Jet sizing...working on the carb....Lars plz step in I'm using your paper.
03-15-2004, 06:54 PM
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Jet sizing...working on the carb....Lars plz step in I'm using your paper.
Okay I finally pulled the carb.. I'm hoping getting it dialed in will help with some other probs...I'm gonna do it by lars' papers..
here is my set up
it's a speed demon 650 mechanical no choke.
I'm running a 383 10.5ish :1 around 500 lb/ft..I am running super rich right now..I'm gonna do all the things in Lar's papers...but I don't see anywhere how to determine jet sizing...
here is my set up
it's a speed demon 650 mechanical no choke.
I'm running a 383 10.5ish :1 around 500 lb/ft..I am running super rich right now..I'm gonna do all the things in Lar's papers...but I don't see anywhere how to determine jet sizing...
03-17-2004, 05:20 PM
#3
Race Director
Re: Jet sizing...working on the carb....Lars plz step in I'm using your paper. (munday)
Can't.
He doesn't say when the carb's running rich and/or how he thinks this is so.
Need details, man.
Otherwise, just put 75s in the primaries and 86s in the secondaries.
He doesn't say when the carb's running rich and/or how he thinks this is so.
Need details, man.
Otherwise, just put 75s in the primaries and 86s in the secondaries.
03-17-2004, 11:54 PM
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Re: Jet sizing...working on the carb....Lars plz step in I'm using your paper. (The Dude)
i think that's what i hat....78 and 86, i jetted down to the stock on the demon...70 and 78. I know i am running rich because my exhaust stinks like fuel horrible and I foul plugs every 20 miles. I can foul the plugs at idle.
03-18-2004, 01:31 AM
#5
Safety Car
Re: Jet sizing...working on the carb....Lars plz step in I'm using your paper. (munday)
i think that's what i hat....78 and 86, i jetted down to the stock on the demon...70 and 78. I know i am running rich because my exhaust stinks like fuel horrible and I foul plugs every 20 miles. I can foul the plugs at idle.
03-18-2004, 08:48 AM
#6
Safety Car
Re: Jet sizing...working on the carb....Lars plz step in I'm using your paper. (munday)
First, you need to get the idle circuit tuned right, then move on to the main circuit. If you're running rich at idle, get larger idle air bleeds or put small wires in the idle circuit of the metering block. Tune for a max vacuum on a gauge.
After you get the idle circuit right, move on to the main. This is where you shuffle jets. Best way to determine rich/lean conditions is with an air/fuel gauge plugged into your exhaust. If you don't want to do that, then good old plug reading will suffice. Read the tuning paper very carefully. 99% of what you need to know about tuning is there. They helped me tune my Holley 850 DP.
Brett :thumbs:
After you get the idle circuit right, move on to the main. This is where you shuffle jets. Best way to determine rich/lean conditions is with an air/fuel gauge plugged into your exhaust. If you don't want to do that, then good old plug reading will suffice. Read the tuning paper very carefully. 99% of what you need to know about tuning is there. They helped me tune my Holley 850 DP.
Brett :thumbs:
03-18-2004, 10:02 AM
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Re: Jet sizing...working on the carb....Lars plz step in I'm using your paper. (munday)
munday -
First, oput the carb back to its bone-stock jetting specs. Rich running at idle is usually caused by the throttle blade angles not being set up right. Do the bench setting as outlined in my paper once you have the stock jets back in it: et those primaries and secondaries cracked open to expose .020" of the transition slot on bot pri and sec throttles. Then, turn all 4 mixture screws 1 turn out from lightly seated. Once you get the thing started up, keep the pri and sec idle speed screws adjusted equally and run the float levels to the lower line on the sight glass. Fine-tune the idle mix screws after it's fully warmed up - you may find that it idles best at about 3/4 turn on the screws.
Either way, the stock jetting on a 650 should not run excessively rich if the carb is adjusted right. At most, you may have to change jet sizing by up to 2 sizes. Anything beyond 2 sizes is a possible clue that you have something else that needs to be looked at.
If you can't get it dialed in, send it out to me and I'll check it out and set it up.
[Modified by lars, 9:03 AM 3/18/2004]
First, oput the carb back to its bone-stock jetting specs. Rich running at idle is usually caused by the throttle blade angles not being set up right. Do the bench setting as outlined in my paper once you have the stock jets back in it: et those primaries and secondaries cracked open to expose .020" of the transition slot on bot pri and sec throttles. Then, turn all 4 mixture screws 1 turn out from lightly seated. Once you get the thing started up, keep the pri and sec idle speed screws adjusted equally and run the float levels to the lower line on the sight glass. Fine-tune the idle mix screws after it's fully warmed up - you may find that it idles best at about 3/4 turn on the screws.
Either way, the stock jetting on a 650 should not run excessively rich if the carb is adjusted right. At most, you may have to change jet sizing by up to 2 sizes. Anything beyond 2 sizes is a possible clue that you have something else that needs to be looked at.
If you can't get it dialed in, send it out to me and I'll check it out and set it up.
[Modified by lars, 9:03 AM 3/18/2004]
