Re: Serious Carb Flooding Problem

Posted by Steve@Advance on October 12, 2019 at 15:27:46 from (66.169.147.211):

In Reply to: Serious Carb Flooding Problem posted by Mnethercutt on October 12, 2019 at 12:41:41:

Yes, multiple problems...

First, have you check the spark quality at each plug?

Make a spark tester from an old plug with the electrode removed. Connect it at each wire, one at a time, with the base grounded. If you can get it to run long enough all the better, or test it cranking. Should get a consistent, hot, blue spark at the plug end of each wire.

Make sure the points are properly gaped and the distributor shaft has little to no side play.

Back to the fuel system...

The gas running out, as in continuing to flow anytime the fuel valve is open, and black smoke when running, indicates the bowl is overflowing gas. For whatever reason, the needle valve is not closing, or the seat is leaking where it screws into the upper housing.

You have correctly covered most troubleshooting procedures. Look the housing over carefully for cracks or casting pits that may allow fuel to bypass the needle valve completely. Make sure the seat is screwed all the way in and compressing the gasket. Make sure the float is not touching the side of the bowl.

Before assembling the top to the bowl, turn the top upside down. Check the float level with the gasket in place. Best I remember the top should be about 3/16" from the gasket. Give it the "suck test". Suck on the fuel in fitting, hold your tongue over the hole. It should hold vacuum. If it doesn't there is a leak.

How is the tank? If it is flaking rust or contaminated with rust, the same will be in the carb. It only takes a tiny speck of trash to hold the needle valve open. Take a sample in a clean glass, see what you catch.

If necessary take the tank off, rinse it out with E85. If it's flaking rust, just a matter of time it will be leaking. If in the budget, replace it. There should be a screen in the carb inlet fitting, a screen in the separator, and possibly a screen standing above the outlet fitting in the tank. I do not recommend inline filters on gravity systems. If you do want an inline filter, go with the screen type, not pleated paper.

When making the final connection of the fuel line to the carb, open the fuel valve and let gas flow through the line to flush anything still inside. Then make the connection with gas flowing. That will keep any debris from getting in the end of the line or the carb fitting while making the connection.

As for needing partial choke...

If the ignition system passed it's test, then you either have a major vacuum leak, or the main jet is blocked in the carb. Common causes of a blocked main are the tip of the adjusting screw is broken off in the jet, or it is clogged with dried residue. The ethanol residue is known for attaching itself firmly to the ID of the jet. Soaking and blowing won't get it out, it has to be mechanically scraped out with a torch tip cleaner or a small drill bit.

Look at the throttle plate, the fit in the bore. With the stop screw backed off, the plate should seal completely to the bore. If it's not centered, loosen the screws, center it. Be careful, the screws may be Locktighted, they will need heat to release them. Be sure the holes just above the throttle plate are open, be sure the hole in the gasket aligns with the passage in the top and bowl. That is where idle fuel is drawn up.

There are exploded views of the carb online. Look closely to be sure everything is in place, as in the mixing tube, and the ventura is in the right way. There are also adjustment specs procedures, and flow diagrams. The better you understand the theory, the easier to diagnose problems and correct them.

Once it's back together and running reasonably well, it can be adjusted. The carb can only function as well as the rest of the engine performs. If you haven't already done so, open the valve cover, look the valve train over, adjust the valves. Run a compression test, look for differences between the cylinders or one or more cylinders down on compression. Try a spoon full of oil in each cylinder, if the compression dramatically increases, the rings are leaking. However, the rings may just be washed down from the flooding. Also check the oil for gas contamination.

Back to the carb, when you are ready to adjust it, be sure the engine is up to operating temp with a thermostat in place, everything else has been checked, adjusted, and repaired as best as possible, the air cleaner is serviced and connected.

Start with the idle adjustment. The engine must be at very slow idle, 400-500 RPM. Turning the idle mix screw in richens the mix, out leans it. You are adjusting air bleed, not fuel. There is minimal adjustment. If no reaction, the idle is too high or something is still clogged in the carb.

Then adjust the main jet. It's a little different. Start around 2 turns off the seat, being gentle seating it so not to break the tip off the screw. With the engine at slow idle, quickly open the throttle fully, observe the engine reaction. If it takes throttle without hesitation, close the needle 1/4 turn, repeat the test. The object is to lean the mix until the engine stumbles on acceleration, then back the screw out 1/4 turn at a time until the engine will take sudden throttle from idle without hesitation. A single puff of black smoke is the goal.

A lot to digest, but knowledge is power. Keep after it, you can do this. Replacing the carb should be a very last resort, and it won't fix it if there are other problems. The new carbs are generic fit all knock offs, not the same quality as the original.

Let us know how it goes...

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