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> Carb question
last337
post Jan 6 2013, 05:57 PM
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Hello everyone! I got my new EMPI 40s on yesterday and I have been going through the adjustment all day today. It has been a long time since I have messed with carbs and Im not sure if I am doing this correct.

Initially I got my linkages all set up and correct with the speed screw at about 1 turn in. I have all the air bleed screws all lightly seated and mixture screws about 1 1/2 turns out.

At this point it is very rich but runs well at an idle of about 900 and actually comes up really nice but is smoking and even spitting out fuel from exhaust. I figured at this point I could begin going in 1/4 turn at a time on each mixture screw to the point the engine starts to run rough then back a 1/4 turn. I did this on all and it was still smoking badly. I havent set timing or anything like that but I would assume the only electrical issue (am I wrong?) that could cause rich conditions at idle would be a fouled plug but it is running smooth and not as if it is missing with a fouled plug.

I am wondering if maybe I should go another half turn on the speed screw then see if I can go in further with the mixture screws. Is there anything I can do with the air bleed to adjust this? I thought they were only adjusted for syncing and not for a rich condition.

The vendor I got them from claims they have the following jets:
52 idle jets
115 main jets
200 air jets
28mm venturi
550 EX. pump jets
50 accelpump jets
F11 emulsion tubes

Am I oversized with that I have in there now? I have been reading the following link to troubleshoot and it says if I am over 1 1/2 turns in on mixture then my jets are too big. The problem is that I cant get it to run at under 1 1/2 turns on mixture. However, maybe I should try another half turn on speed screws?

Any help is greatly appreciated (IMG:style_emoticons/default/biggrin.gif)
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rhodyguy
post Jan 7 2013, 04:15 PM
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thomlinson (cb perform book) suggests setting the by-pass at 1/2 turn off closed for the initial setup. a 40 i'm looking has 50s for the idle jets. 52 might be a tad fat and you cut some air off the idle mixture when you closed the by-pass. open all 4 up 1/2 a turn and see what happens. if the idle circuit is rich to begin with and the engine is idling a lot when you're adj the carbs you'll be loading the plugs up with carbon. if your unregulated facet is over driving the fuel float needle valve you''ll in a rich condition all the time.
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last337
post Jan 7 2013, 07:21 PM
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QUOTE(rhodyguy @ Jan 7 2013, 04:15 PM) *

thomlinson (cb perform book) suggests setting the by-pass at 1/2 turn off closed for the initial setup. a 40 i'm looking has 50s for the idle jets. 52 might be a tad fat and you cut some air off the idle mixture when you closed the by-pass. open all 4 up 1/2 a turn and see what happens. if the idle circuit is rich to begin with and the engine is idling a lot when you're adj the carbs you'll be loading the plugs up with carbon. if your unregulated facet is over driving the fuel float needle valve you''ll in a rich condition all the time.


Thanks for the help! I realized two things. By backing out the air bleeds I was definitely able to lean things out a bit although at this point they are almost seating completely again. Secondly, I was trying to do my adjustments with the engine way too cold.

At this point I have a 'somewhat' smooth idle but I hear a popping/sucking sound from the carbs at times. Under the load there is a bad hesitation coming off idle and you can hear the carbs almost start to whistle as if they are starving for air after the hesitation goes away. Any ideas?
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Posts in this topic
last337   Carb question   Jan 6 2013, 05:57 PM
vw505   Did you clean and adjust the floats before install...   Jan 6 2013, 08:52 PM
last337   Did you clean and adjust the floats before instal...   Jan 6 2013, 09:17 PM
Trekkor   The only real adjustments are going to be with jet...   Jan 6 2013, 09:33 PM
last337   The only real adjustments are going to be with je...   Jan 7 2013, 06:41 AM
Wegeng_Haus   The only real adjustments are going to be with j...   Jan 7 2013, 12:38 PM
bperry   What about fuel pressure? The stock fuel pump cre...   Jan 7 2013, 01:36 AM
last337   What about fuel pressure? The stock fuel pump cr...   Jan 7 2013, 06:37 AM
last337   Thanks for the info! Today I started pulling ...   Jan 7 2013, 02:24 PM
rhodyguy   opening a air bleed screw allows air to enter that...   Jan 7 2013, 03:33 PM
last337   opening a air bleed screw allows air to enter tha...   Jan 7 2013, 03:50 PM
rhodyguy   thomlinson (cb perform book) suggests setting the ...   Jan 7 2013, 04:15 PM
last337   thomlinson (cb perform book) suggests setting the...   Jan 7 2013, 07:21 PM
ThePaintedMan   thomlinson (cb perform book) suggests setting th...   Jan 7 2013, 09:59 PM
last337   Thanks for all the input. I am on Pelicanparts to...   Jan 8 2013, 10:02 AM
FourBlades   My brand new set up and shipped to my door carbs h...   Jan 7 2013, 07:49 PM
Trekkor   These are dual 2bbl's right? One throat for ea...   Jan 7 2013, 10:20 PM
rhodyguy   Bob Thomlinson's Weber Tech Manual avail thru ...   Jan 8 2013, 10:20 AM


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