. If I am driving, a similar thing happens, though it is a little worse. If I step on the gas the nose dives and if I dont let up the engine will die too.

My jets are 125s.

Any ideas where to start? I have a weber book but it isnt really helping. I didn't post this in the Honda garage because it isnt a honda issue (they didnt come with weber DCOE's!)


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 Post subject:
PostPosted: Sat Apr 02, 2011 6:39 pm 
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Joined: Thu Oct 04, 2007 11:17 am
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Location: Hope, British Columbia, Canada
what size chokes have you got in there? I have my dellorto 40's and had to pull the 34mm chokes in place of the 32mm's chokes as it was bogging too bad

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 Post subject:
PostPosted: Sat Apr 02, 2011 6:47 pm 
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Joined: Mon Feb 22, 2010 7:33 am
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Location: Ohio
Hey there Kurt....

I have no idea what size chokes. I got it with this engine and I know it used to work with this setup.

Will it say on the chokes if I pull them?


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 Post subject:
PostPosted: Sat Apr 02, 2011 9:14 pm 

Joined: Sun Apr 20, 2008 12:37 pm
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Location: Sugarhouse, Utah
I know nothing about that particular carb, but it sounds like an accelerator pump issue. just my .02

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 Post subject:
PostPosted: Sat Apr 02, 2011 9:47 pm 
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Location: Hope, British Columbia, Canada
avianman wrote:
Hey there Kurt....

I have no idea what size chokes. I got it with this engine and I know it used to work with this setup.

Will it say on the chokes if I pull them?


If it worked before its likely something else but yes if you pull them out they will be clearly marked

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 Post subject:
PostPosted: Sun Apr 03, 2011 4:05 am 
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Location: Sydney, Australia
Initial thoughts are that the chokes are too big, but also could be because you don't have enough ignition advance. Webers give quite a slug of fuel on tip-in and you need more advance at low rpm to deal with it.

Do you know what the distributor specs are? If say 8BTDC is stock timing you will find that 15BTDC will make a world of difference. But depending on your stock ignition curve, 15 degrees of base timing might be way too much at the top end, and you might need to get your distributor modified to dial it back at high rpm.

BTW The choke size is usually cast into it. You can juuust kinda see it at 5 o clock on the one on the left here. After you remove the air hornm they should be able to be wiggled out with your fingers.
Image

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 Post subject:
PostPosted: Sun Apr 03, 2011 10:06 am 
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Joined: Mon Feb 22, 2010 7:33 am
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I advanced the timing as much as I could and it seemed to have quite an affect! I can't tell the actual degree of advance as there arent numerical indicators on my engine. Still bogs a little but not as bad. Im going to keep playing with it and see...

I might lower the jets as it looks like the plugs are a bit fouled.


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 Post subject:
PostPosted: Sun Apr 03, 2011 2:40 pm 
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The way it works is that the idle jets are only in play until about 3000rpm (and by then they are gradually phasing out). So if you are having a stumble at about 3000rpm, then it's more likely an issue with your main jet or emulsion tube, rather than the idle jet.

Keep en eye on the ignition though, it might not tolerate so much advance at the top end, but also go over your ignition system carefully, renew the plugs, check your points gap, cap and leads. Basically if your ignition system isn't 100% it won't help.

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datsunfreak wrote:
No Kev, you are eating a duck fetus.


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 Post subject:
PostPosted: Sun Apr 03, 2011 4:52 pm 
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Location: Sydney, Australia
BTW, advancing it all the way probably isn't such a great idea, btw :)

Pull the jets, emulsion tubes and correctors and verify the size of your idle jets. Also you need to verify the size of the chokes, since the jet sizing is done relative to the size of the choke.

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No Kev, you are eating a duck fetus.


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 Post subject:
PostPosted: Sun Apr 03, 2011 6:02 pm 
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Location: Hope, British Columbia, Canada
I would pull your chokes first and foremost. I can almost promise if they are larger than 32mm they are overkill for the 1200.

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 Post subject:
PostPosted: Sun Apr 03, 2011 7:05 pm 
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Joined: Mon Feb 22, 2010 7:33 am
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Location: Ohio
No, i wouldnt leave it that way, but there is no pinging. The car is disassembled for paint so I cant road test it, but it does give me an idea of what might be wrong. If I there was no change in the issue (good or bad) after I advanced the timing, Id know that the timing wasnt an issue.

I really dont think the idle jets are the issue....it purrs like a kitten when idling and at low RPMs. I dont want to mess with that yet.


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 Post subject:
PostPosted: Sun Apr 03, 2011 8:05 pm 
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Location: Sydney, Australia
What sort of ignition system have you got? Is it points?

You might find that an upgrade to electronic ignition is a good idea. Points ignition gets its current thru a ballast resistor, which means that you're only getting about 6V instead of thr full 12V.

Upgrading to say a pertronix points free setup isn't expensive, and it will allow you to ditch the ballast resistor, which means a full 12V is used for sparks and you get a somewhat bigger zap.

If it's responding to ignition advance, then you may find that powering up the whole system fixes it.

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No Kev, you are eating a duck fetus.


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 Post subject:
PostPosted: Mon Apr 04, 2011 5:20 am 
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Joined: Mon Feb 22, 2010 7:33 am
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I have a petronix ignitor, though I am thinking Id like a better coil....not sure about how to do that correctly yet


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 Post subject:
PostPosted: Mon Apr 04, 2011 5:29 pm 
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Hey, complete threadjack, but I have a weber 45 DCOE. It is on my 76 Celica, 2189(20R) CC engine, no major mods except a header. Wondering if these values sound right to anybody.
Chokes are 34s. Idle jets are 55s and main jets are 145. Sound good? Sound too large? I am reading on tuning webers, but seems like a lot of numeric spagetti to me.
I do have an electronic distributor from an 84 22R that will shortly be installed.

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 Post subject:
PostPosted: Thu Apr 07, 2011 10:46 pm 

Joined: Thu Apr 15, 2010 12:30 pm
Posts: 21
Location: Orange County, CA
From my Weber Sidedraft book.
Not many shown since i focused on Datsuns but Honda Civic is there

Sorry for the Ginormous pic but it's a super high res scan.

Image


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 Post subject:
PostPosted: Fri Apr 08, 2011 5:45 am 
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Joined: Mon Feb 22, 2010 7:33 am
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Location: Ohio
I appreciate the scan, but I dont know what I'm looking at ....what are the letters at the top indicating?


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 Post subject:
PostPosted: Sat Apr 09, 2011 11:29 am 

Joined: Thu Apr 15, 2010 12:30 pm
Posts: 21
Location: Orange County, CA
Image


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 Post subject:
PostPosted: Sat Apr 09, 2011 11:53 am 
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Joined: Mon Feb 22, 2010 7:33 am
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Location: Ohio
Interesting....I am running 120 main jets and it is running rich (black tailpipe soot and black plugs) and the scan says to run 140's. I wonder if my ignition system is running right


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