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YH carb assistance
Posted by: corvairsince70 ()
Date: January 13, 2021 01:35PM

I am having trouble with my stock '66 YH carb on a stock 180 engine. I know what is happening, just not why.
When I open the throttle just "off idle", excess gas pours out of the pump discharge nozzle. This floods and bogs the engine. Also drips very slightly at idle. Over 30 mph the engine runs good.

1) I rebuilt the carb and check every part and passage using Bob Helt's book.
2) Float level is at 3 / 4". Took off carb top and gas is about 1 1 / 4 from the top of the bowl.
3) Float is good, no leaks.
4) Ran engine without fuel pump to check for excess fuel pressure. Just ran with gas in the carb, no difference. Still flooded at off idle.
5) Made sure pump discharge needle was present.
6) Double checked accelerator pump. New, soft, and no tears.
7) Jet and metering rod are stock and correct numbers for this carb. Rod is set flush to 1 / 32 below top gasket surface.
8) This is not a hot soak problem since engine and carb are not hot. Just around the block to get engine warmed to set idle speed and mixture. Choke full open. Idles 830, mixture screw just over 3 / 4 turn from seat.

What am I missing?

Dennis
Nashville area

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Re: YH carb assistance
Posted by: joelsplace ()
Date: January 13, 2021 03:10PM

Did you sand flat the top cover of the accelerator pump? They are often warped.
It is also possible your air filter is not flowing enough air. Third thing is the choke. Is it open for sure?
Did you set the rod height?

Joel
Northlake, TX
5 Ultravans, 114 Corvairs and counting...

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Re: YH carb assistance
Posted by: Brizo ()
Date: January 13, 2021 07:54PM

Corvairsince70, Your description sounds like the pump / metering rod is raising too soon when the throttle is opened. This is often because the vacuum below the diaphragm is weak and barely able to hold down at idle as it is. If the throttle body flange on the bowl is warped the vacuum may be leaking away where it passes through the thick gasket. For a test, remove the carb, remove the top, push the pump down, open the throttle and place a finger over the vacuum hole in the throttle bore. Then release the pump - it should stay down for at least a few seconds. Also, late ignition timing on a turbo will cause low vacuum and contribute to the problem.

Dan Brizendine, Circle City Corvairs
'64 8 door Greenbrier, +.060 stroked 186 ci.140 PG. "In beautiful Wanamaker Indiana...with one stop light and 5 pizza shops"

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Re: YH carb assistance
Posted by: jjohnsonjo ()
Date: January 14, 2021 06:01AM

Never tried it that way, but I use my hand vacuum pump. With the carb off and a small nozzle to pump a vacuum into that circuit port hole and see how it works and how well it holds a vacuum.

Also, add a full size vacuum gauge to the boost retard line and see what the idle vacuum is. If you have a ruptured diaphragm the vacuum will be too low for the car to work correctly.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
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2016 KIA Sorento SXL Turbo

Bethlehem,Pa





Edited 1 time(s). Last edit at 01/14/2021 06:03AM by jjohnsonjo.

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Re: YH carb assistance
Posted by: corvairsince70 ()
Date: January 14, 2021 01:25PM

Thanks Dan.
It was the thick throttle body gasket that was not getting a good seal to the carb. This caused a vacuum leak so the accelerator pump would not stay down. No more flooding.
Thanks again.

Dennis
Nashville area

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Re: YH carb assistance
Posted by: MattNall ()
Date: January 14, 2021 01:29PM

Great!

MODERATOR
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..............................110-PG.................................................Webered-Turbo

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