carberator question

RobLavin

New User
Hello.

I have a Harry Ferguson TO30. I had the carb rebuilt after setting for a couple of years (gum deposits from the gasoline). I now have it back in the tractor, but I have to choke it a little to keep it idling. When I tried to mow a field with it, I also noticed that I had to gradually adjust the choke open even more to keep the tractor from sputtering. In looking at it afterwards, I noticed that the large adjustment screw on top of the carb doesn't turn in a circle. It turns in more of an ellipsis (like the screw inside might be bent), and only turns about 3/4 of the way around before it hard stops. Is this normal? I haven't tried to adjust it before.

I am wondering if I should

A- take this carb apart, fix the large adjusting screw and reassemble,

B- replace this carb with a new Marvel Schebler or

C- replace this carb with a Zenith (which I found online saying that it was a better performing carb than the original). This is still a 6 volt system, and not used too often.

Thank you for any information!
 
(quoted from post at 18:24:35 09/02/15) Hello.

I have a Harry Ferguson TO30. I had the carb rebuilt after setting for a couple of years (gum deposits from the gasoline). I now have it back in the tractor, but I have to choke it a little to keep it idling. When I tried to mow a field with it, I also noticed that I had to gradually adjust the choke open even more to keep the tractor from sputtering. In looking at it afterwards, I noticed that the large adjustment screw on top of the carb doesn't turn in a circle. It turns in more of an ellipsis (like the screw inside might be bent), and only turns about 3/4 of the way around before it hard stops. Is this normal? I haven't tried to adjust it before.

I am wondering if I should

A- take this carb apart, fix the large adjusting screw and reassemble,

B- replace this carb with a new Marvel Schebler or

C- replace this carb with a Zenith (which I found online saying that it was a better performing carb than the original). This is still a 6 volt system, and not used too often.

Thank you for any information!

The main jet adjustment should turn freely. You should be able to turn it in until it stops and turn it out until it comes out of the carb. The original Marvel Schebler is a fine carb. I would just get a new main adjustment screw. You might find one for a Ford N series easier to find. Their part number is 9N9565C
 
Jason-

Thank you for the quick, informative reply.

One last question - should I then just put some pliers on it and wrench out the old screw (counter clockwise I assume), or take the carb apart and try to cut off the bottom if it, or something else?
 
Large adjustment screw on top needs to be set at about 1 1/4 turns to start then fine tune it. The
small(air) adjustment needs to be set about 1/4 or 1/2 turn. This will get you started. The screw seems
to be bent from what your telling. After setting it should throttle up OK, if not then you can set more
or less if it needs it.
 
Thank you for those settings, that will help. Is it safe to just take some pliers to it to get the old screw out, or is there a better way? I don't want to strip the threads or something. If I turn it counter clockwise, it turns about 3/4 of 1 turn and then stops, so I would need to wrench on it to unscrew it.
 

I would take the carb apart because they may have put the carb halves together with the needle in it which is a no no! It's possible that they missed the main jet when putting it together. Besides if you have to choke it to keep it running...you may want to clean the carb while you have it apart because it sounds like it is still stopped up,or the fuel delivery up stream of the carb is stopped up.
 
The screw mentioned has to come out. I would take the carb apart first, look at it inside, and decide how to proceed. If the screw
is bent, you will need another. I doubt you can straighten it satisfactorily although of course you can try. The main jet requires
a deep well 3/8 slim socket to remove and replace it. As mentioned, that is possibly the fuel 'searching' problem.
 
Try cleaning the air filter first . A clogged or restricted air flow will make the engine want more fuel to keep going especially at low rpm . The metal mesh inside the canister can be taken out and washed . It is surprising just how much rubbish takes up residence inside it .
 
Sounds like the carb probably got dropped and bent the main adjust screw. It should screw out, but there is a
chance it might break off. I think I have one, need to see if I can find it.

Having to choke it means it's too lean. Be sure there aren't any vacuum leaks, won't work if there are any
leaks.

Also the idle mix adjusting screw adjusts backward than most. Screwing it in richens the mix, out leans it.
If it needs choke to idle, turn the mix screw in a little.
 
(quoted from post at 11:51:33 09/02/15) Large adjustment screw on top needs to be set at about 1 1/4 turns to start then fine tune it. The
small(air) adjustment needs to be set about 1/4 or 1/2 turn. This will get you started.

I saved some adjustment setting from a past post and it stated 1 1/2 for large and 2 1/2 for small then get engine warm and at full throttle adjust the large until engine bogs then back out till smooth and at idle to do the same with the small in till bogs then back out till smooth. you seem to have a much smaller turn on the small Just curious as mine has started backfiring when turned off..
and want to get it adjusted as best as possible
 

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