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[Randtor]

I am in the process of reworking my entire fuel system out of necessity, it sat too long. I have rebuilt the fuel pump, changed hoses, reset the timing the proper way ( I have pertronix ignition, and have also changed to negative ground), using the light on/off method via the distributor. My carbs were running awful, so I pulled them off, took them completely apart and cleaned everything. Soaked the cork seals in oil, and was able to re-use everything. I did not change the needles or remove them thus they are still seated in the pistons exactly as before. The pistons slide freely up/down after the cleaning; I centered the needle as instructed (University motors has a real nice video on youtube) and had a nice 'clunk' when allowing the piston to drop. In essence everything was cleaned and put back together properly.
After adjusting air flow correctly and with the TR running with a 'fluttering' idle around 900rpm, I attempted to set the mixture. Hooboy... I started with the nuts that move the jets (on the bottom of the carbs) turned out 2 1/2 turns (15 flats), as suggested, and I was blowing black smoke out the tailpipe with both carbs (tuning independently as per instructions). After turning the nuts repeatedly (turning them so they moved UP toward the bottom of the carbs), trying to get the mixture to run leaner, I had the nuts turned all the way up, and I was still running very rich.  Black smoke still out the tailpipe, and the smell of gas is pervasive.
So where do I turn? Is this a carb issue, or something else not allowing the carbs to tune properly?
Any suggestions would be appreciated. Thanks, Rand

[TR3driver]

Several possibilities come to mind.  Most obvious, did you make sure that the jets moved up after adjusting the nuts?  Sometimes they stick and the spring doesn't pull them up, you have to give it some help by hand.  Same thing can happen after using the choke (one of mine stuck just last month).

Are you certain the upper jet seal is working?  If it leaks, it allows extra fuel to be sucked in while the engine is running, no external leak is apparent.  My experience was that the cork versions only lasted a few years of daily driving, so I switched to the rubber O-rings from Moss (which last much longer).

Check the floats for fuel inside.  Might also be worth checking the fuel pressure with the engine running.

Bad valve adjustment (or timing) can show up as rich mixture.  So would clogged exhaust (like a collapsed tube inside the muffler) although the stock "glasspack" mufflers rarely fail that way.

Not likely if the car was running good before it's long storage, but another possibility is wear in the jets and needles.  Had that problem with exactly your description on a friend's MGA many years ago; and to a lesser extent on Dad's TR3A.

And of course the most obvious, are you sure the carbs are assembled properly, and the big nut is tightened enough to clamp the jet housing in place?  If it is left loose (due to a swollen cork gasket, perhaps), the internal spring will hold the housing too low and you can't get the jet high enough.

[Randtor]

Randall,
All good suggestions to check, thanks. Jets are centered and the pistons moved smoothly, clicking on the gate when they drop down nicely. Plenty of fuel in the bowls, and I made sure to get the right measurement on the floats on both carbs. Timing was set just prior to cleaning the carbs, it should be pretty close, enough so that I shouldn't be running rich.Muffler is free and clear. Big nut on the bottom is very tight. Which leaves us with a few other of your possibilities...
(a) When I put the carbs back together, I questioned the proper alignment of the dished washers on either end of the jet bearings... are the convex surfaces facing each other, or are the convex surfaces each pointing away from the center of the bearing shaft? 
I frankly did not take note of that when I pulled them apart. I can't remember which way I put them together, so either way I am hgoing to have to take them apart again anyway!
(b) I reused the cork seals which I soaked in oil for a while prior to re-installing. But, one of them was torn. I had no replacements so I put it in anyway. Now, both carbs are about equally running rich, so I don't think this has had much of an effect. But certainly the cork seals are old, and probably need replacing.

So, I'm going to buy a carb rebuild kit! How extensive should the rebuild be? Do I need to replace the throttle shaft bushes, shaft and disc, along with needles, bearings, valves, washers, seals, et al??

As always, thanks for the help!

[charley fitch]

While discussing this problem with another owner, he had these ideas.

Make sure that the top of the jet is flush with the carb body as seen in the throat of the carb.  When you centered the needle did you make sure that the jet was all of the way up and flush with the carb body at the top?  This is before you back the jet off to adjust it.  If the needle gets centered without the jet being all of the way up, it may not be centered at the top of the movement.  This will prevent the needle from going all of the way down. I am guessing that this may not be true as you say the piston clicked against the carb body in the downward movement.  But if you didn't have the jet all of the way up it will cause problems.

