Carb Help needed please!

Make sure all the gas is out of the carb and bring it into the house where it's warm. Cold hands and carburetor work don't go together.

Mike
 
Simple things first.... 1) Is it leaking gas at all?.. when idling ?... when running? or not at all. Is it rich at idle or when running? 2) You Say it's running rich therefore it's most unlikely to be a blocked passageway (other than the air passage at the idle air mix screw which hardly ever gets blocked)..... YET... as you say when you floor it it backfires which certainly could indicate a weak mix
.. so we have ... if running rich .....
A) You didn't by any chance get the GAV seat and the comp jet mixed up and put them in the wrong places?? ( yes...we've all done it !)
B) lack of or poor seal at comp jet gasket can cause rich running withour any visible sign of leakage
C) Assuming solution is not A) or B) then I would suspect either main or comp jet are too large.
if running weak ... suspect crud in passage way or in a jet, or crud preventing good fuel flow from tank.
RonC said "I wouldn't drill out and replace plugs. You run the risk of cracking the casting when forcing in new plugs. Not necessary. Glass bead the passages and run paper clips through the passages to check".... I totally agree with him.
 
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Use a good quality carb cleaner in a spray can with a tube in all of the passages with the jets removed . Replace the original jets and give it another try .
 
I would agree with RonC. Don't fool with the brass plugs. There is a good chance that you will screw up and destroy the carb halfs. Do a complete disassembly and use a common paper clip. you will have to bend the clip in different shapes to get through the 5 passage ways. Use a needle nose pliers to help to push the clip through.(Be patient) then use compressed air to blow them out. Then have the two half's bead blasted and make sure to get into each 4 passage ways. Then redo the the compressed air to the passage ways. Have the 4 jets flow tested. Here are good flow test # Main Jet 158 ML, Cap Jet I73 ML, Comp Jet 143 ML, Idle jet 54 ML. Place a gasket under all except the idle jet. Turn the throttle screw 1 1/2 turns open and the air adjustment also the same and AVR nob (Choke rod) 1/4 turn counterclockwise. two main things to remember clean passage ways and jet flow rates This should get you up and running. Sofield
 
Well I did make some progress today. At least I consider it progress in that when something seem to go right, it feels like progress for me, the guy that does not know what he is doing.

I put my "good" carb(the one I have had on the coupe and it has run great) back on the coupe today. Took the bottom half off the "good" carb and put the bottom half of the carb ("bad" carb) I am trying to get going on the top half of the good carb that was on the coupe. Started up the rig and bingo, the same problems are there that I have had with the bad carb when I put it on the rig. Many of you that know how to rebuild carbs probably knew that this would happen. But old me had to do it on a trial and error effort.

So to me this indicates that the bottom half of the bad carb is messed up somewhere. So now I need to start doing some of the many good ideas you all have suggested in the above comments. I had a can of carb cleaner sitting around so after taking all the jets out of the bottom half, I put it in the can of carb cleaner. Think I will let it soak there for a day or so and then try to clean out passageways with paper clips and then blow them out. Then check over my parts (jets, etc) to make sure they are OK. Then put things back together and give it a try.

Again thanks for all your help and if you don't mind I will let you all know how things work out.
 
Fred, Dave Adair has the carb jet testing setup if you want to flow test your jets. (This might be in the club tool trailer, but Dave will know). Also, I got some of the rcommended Renner's jets and put them in my coupe, but I didn't notice any difference from what I had, which had not been flow tested, but were all original jets.
 
700rpm said:
Fred, Dave Adair has the carb jet testing setup if you want to flow test your jets. (This might be in the club tool trailer, but Dave will know). Also, I got some of the rcommended Renner's jets and put them in my coupe, but I didn't notice any difference from what I had, which had not been flow tested, but were all original jets.
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Thanks Ray. If the stuff I am in the process of doing now, don't work, then I will have to look at your idea with David. I also have a number of jet sets that I can swap out and check out each one.
 
Just a thought, in your original post you said you installed the jet below the GAV, I do not remember, but aren’t the compensator jet and the GAV jet the same thread size?, if so if the 2 are switched it would run to rich , again just a thought.
 
Brian T said:
Just a thought, in your original post you said you installed the jet below the GAV, I do not remember, but aren’t the compensator jet and the GAV jet the same thread size?, if so if the 2 are switched it would run to rich , again just a thought.
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Brian, yes I did check that out and yes I do use the jet below the GAV. From what I understand, the longer of the two jets goes in the GAV. I think I originally put the wrong (the shorter one) in the GAV and somewhere I saw where I should have used the longer one. Is this correct guys? The longer one goes in the GAV??

I am going out this A.M. to see how the soaking of the lower part in carb cleaner did. Then I will try some of the suggestions Tom Endy has in his write up using paper clips to clear the passages. Will hope for solution this time
 
Yes larger port one is GAV seat ...

The comp jet has much smaller port ... and usually shorter
 
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Hey guys, I won! The old carb works!!!. I know it probably isn't as good as one that would have been rebuilt by someone that knew what they were doing, but it works quite well on my old driver 29 coupe.

To fill you in on the last things I did, based on a number of your ideas, that made it work well, I will try to list them off.

1) I soaked the bottom half of the carb in carb cleaner over night.
2) This A.M. I took it out of the cleaner and proceeded to do a number of thing you all had suggested.
3) After washing the cleaner out of the carb, I followed Tom Endy's procedure using paper clips to assure all channels were clean.
4) Then I used air to blow out all of the channels.
5) Then I rechecked what I had done with the fitting down in the GAV channel. I made sure I put in the longer of the two fittings I had.

Then I put everything together with same other parts and put it on the rig and started it up. It seemed to work great so I took it around the block. Still worked great on a little drive. But it did "back off" a bit through the carb when I let up on the gas after giving it a big shot of gas. So may still have a bit of something going on. So I need to get it out on a longer drive under all conditions, to see what it is going to do.

Well better end this chatter and just say thank you all for the ideas on what to do. I think I am getting close to having a fairly good carb. It has been an interesting educational experience for this old guy.
 
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