Case 730 Breaking Up/ Running Rough

[cm9]

Hi I have a Case 730 Comfort King that is breaking up under load and at full throttle while sitting. The tractor has run fine up until about two weeks ago when I drained all of the fuel and was going to replace the sediment bowl assembly because the shut off wasn't working. When I took it all apart I found a piece of debris was causing the shut off not to close all the way. I cleaned it all up and put it back together. Ran the tractor for about an hour and had no issues while working it. I was driving to park the tractor and it stumbled a little bit. Ran it a few more times and it has progressively gotten worse. Drained the fuel again yesterday and took it all back apart cleaned everything with carb cleaner and blew out the fuel line. Also sprayed some in the carb. Put it back together and it is even worse. The tractor will run fine at 1/4-1/2 throttle but will start breaking up after that. Tried taking the fuel cap off while its breaking up and no change. If you press in the clutch and throttle it down it will idle fine. Also last year I replaced the following, plugs,wires,cap,rotor,points,condenser and coil. Any help would be appreciated. Thanks, Chris

 

[old]

Time to do a bit of trouble shooting before just guessing at what is going wrong.

#1 check that you have a good blue/white spark at the center wire of the distributor and at all the plug wires that will jump a 1/4 inch gap or more.
#2 pull the carb drain plug and make sure you have a good steady flow of gas that will fil la pint jar in less then 3 minutes and yes catch the gas to look for dirt/rust etc.
#3 when was the last time you serviced the air cleaner and dumped the mud and water out of it and fill with fresh oil.
#4 does choking it hurt of help?? If it helps it is running lean if it hurts it is running rich

Post back if you need more help as to what you find

 

[nick831]

The fact that you were working on the fuel system gives way to the fact that maybe we got some of the debris from the sediment bowl into the carburetor. Have you pulled the carb, disassembled it and cleaned the jets? This might be the problem. Another quick way to dislodge a particle in the carb is to pull the choke while it is running at half or better throttle, push it back in before it dies so you don't have to crank it so much to clear out the unburned fuel. A better option is to pull the rubber hose to the carb from the air cleaner and pop your hand over it when its running. It will suck a particle out of the carb main jet in some cases and save you from having to pull the carb. I would do this after completing everything "old" has told you to do before I chimed in, Good luck. Nick

 

[Bruce from Can.]

Runs good cold , then acts up once it gets hot . Sounds like ignition problems not fuel. Swap the cap and coil and points and condenser. I think if it was a fuel problem. , it would run poorly from the start

 

[cm9]

Thanks for he suggestions. I?ll do some more trouble shooting tomorrow. I also pulled a plug out and will post the pic.

 

[cm9]

It now does it when it is cold.

 

[old]

That plug look a tad bit to black other then the center area which looks about right.

 

[kevinthefixer]

Nobody has mentioned that a tight valve (or a stuck one) could also cause these symptoms. Compression check is in order, if anything is wonky pull the valve cover. If it hasn't been done lately pull the valve cover anyway. Old is right about the plug except that the ceramic looks too white to me, coupled with the soot on the metal parts makes me think either ignition timing retarded or compression problems. Reading plugs is an art, not a science. Another thought: check your condenser, they are getting worse all the time.

 

[cm9]

Updateid a little more troubleshooting today.Checked the spark today and it is fine. Still breaking up but will clear up with some choke. The more throttle you give it the more choke you have to give it so it will run smooth. It will sit and run at idle and with just a little bit of throttle fine while not moving. I will do some more trouble shooting tomorrow.

 

[kevinthefixer]

Don't need to do much more. Your high-speed or "main" mixture is too lean. Turn the larger mixture screw 1/4 turn counter-clockwise; if that doesn't at least help a little, take the carb apart and clean out the main jet. Make sure the gasket is in very good shape, an air leak there can cause this. Take note of which way the venturi tube goes, some can be installed backwards and you'll be worse off. I'm still puzzled why it is worse when hot, should be the other way 'round.

 

[cm9]

Thanks. ... it started out doing it after running for awhile and
now it does it right off the bat. Thanks Again for you help.

 

[old]

If choking helps that means the carb is set to lean or the main jet is clogged up

 

[cm9]

Thank You!

 

[old]

Always happy to help if and when I can

 

[cm9]

Had some time to work on it a bit today. Turned the screw a 1/4 turn and it helped a little but is still breaking up. I guess it's time to take the carb
apart.. Thanks,Chris

 

[kevinthefixer]

Well, give 'er another 1/2 turn first, but you'll probably be doing the carb. Does it have the Zenith or the Marvel-Schebler?

 

[cm9]

Ok i?ll Try that first. It is the Marvel-Scheblee although I can?t
find a number on it just the name unless it?s on the back.

 

[kevinthefixer]

It should be stamped on the brass plug on the opposite side from the fuel inlet.

 

[kevinthefixer]

This is a TSX 749, my tractor is a 1959 model.

 

[cm9]

I turned it up another 1/2 turn and it helped a little. Tractor ran
good and I drove it around a little bit and it was good until I
gave it full throttle then it started acting up again. I cannot find
a number anywhere on the carb. I will post a pic of it. I think I
have it narrowed down to either a TSX785 or a TSX863.

 

[cm9]

Here is my carb:

 

[kevinthefixer]

If you can get it to run good by playing with the mixture screws that's what I'd do, if you rebuild the carb and put the mix back where it was you might have the same problem. And twisting screws is easy and cheap. Also, one guy here on the forum (hight Old) recommends pulling the carb drain and catching a pint jar full of fuel, should fill a pint in about a minute. Also lets you examine the fuel for water, sediment, etc. But you can probably forget troubleshooting the rest of the systems, at least for now, and concentrate on the carb and fuel supply.

 

[cm9]

I am going to try playing with it some more but it didn?t start
running this way until I had taken the fuel bowl off. I will try to
run some fuel through the bowl but I don?t have much
clearance with the steering shaft.

 

[kevinthefixer]

Yeah, I was going to install a drain cock on mine but I don't have any clearance at all there, I have a "power assist" that's about worthless there.

 

[cm9]

I?ll have to try and make something work.