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DSeries4 
Orange Level
Joined: 12 Sep 2009
Location: Ontario, Canada
Points: 7445
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 Topic: CA Idle
Posted: 30 Nov 2024 at 7:22am |
First off: Happy thanksgiving to all of my friends in the USA!
With that out of the way, let's talk about my little CA. Love it and runs like a swiss watch, but I can't get a good low idle out of it. Low idle seems very fast - maybe between 8-900 rpm (with no tach of course). Bringing the throttle lever lower basically shuts the engine off - no decrease in engine speed, no coughing or sputtering.
Throttle response is good and high idle seems to be where it should be. Carb was rebuilt a few years ago and playing with the low idle screw does not make a difference. The throttle lever going to the governor does have some wear and slop and I was thinking that might be the cause of its problem, but I am not really sure. Still 6 volts on points with positive ground and usually starts on the first try.
Any thoughts?
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'49 G, '54 WD45, '55 CA, '56 WD45D, '57 WD45, '58 D14, '59 D14, '60 D14, '61 D15D, '66 D15II, '66 D21II, '67 D17IV, '67 D17IVD, '67 190XTD, '73 620, '76 185, '77 175, '84 8030, '85 6080
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DrAllis
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Joined: 12 Sep 2009
Points: 21408
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Posted: 30 Nov 2024 at 7:31am |
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Two things. #1. If the throttle shaft itself is loose in the carburetor body, you are sucking air thru that area and they cannot idle correctly. #2. Is the idle speed screw able to hit the roll pin stop that should be sticking out of the carb body ?? I just noticed my new to me D-10 is missing the roll pin, therefore when you try and idle down just a wee bit too much the engine just quits because the idle speed screw is ineffective with no stop to hit.
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DSeries4
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Joined: 12 Sep 2009
Location: Ontario, Canada
Points: 7445
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Posted: 30 Nov 2024 at 7:38am |
The carb was rebuilt with new pins and bushings, so I don't think it's sucking air. The engine runs very smoothly through out the speed range. I have not looked close enough recently for the low idle roll pin. I will take a look this afternoon and report back on my findings. Many thanks Doc!
I forgot to mention it is the Zenith carb.
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'49 G, '54 WD45, '55 CA, '56 WD45D, '57 WD45, '58 D14, '59 D14, '60 D14, '61 D15D, '66 D15II, '66 D21II, '67 D17IV, '67 D17IVD, '67 190XTD, '73 620, '76 185, '77 175, '84 8030, '85 6080
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DrAllis
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Joined: 12 Sep 2009
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Posted: 30 Nov 2024 at 8:01am |
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Mine is a Zenith too. Those carbs used a roll pin stop where many Marvel carbs had a cast ear sticking out for a stop.
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tbran
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Joined: 14 Sep 2009
Location: Paris Tn
Points: 3482
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Posted: 30 Nov 2024 at 9:17am |
At 800-900 the engine is flowing enough air that it is going from the idle circuit to the main jet system. As Doc stated either you have an air leak or the jet/passages of the idle circuit are plugged. When the idle screw is turned all the way in the increased air flow should flood the engine. But, as stated you are running off the main jet.
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When told "it's not the money,it's the principle", remember, it's always the money..
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DaveKamp
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Joined: 12 Apr 2010
Location: LeClaire, Ia
Points: 5971
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Posted: 30 Nov 2024 at 9:19am |
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Too much timing advance will do this, too... A manifold leak could, but the mixture would be lean, whereas a carbeurator shaft leak would usually not...
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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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AC720Man
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Joined: 10 Oct 2016
Location: Shenandoah, Va
Points: 5139
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Posted: 30 Nov 2024 at 11:33am |
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Tbran that’s a great source of information. Really good explanation of how it all works. I’m going to research that site for my D14 carb.
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1968 B-208, 1976 720 (2 of them)Danco brush hog, single bottom plow,52" snow thrower, belly mower,rear tine tiller, rear blade, front blade, 57"sickle bar,1983 917 hydro, 1968 7hp sno-bee, 1968 190XTD
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jvin248
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Joined: 17 Jan 2022
Location: Detroit
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Posted: 30 Nov 2024 at 6:02pm |
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Old car vacuum leak check was spraying with carb cleaner and listen to engine rpm change. Might work on your carb to check for air leaks.
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captaindana
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Joined: 14 Sep 2009
Location: Fort Plain, NY
Points: 2545
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Posted: 01 Dec 2024 at 5:03am |
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My D19’s roll pin was missing and acted exactly as that.
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Blue Skies and Tail Winds
Dana
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