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gener736
Samba Member
Joined: October 18, 2013
Posts: 2
Location: sebastian
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 Posted: Wed Apr 16, 2014 4:12 am Post subject: Duel carbs |
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have duel EMPI 40 on my 1776 engine, lot of back firing. One day runs great next day terrible. has new plugs, wires,pertronic ignition valves set at .05 cold
any ideas? |
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Letterman7
Samba Member
Joined: March 14, 2004
Posts: 3198
Location: Downingtown, PA
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| Posted: Wed Apr 16, 2014 5:04 am Post subject: |
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| EMPI carbs, intake leak, exhaust leak, running lean, clogged jets, clogged ports, clogged fuel filter, faulty Pertronix... did I miss anything? |
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Dale M.
Samba Member
Joined: April 12, 2006
Posts: 20380
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Wed Apr 16, 2014 7:20 am Post subject: |
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Usual conditions as you describe are cause by either vacuum leaks or clogged idle jets... Remove jets and can clean (shot of pressurizes carb cleaner) through them and do visual to see that they are clear (look through jet at light source) ... WEBER IDF and EMPI HPMX are famous for clogged idle jets, and its caused by dirt getting past air cleaners and into idle circuit air inlet on carb top....
If problem of clogged idle jets persists get better air cleaners and do better seal on air cleaner filter element to base, or get (or fabricate) Jet Doctors...
Dale
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wythac
Samba Member
Joined: August 02, 2004
Posts: 2791
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| Posted: Wed Apr 16, 2014 12:49 pm Post subject: |
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| Make sure they are "dualling" instead of "duelling". Linkage set up is critical. |
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didget69
Samba Member
Joined: July 22, 2004
Posts: 4927
Location: Raleigh, North Carolina
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| Posted: Wed Apr 16, 2014 5:54 pm Post subject: |
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I can add nothing of value to this post, other than 'bad fuel'?
Good Luck!
bnc
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Lo Cash John
Samba Member
Joined: February 06, 2004
Posts: 2246
Location: Jacksonville, FL
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| Posted: Wed Apr 16, 2014 8:04 pm Post subject: |
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Things to do and some questions:
Check for intake leaks
Did you CORRECTLY sync the carbs? "Good enough" doesn't cut it here.
Are the air filters oiled?
Apply a thin coat of grease to the rubber surfaces of the air filters. This will help stop sand from getting in above/below the filters.
What's the jetting in the carbs? Straight out of the box is very rarely right.
Does it idle on all 4 cylinders?
When driving, if you floor it what happens?
When floored, does it fire all 4 cylinders?
What kind of exhaust system do you have?
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slalombuggy
Samba Member
Joined: July 17, 2010
Posts: 9147
Location: Canada
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| Posted: Wed Apr 16, 2014 10:05 pm Post subject: |
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Did you take the carbs apart when you got them and check for dirt in jets and float bowls and make sure the float is set at the correct height? This must be done on any carb no matter who made it.
brad |
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