The other idea is to adjust/lower the needle down slightly.  This will lower the needle in the jet. The idea is to get the shoulder of the needle to come in contact with the top of the jet prior to adjustments.  If the needle is to high into the piston then it is allowing the fuel to come out of the jet when it is supposed to be closed.

One last item is to be sure to disconnect the linkage to the choke prior to trying to adjust the carbs.  When done connect the choke linkage back up and adjust it so that it does not pull on either jet until you pull the cable. 
Charley Fitch 

[TR3driver]

The little dished washers in the jet bearing go with the convex sides towards the spring/each other.  The concave side faces the seal (to force it towards the jet).

Unless they are badly worn, I would leave the throttle shafts & bushings alone.  They can't cause the mixture to go rich (only lean), and my experience has been that even a badly worn shaft won't cause problems until it lets the throttle plate drag on the bore so badly that it won't close properly (leading to having to 'blip' the throttle to bring the idle down).  They're also kind of expensive and tricky to fit.

But if you don't know their condition, then I would suggest replacing the needles and jets.  I've seen several cars where the jet was so badly worn inside that the idle mixture could not be leaned out, and yet there was no damage visible to the naked eye.

In addition, I would suggest replacing both the choke return spring (Stanpart 108320), and the spring between the gland seals (Stanpart 108315).  Many people (including myself) try to fiddle with those springs (stretch them and/or cut off coils) with the result that the choke never works right again.  The springs are not included in any kit (AFAIK), but are available separately from Moss & TRF (maybe others).

[Randtor]

Well, here's an update: I did a complete rebuild except for shaft bushings. Went well. Put both carbs on, and I was able to adjust the front carb pretty well, but the back carb seemed unresponsive. So, I bought a Uni-Syn and a color tune. Balanced the airflow, and used the color tune. As suspected, the front carb tunes nicely, I get a blue color flame with a little orange tinge at idle. The rear carb just will not balance the same. I pretty much lean it out all the way, and I still get yellow with some orange, indicating it is still running rich! I took out the pistons and lowered the metering needle in both carbs, that helped the front one nicely, but again made no difference in the rear carb. The pistons click nicely on the bridge, so there is no issue with piston sticking; everything is new, and both carbs have been assemble identically. I don't suspect a vacuum leak as the car would likely run too lean if that were the issue; also, I did spray carb cleaner everywhere and never identified a vacuum leak anyway. I disconnected all linkage when tuning, so no issues there as well.

So, I am coming to the conclusion that in fact I have an engine problem, perhaps the rear 2 cylinders?? I don't know what else to think at this point. The rear carb seemed to be the trouble maker before the rebuild, and it continues. Since the timing has been reset, and the front carb is adjustable as expected, would my conclusion make sense? If so, what could be the problem?
Thoughts? Opinions? I am at a loss......
Rand

[TR3driver]

Have you checked the valve clearances?

If so, I would try swapping jets & needles front to back.

Another possibility would be a bad float in the rear carb (assuming you adjusted the float level during the rebuild).

[Randtor]

Latest update. Very weird. The front carb worked well, the rear would not lean out. I had a friend over to take a look. He thought the jet bearing was not seated properly in the carb body, we loosened the bottom nut (as if to center the needle, which I had done a half dozen times already!)and he wiggled and jiggled the damn nut, jet bearing and all. Pushed up and down, pulled to and fro. Put it back together and lo and behold everything worked fine. I dunno. I can't really explain what happened. Maybe it was the Prince of Darkness trying to expand his horizons and pull a fast one on this backyard mechanic :-). In any event, alls well that ends well...  for now! So out goes thr TR3 and in comes the Stag... rear end hypoid leak, pretty nasty. Can't wait to see what's in store for me now!

[TR3driver]

Glad you got it sorted, Rand.  Kind of sounds like maybe the upper washer wasn't sealing, allowing fuel to be drawn around the outside of the jet & upper bearing.

Hopefully the Stag diff will go easier, and you won't find what I found:


As usual, I never did get around to writing an article, but there are some photos at
http://s258.photobucket.com/albums/hh260/TR3driver/Stag%20diff/
that might help.