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Thread: Carb / vacuum question
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11-26-2013, 10:52 PM #1
Screaming And Flying!
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Carb / vacuum question
I need to lean out my midrange.
I really dont have a way to adjust the midrange jetting in these Yamaha carbs. I am thinking about playing with emulsion tube length. Trying to figure out if I should go longer or shorter. I have some longer ones from another carb that look like they would work and I can always cut down the existing to get a shorter tube.
Im not sure where vacuum is higher, at midrange rpm or wide open. I would think at wide open vacuum would drop off.
My guess is that the extensive intake stuffing has created a stronger signal to the carbs at lower RPM's and I need a longer emulsion tube to compensate.Last edited by Mr. Demeanor; 11-26-2013 at 10:56 PM.
13' Biel tunnel AKA "Flight Risk"
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11-26-2013, 10:59 PM #2
Screaming And Flying!
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The existing emulsion tubes are pretty short. Damn...upside down as too!
13' Biel tunnel AKA "Flight Risk"
13" Modified Yamaha V4 - 101 mph
21' Paramount
Mercury 300 Promax
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11-26-2013, 11:29 PM #3
Screaming And Flying!
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Being in front of the throttle plate do those not work on the main jets only at near WOT??
Dave1980 Cougar 19 tunnel,90 2.4L Bridgeport EFI in middle of restoration.
1988 BAJA Sunsport 186, 96 225 Pro Max
79 12' Auminum, 95 Merc 9.9
RIP Stu
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11-26-2013, 11:41 PM #4
Screaming And Flying!
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There are a series of small orifices that feed fuel at idle and then transition to the main jet but its on the main pretty quick. I have watched it pull fuel with just a small blip.
13' Biel tunnel AKA "Flight Risk"
13" Modified Yamaha V4 - 101 mph
21' Paramount
Mercury 300 Promax
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