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Demon 650 tuning by TD37
Started on: 09-17-2007 10:58 PM
Replies: 8
Last post by: Russ544 on 09-18-2007 05:44 PM
TD37
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Report this Post09-17-2007 10:58 PM Click Here to See the Profile for TD37Click Here to visit TD37's HomePageSend a Private Message to TD37Direct Link to This Post
Hey everyone. Just put on the new Demon 650 ZZ4 carb I got off of ebay onto my warmed up ZZ3 in the SS. I went through it when I got it and replaced gaskets checked jets and what not. Everything was in order and looks like it hasn't been changed from factory specs. I fired it up tonight and I can't get it to idle down. The throttle cable is disconnected, the idle stop screw is all the way out, and the choke is open. Fuel pressure is just under 7 psi with a return regulator and the damn thing won't go down below 1500 rpm idle. If I lean out the 4 corner idle to a 1/4" turn out it will come down to 1000 but it stalls when you crack the throttle plates since it is way too lean. My carb does not have the Idle-Eze in the middle. It must be an older one without that feature. I know I've seen a couple of V8 guys with Demons on top. I need some help here. Anyone?

-Tim
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Arns85GT
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Report this Post09-18-2007 10:24 AM Click Here to See the Profile for Arns85GTSend a Private Message to Arns85GTDirect Link to This Post
This site will probably help. If you join, there are a pile of guys who know Demon carbs.

Good luck

http://www.hotrodders.com/f...highlight=Demon+carb

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Taijiguy
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Report this Post09-18-2007 01:45 PM Click Here to See the Profile for TaijiguySend a Private Message to TaijiguyDirect Link to This Post
Vacuum leak.
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FIEROPHREK
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Report this Post09-18-2007 02:36 PM Click Here to See the Profile for FIEROPHREKSend a Private Message to FIEROPHREKDirect Link to This Post
Do you have vacuum or mech secondaries?

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Formula88
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Report this Post09-18-2007 02:42 PM Click Here to See the Profile for Formula88Send a Private Message to Formula88Direct Link to This Post
Is the 7 psi high? I was thinking carbs took about 4.5 psi.
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Arns85GT
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Report this Post09-18-2007 02:52 PM Click Here to See the Profile for Arns85GTSend a Private Message to Arns85GTDirect Link to This Post
Holleys take 4.5 to 7. I run 6psi on mine. Of course flow is the other thing. The size of the fuel line makes a difference. If your engine has a big appetite, you might want 5/16's line.

Arn
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Erik
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Report this Post09-18-2007 03:00 PM Click Here to See the Profile for ErikSend a Private Message to ErikDirect Link to This Post
Other than a vacuum leak elsewere
Make sure all unused ports on the carb are plugged and you PCV valve is working correct
If I am not mistaken a demon uses holley parts and is set up the same way
If so then I would check that the secondary butterflies are not open too far at rest possibly causing a lean condition at idle
there should be a set screw on backside of the carb but most likely you wil have to remove the carb to set the screw .its that way on a Holley..other than that
your off idle stumble could be as a result of not enough of a shot of fuel from the acel pump which would mean stepping up the cc's of the pump and or adjusting the acelerator pump cam profile, pump squirter size on the primary throttle

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flames4me
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Report this Post09-18-2007 04:27 PM Click Here to See the Profile for flames4meSend a Private Message to flames4meDirect Link to This Post
Demon recomends 9 psi for most of their carbs.

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Russ544
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Report this Post09-18-2007 05:44 PM Click Here to See the Profile for Russ544Send a Private Message to Russ544Direct Link to This Post
vacume leak
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