Engine flooding, running rich, black smoke

[RecklessKelly]

A few weeks ago I went to take a drive in my T and it was running excessively rich from the start, it was barely driveable. I suspected the carb so I ultrasonic cleaned the carb and parts, replaced the needle/seat and float with new, new gaskets, set the float height. I saw some bubbles when I put the old float in hot water and thought that may have been the cause. The needle looked fine. The mixture needle is nice and sharp and everything looks fine in the carb. Appears up to snuff according to the service manual. After getting it all together and starting the engine, it still ran the same, puffing black smoke from the pipe and pumping fuel out of the plugs threads. Number one had a puddle of gas around the plug. I had the mixture needle set out one turn, I tried turning it in with no improvement. There are no signs of bowl leaking, I let the car sit for 5 minutes with the tap on before starting and no leaking was found. I am using the hot air inlet tube. The plugs are new and I spark tested them with the hand crank, all four give a nice big blue spark. The old plugs sparked just fine but werent the correct plugs. Either way it runs excessively rich. Any ideas why it would run so rich? Up until then, the carb was not problematic and untouched. The car had sat for a few weeks while I replaced some leaky transmission and pan, valve cover gaskets.

[Drobnock]

Check float level. Check float for leak, float may be lower that spec.

[speedytinc]

Are you sure your mixture needle is bottoming in the jet or feeling like it is when the needle is actually binding in the jam nut?
Rule that out by loosening the nut, keeping the needle in its current position. Then turn the needle into the seat.
I have also seen this rich condition from a jett that loosened or was left out.
I would assume that's not your problem since you were in the carb.

[RecklessKelly]

I tested the new float in hot water before installing. I bottomed out the needle into its seat lightly with the brass nut only turned in two threads. I turned the needle out one turn and ran the brass nut in until it was lightly in all the way. Assembled carb and checked again for one turn out. I could try again.

[Jerry VanOoteghem]

One turn open can be a liittle rich, but not what you're seeing. Is the choke return spring in good condition? As others have mentioned, is your float level set correct?

[RecklessKelly]

The one turn is the mid spec from the book. The choke return spring is strong. I checked that the butterfly was open. I set the float at.25 from the machined carb surface. The original was set ok.

[RajoRacer]

You didn't happen to mix up the center drain plug with that of a Vaporizer - that could cause the too rich problem. Although identical in looks - the NH has a hole drilled in the center - the Vaporizer does not.

[RecklessKelly]

I dont have a vaporizer carb to mix up- unless someone else did. No other parts changed except for the identical float and needle/seat. New checked against the old to make sure they were identical. The drain plug is fine, I recut the taper on a lathe to get rid of the step, it wasnt sealing before.

[Ed Fuller]

Did you recut the taper of the spray needle? If you did, did you remove a lot of material?

Years ago I built up a carb from parts than ran really rich. Turned out the spray needle wasn’t bottomed all the way before I backed it out a turn.

[Corey Walker]

You mentioned at first you suspected a leaky float but have since corrected that problem. If it is set correctly with a new float and it doesn’t drip after sitting then that all should be ok. When you put the carburetor back together is there any chance that you forgot the gasket under the spray nozzle? That will make it run rich and impossible to adjust because gas leaks through those threads. It may even run with the spray needle bottomed out. Just a thought, I’ve forgotten those on occasion but figured it out on the test run.

[RecklessKelly]

I didnt recut the spray needle, it was perfect, I recut the float drain needle. I was going to buy a drain assy but cheapness made me remove it from the cart. I did put the jet gasket in.
I pulled the adjuster rod out and managed to get the needle to turn in at least one more turn in by running the nut down more. I was being carefull not to run the nut down too much and crack the carb body like I read about. I might have had it out a few turns but now with the nut lower, the needle goes in more. I set it at a half turn and will work from there. Its dark now so I will wait to fire it up tomorrow.

[speedytinc]

I see you have a 26. If you replaced the nut and/or needle assembly you can have issues with the needle friction arms hitting the nut before the needle bottoms out. The nut doesnt go in deep enough & the arms are to long. Repop parts! Look closely.

[Fozz71]

I would quit messing around with it and buy a new carburetor and just swap it out and see if it fixes the problem. Pricey but may provide sanity.

[RecklessKelly]

I didnt replace the nut or needle, but the arms were holding back the needle, giving a false sense of the needle bottoming into the spray nozzle. As it stands now, The arms are touching the nut. The nut is showing two threads visible before being fully into the carb body. The needle has two threads visible at 1/2 turn out. The nut was starting to turn tight into the body, I think its down all the way. If I have an issue, I could shorten the arms.

[RecklessKelly]

I got the nut to go in more so I ended up with at least one more turn in of the spray needle. I marked up the needle tip and ran it down all of the way to see witness of it closing. Does this look good for a bottomed needle? The picture shows that the first half of the needle bottoms out in the spray nozzle seat.

[speedytinc]

Does it run with the needle closed? Is there an adjustable range where you can get the idle to stumble when closed & @ a point when unscrewed several turns?

[RecklessKelly]

It runs nice and smooth now, not blowing black smoke as far as I can see in the dark. It idles smooth with the needle 3/4 turn out. If I turn it in any more, it starts to die out. A big improvement over when I first got it. My throttle rod is a little short, I cant get the throttle to close all of the way with the lever so I leaned it out to drop the speed. I tried a bunch of times bending the rod to get it perfect but it needs some bend in it to clear the block center hole, which it was rubbing on for years. I have a rod on backorder. I'll wait till tomorrow to take a run in it before dark. Its all dark backroads where I live.

[RecklessKelly]

I took the car out last night for a good ride, it ran great. Spray needle turned out 7/8 seems perfect. Exhaust is clear.