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Overhauling my mother's 544 AGAIN. This time we're at .060 over. I've never done anything with the carburetor, but it seems like it's time. Has anyone ever drilled the high speed jet in the carburetor to compensate for the larger bore? If so, how big did they make it?

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I can probably start a couple of fires here. But here goes. If you need more gas you probably need more air also. You do not say is it hydro or gear. If gear you could check specs between the two and get an idea there. Personaly I would install a set of good repair sleeves. Go back to standard and expect the overhaul to last twice as long and not have to buy the extra fuel. If hydro that engine was pushed hard as it could stand from the factory. If power is your aim and its gear useing hydro carb distributor and governor settings will make it snappy and hungry. Sorry I did not give you any specs as I do not have manuals anymore. If someone else don't jump in. You should be able to find the manual on line.

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Unless I made a math mistake, a .060" oversize bore increases the cubic inches of the engine by 7.4453 cubic inches.  That's only 1.86 cubic inches to each cylinder.  The carb only feeds fuel to the cylinder that is on the intake stroke, and on a four cylinder, that is only one cylinder at a time. You don't think the carb screw will back out enough to fuel an extra 1.86 cubes?  I bet it will.  I wouldn't worry about it. 

How many times has the engine been rebuilt now?  When was the last overhaul?  Why is it in need again?  How many hours are you getting out of an overhaul? 

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Well I know I assume to much. But it has  a mixture screw? We haven't established what carb it has yet. Even so I'm sure it has a fuel solenoid in that jet. The original solenoid had an adjustable stop screw. Replacements did not. Proper adjust ment was wide open

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4 minutes ago, snoshoe said:

Well I know I assume to much. But it has  a mixture screw? We haven't established what carb it has yet. Even so I'm sure it has a fuel solenoid in that jet. The original solenoid had an adjustable stop screw. Replacements did not. Proper adjust ment was wide open

Either way, I'd wait until it was running and decide from there before doing anything. 

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When I purchased a non running 544 gas gear drive last spring, a former IH and JD mechanic who still has a small shop said he had a guy in Ohio that rebuilt carbs.  I believe it was Denny’s Carb Shop that he sent it to.  With a rebuilt carb, precision spark coil, new plugs, electronic ignition, and having the head cleaned/valves, the tractor came to life.  Someone previously put sleeves/pistons in it and I didn’t touch bottom end.

I would recommend calling Denny’s and see what they say.

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Thanks for the advice. The tractor is a gear drive with a replacement shut off solenoid, no adj screw on this Marvel TSX 683 carb. I have messed with farmall cub carbs that ran lean by using a very small file opened up the jet to richen them up and make them run better. This 544 was running lean and had 2 burnt valves but also had a very sloppy throttle shaft which I replaced and I know will help. Did hydro tractors use a different solenoid with a bigger jet? 

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I would fix the throttle shaft with new bushings. One big issue I have with “c “ carburetor, 

I would not drill out the jet , the mfg. design is fine something else is wrong . 

Do vacuum test to see where your at ? 

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The solenoid is the same between gear and hydro. It comes without jet. The jets are probably different but I don't know that for a fact. Again the manual. Your burnt valves could have been caused by running lean. More likely it was running lean because of the burnt valves. Follow J-Mechs advice and get it running before messing with the jet. The correct way would be with a set of number drills and going one size. I have done the job in a pinch with torch tip cleaners. Now someone help me was marvel the one that had the plastic venturi that would melt down and distort causing all kinds of grief?

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Yea I worked on a 666 some time ago that had the plastic venturi that was all distorted but that was an IH carb. I also saw marvels with the venturi in upside down and causes them to run lean but I am sure this one is in right. I had the carb number wrong its a TSX 934. Thanks for your help.

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