wont run right

1948jr · Aug 30, 2018

what causes a carb to hesitate when u throw the coals to it?

grizz02 · Aug 30, 2018

what causes the engine to stumble when you go to WOT is a lean condition such as a main jet pluged or the ignition timing not advancing or can be intake leaks

old · Aug 30, 2018

If on a tractor then it is common. A carb on a tractor does not have an accelerator pump like the old car carbs have so when you open it up fast it takes a moment or to, to catch up. That is why the tractor throttle is to be set at a speed then used not to accelerate on the go like you do a car

wilson ind · Aug 30, 2018

maybe should use fuel required instead of coal!! could not resists

Steve@Advance · Aug 30, 2018

Check the ignition system, be sure the plugs are fresh, change them if any doubt. Be sure the wires, cap and rotor are good.

Check the distributor shaft for side play, check the point gap, check the centrifugal advance, and the timing.

Assuming we're talking about a tractor, with an updraft...

Once everything is right, then go for the carb. Be sure there is sufficient fuel flow to the bowl. Get the engine up to operating temperature. Adjust the idle mix for best idle, then ever so slightly rich. Open the main jet adjustment about 1/8 turn at a time, give it sudden throttle from idle after each adjustment. When it's right, it will take throttle without hesitation. A single puff of black exhaust is desirable.

If there is no main adjustment, the carb will need to come apart and be cleaned. Pay particular attention to the main jet, scrape it out with a small wire, but don't enlarge it. Be sure the float level is to spec.

grizz02 · Aug 30, 2018

that's just wrong LOL

casecollectorsc · Aug 30, 2018

Don't think they need a accelerator pump as I just got a 88 and 83 year old tractors running this summer...one sat since 58. You grab the throttle linkage and pop it wide open and they both jump to attention.....

showcrop · Aug 30, 2018

Just a little clarification of Steve's post. The idle mixture is set with the AIR screw which is usually up near the top of an updraft carburetor. To richen your idle, so that it will "pick up" a little better you turn the air screw IN.

VicS · Aug 30, 2018

Yes a little lean. But a 40000 volt coil and electronic ign will really help.

MarkB_MI · Aug 30, 2018

Most carburetors go lean when the throttle is advanced, because there's a lag between when the throttle is opened and when increased airflow through the venturi starts sucking more fuel. Most automotive carbs have an accelerator pump to compensate. Some had "power valves" as well. Motorcycles and some sports cars use "constant velocity" carburetors, where the airflow through the carb is restricted to prevent the mixture from going lean.

Tractor engines aren't expected to respond instantly when the throttle is opened, so they don't typically have accelerator pumps or power valves, nor do they need CV carburetors.

RandyB(MI) · Aug 30, 2018

depends on what tractor and what carb. Even a 2cyl JD will not hesitate when carb and all is right. Could narrow it down more if I knew what it was.

Leroy · Aug 30, 2018

First off we need to know what make and model of tractor we are talking about. What you are talking about tractors not having acelerator pumps is not correct for all. Some do like the Ford from 1965 and up. My 68 had the pump so froze up in the bore the garage could not get it out and had to send the carb out to get it done. Was a garage that used to be Ford tractor dealer. The curent at the time Ford tractor dealer never even realized it had an acelerater pump with the tractor in their shop could not get it to run correctly or keep on running.

wont run right

1948jr

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grizz02

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old

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wilson ind

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Steve@Advance

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grizz02

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casecollectorsc

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showcrop

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VicS

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MarkB_MI

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RandyB(MI)

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Leroy

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