Marbel carb expert??

Geo-TH,In

Well-known Member
What could be wrong with the lower part of marvel carb that causes a rich mix? You could turn the main jet all the way in or out. Same with idle jet. No change, just a rich burn. So rich you smell like gas just being next to tractor. Plugs would turn black in seconds.

The carb came off a 1963 MF35. I took the lower part of a used Jubilee carb. Simply by installing the Jubilee carb bowl and using the main jet screw, we can now adjust fuel mix and lean tractor down. It runs as it should. Doesn't miss a beat. No more smelling like gas.

So, what could be wrong? There is no apparent damage to main jet or main jet adjusting screw. Any ideas?
a187372.jpg
 
Maybe its just the photo,but it appears that the flange that supports the venturi is mostly gone, which could allow the venturi to sit crooked and not create the proper vacuum in the right place. That could be built up with solder, brass, or epoxy and bored into shape, or just solder the venturi into place.
 
If the main jet it self has been drilled out larger or other wise damaged that will cause that. Or if the brass tune that sits at an angle has had the holes reamed out or the jet at the bottom of the tube has been drilled out that too can cause that problem
 
(quoted from post at 15:48:26 03/25/15) What could be wrong with the lower part of marvel carb that causes a rich mix? You could turn the main jet all the way in or out. Same with idle jet. No change, just a rich burn. So rich you smell like gas just being next to tractor. Plugs would turn black in seconds.

The carb came off a 1963 MF35. I took the lower part of a used Jubilee carb. Simply by installing the Jubilee carb bowl and using the main jet screw, we can now adjust fuel mix and lean tractor down. It runs as it should. Doesn't miss a beat. No more smelling like gas.

So, what could be wrong? There is no apparent damage to main jet or main jet adjusting screw. Any ideas?
a187372.jpg
eorge, experts are few & far between, but OboElitist looks like your winning ticket here. No guesses on his part, just simple observation...I like.
 
A semi-educated guess anyway. It could have a blockage or corrosion hole inside the galleys somewhere too. Check them wiTh wire and carb cleaner
 
Why is this thread continuing? Unless that initial photo it horribly deceiving, the seat for the venturi tube (recessed ledge in the bowl, marked in the yellow in my photo below) is simply missing. Perhaps corroded away or by whatever means absent & without it, no way to seal the lower end of venturi tube to bowl, which is necessary for carb to function correctly.
 
"Why is this thread continuing?"

Because Gary hasn't chimed in? ;)
I can't say I've seen one with the seat gone that badly.
See something new every day.
Now I wonder what caused it to disappear.
 
(quoted from post at 19:44:09 03/27/15) "Why is this thread continuing?"

Because Gary hasn't chimed in? ;)
I can't say I've seen one with the seat gone that badly.
See something new every day.
Now I wonder what caused it to disappear.

Looks like a casting defect to me. Should have been scrapped before it left the Marvel-Schebler factory, but instead, someone figured out a way to make it work.
 
(quoted from post at 09:37:12 03/28/15)
(quoted from post at 19:44:09 03/27/15) "Why is this thread continuing?"

Because Gary hasn't chimed in? ;)
I can't say I've seen one with the seat gone that badly.
See something new every day.
Now I wonder what caused it to disappear.

Looks like a casting defect to me. Should have been scrapped before it left the Marvel-Schebler factory, but instead, someone figured out a way to make it work.
o ya rekon that's why they called it a "Marbel"? :roll:
 
(quoted from post at 07:13:30 03/28/15)
(quoted from post at 09:37:12 03/28/15)
(quoted from post at 19:44:09 03/27/15) "Why is this thread continuing?"

Because Gary hasn't chimed in? ;)
I can't say I've seen one with the seat gone that badly.
See something new every day.
Now I wonder what caused it to disappear.

Looks like a casting defect to me. Should have been scrapped before it left the Marvel-Schebler factory, but instead, someone figured out a way to make it work.
o ya rekon that's why they called it a "Marbel"? :roll:

:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:
 

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