carb question

Charlie M

Well-known Member
I have a Zenith carburator off a Farmall 100 that has defied everything I have tried to make it work. Tractor will only run about 3/4 choke. I know its the carb as I have swapped it with one off my A and when put on the A id doesn't run correctly there either. I've had a part several times, soaked in acetone, run small wire through the passages, sprayed, inspected, blown out with air, nothing helps. One area concerns me - it can be seen in the middle of the carb throat as a brass circle, looks like it ties into the idle screw and best I can tell there are some very small holes in it. Can't tell how many and if there are some plugged up. I can get some liquid through it. There aren't any small passages anywhere else that I haven't been able to get out, clean and inspect. Any thoughts before I give up.
 
I've had that same thing happen when there was some junk in the sediment bowl assembly which slowed down the gas flow. I would make sure your gas flow will fill a pint jar in less then 3 minutes and 2 would be even better. Check at the carb drain plug and if slow there check it at the line
 
I put the carb from my A on the tractor and it ran fine so that is how I ruled out anything wrong with the rest of the fuel system. Its definitely something in the carb.
 
you have some restriction in the idle passages somewhere and could be the gasket. I use small drill bits and have a small chuck then by turning by hand have found dirt there when I pulled the bit out find stuff on the end of the bit. Just because you blow air thru doesent mean that passage is fully clean. Customer brought me a carb from his B same symptoms as you have. After using the bits did find dirt an when finished carb ran like new.
 
Have you used a piece of wire or as I do a torch tip cleaner tool and poked out all the passageways?? I have also found at times if one takes a problem carb and takes it apart and then sets it in an oven and bakes it at say 150-200 that drys things out so junk will then move out when you spray the carb out with carb cleaner spray
 
the carb should be soaked in actual carb cleaner for a few hrs. this stuff eats carbon. the rinsed in cool water then blow out all passages.
you can actually see the moisture fly out and see if they are free.
 

There are several variations of that Zenith carburetor, and even more variations in the rebuild kits available aftermarket. The kits are supposed to be more or less universal, but they are not. If I remember right, the main gasket in those universal kits is NOT correct for some models, but that is what you get anyhow. That carburetor that is giving trouble MIGHT just have the wrong gasket. It fits just fine, but does not have all of the holes in the correct places.
 
That thought about the gasket has crossed my mind. I didn't think to look at the old one that got destroyed before it was too late. I took the carb off the BN I just bought thinking it would be a good
comparison to what the problem one should be but it has some differences so that didn't work. I've seen 3 variations of those carbs on 4 of the tractors I have them on.
 
Used to be a product called Hydro-seal. It was the best
carb cleaner ever. You could soak a carb in that stuff,
& it would come out clean in all passages.

Used to have trouble with the intermediate plate on Holley
2-barrel carbs getting plugged on 304 & 345 pickup &
travelall engines. Hydro-seal would clean everything to
new condition.

Wish I could find a bucket yet.
Jim
 
You still have a passage plugged closed . And sofar what you have tried will NOT get the job done . like said below the OLD HYDRO SEAl was ok but there was way better stuff like the stuff i use , this stuff will remove five layers of hide if you get it on you before you can wash it off . And even with this stuff i still run the small drill bits thru the holes after they have come out of the tank and gone thru two hot soapy water washes and two rinses and a blowing out then comes the jet drills and reams and blowen out again . Acetone will do NOTHING . You need a full set of number drill bits and a full set of torch tip drill bits and a pin vise ,Then you just might have what ya need to work on your carb .
 
I am usen something that the EPA would have nightmares over and has been off the market for 40 plus years . I stumbled onto and old parts ware house that had five gallon pales of it setting for years . It is the OLD Berryman stuff we used in the dealerships 50 years ago . I could take the nastiest Holley Four BBl off a big ford gas burner truck take it apart and hook a wire to the bigger pieces and parts and just lower it to the bottom of the bucket and slowly pull it back up and everything was shinny and new looking , Ya did not want to get it on your skin or shoes , shoes or boots were toast by the next morning and skin was badly burnt in a matter of seconds. Ya want it to work fast just keep it warm around 150-180 degrees . Ya don't even think about usen it in the basement . Even the old 40x72 shop would reek for a week after ya did a carb.
 
I still have a very old gallon can of the old Berry mans that I have filtered a few times and it still work very well. I have tried some of the new Berry mans but it is crap
 
Charlie - Sounds like the same problem I had with my 574 some years ago - I had the plastic venturi in upside down, I must have had that carb off a dozen times doing what you're doing now.
 
(quoted from post at 19:06:51 12/26/19) I am usen something that the EPA would have nightmares over and has been off the market for 40 plus years . I stumbled onto and old parts ware house that had five gallon pales of it setting for years . It is the OLD Berryman stuff we used in the dealerships 50 years ago . I could take the nastiest Holley Four BBl off a big ford gas burner truck take it apart and hook a wire to the bigger pieces and parts and just lower it to the bottom of the bucket and slowly pull it back up and everything was shinny and new looking , Ya did not want to get it on your skin or shoes , shoes or boots were toast by the next morning and skin was badly burnt in a matter of seconds. Ya want it to work fast just keep it warm around 150-180 degrees . Ya don't even think about usen it in the basement . Even the old 40x72 shop would reek for a week after ya did a carb.

I used to get the "GUNK" brand carb cleaner from NAPA. THAT stuff would also remove hide. Not anymore.
 

Another trick I learned for cleaning carburetors. Take the carb apart as much as possible. Place the parts, but maybe not the float, into a pot of water, add some detergent, and then put the pot on a hotplate and boil it for awhile. The crud will not completely go away, but it will be loosened up and dried enough that it can be scraped off, or brushed off, and you can finish up with a can of aerosol carb cleaner.
 
Even back when they had a couple different grades of that JOY JUICE . The stuff ya got in the gallon can was ok then they had the stuff in a two and a half gallon can with the full dipping basket that was better and then ya hqad the commercial grade in the fivor i should say the 6 and a 1/2 gallon bucket with the big basket with five gallon of stuff , that is the STUFF i am talking about , this stuff will lift five layers of OLD paint and grud in just seconds not hours , Dip in and lift out .
 
The stuff I have will take off paint very quickly but it is also at least 2 decades old if not older. I did have a 2.5 gal can of it but the bottom rusted out and I lost most of it
 

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