Rpms go up when choke is pulled.

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jsfarmall
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Rpms go up when choke is pulled.

Postby jsfarmall » Sat Jan 27, 2018 9:47 am

No matter the throttle setting, when I pull the choke the rpms go up. It's not a small amount either. I have gone around the joint between carb and manifold with carb cleaner and starter fluid both and no change in the engine. Done the same where the manifold connects to the engine. Engine fires right up easily, does have a slight sputter at times though. Anyone got advice or experience with this issue?

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Re: Rpms go up when choke is pulled.

Postby staninlowerAL » Sat Jan 27, 2018 10:13 am

I've got a ATV that does this when the choke is part closed. Idles back to normal when the choke is off. IMHO it is the change in the fuel/air ratio that is causing the faster idle rpm.

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Re: Rpms go up when choke is pulled.

Postby inairam » Sat Jan 27, 2018 10:41 am

Do you need to pull the choke partially for the Cub to run?
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jsfarmall
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Re: Rpms go up when choke is pulled.

Postby jsfarmall » Sat Jan 27, 2018 11:11 am

Only when the engine isnt warmed up yet. After it warms up it will run without it. It runs slightly smoother when choke is partially pulled though. I even cleaned the carburetor out, which wasn't bad at all, just be sure that's wasn't it.

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Re: Rpms go up when choke is pulled.

Postby Eugene » Sat Jan 27, 2018 11:39 am

jsfarmall wrote:Only when the engine isnt warmed up yet. After it warms up it will run without it. It runs slightly smoother when choke is partially pulled though. I even cleaned the carburetor out, which wasn't bad at all, just be sure that's wasn't it.
Check or recheck the float/fuel level and float drop in the carburetor.

I think the fuel level in the carbuetor is a bit low.
I have an excuse. CRS.

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Re: Rpms go up when choke is pulled.

Postby MiCarl » Sat Jan 27, 2018 1:38 pm

ATVs typically don't have a choke. They've got an enricment circuit which is typically labeled "Choke" as it accomplishes the same thing - easier cold start. These do also boost the idle speed unless it gets warm enough to slow down from being too rich.

The Cub has an honest choke. If it's boosting the RPM on a warm engine the fuel mixture is too lean. If you don't have external air leaks then you've got a low float, clogged jets or mis-adjusted.
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Re: Rpms go up when choke is pulled.

Postby Lt.Mike » Sun Jan 28, 2018 7:48 pm

Possible vacuum leak also. Perhaps the bowl gasket is sucking air.
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