IH 574 Gas - Popping Under Load - At my wit's end

Hi all!

Like the title says I've got an IH 574 with the gas c200 engine and a TSX 959 carburetor. About 6 months ago the tractor would start popping when it went under load and then a lot of cases would almost gag itself completely out. I went to looking for what happened and I haven't found anything. I've rebuilt the carburetor three times, verified played with the timing at least three different times, I put a new head gasket on it because a couple of the bolts had loosened and I did see a little bubble come out once. I put a new coil on, I put new wires on, I switched back and forth between a new electronic and new mechanical ignition, I ran new wires to the coil and from the switch to the starter solenoid, and I've replaced the spark plugs three times because they foul out rather quickly Now. I put a new air filter in, I put new boots to the carburetor, new gaskets on the intake and new gaskets between the carburetor and the intake. I run only clean not ethanol higher octane gas. There is a problem with the carburetor that I've not been able to solve and that's that it will drip a little if you don't shut the gas off. I've tried multiple needles and seats and it still does the same thing which drives me crazy. It doesn't drip while you're running it. Just when it's sitting and shut off after a while a drip will form.

So in the end I seemingly have good electric, good ignition, good air flow, good gas going to the pump and pumping like crazy, and I've got a carburetor that's clean and the damn thing still will barely start most of the time. If you do get it started and pull back on the throttle it'll gag itself out all the while popping and spitting and sputtering and carrying on. I should also note that the engine was completely rebuilt 400 hours ago.

Anyone have any ideas aside from pushing this thing into a ditch? I was going to post a video but I can't even get it started. I'll try again later after I clean the plugs again.

Have you timed the ignition precisely and taken a look at the centrifugal spark advance, then verified it's operation with a timing light?

As to the carburetor, the inlet valve seat has to be TIGHT in the carburetor body or gas will sneak past it's gasket.

Is the float in good condition, no liquid inside?

Also, if someone in the past has repaired the float with excess solder it will be ''heavy'' and not apply as much pressure as it should to the inlet valve needle.

You set the valve lash clearances correctly after installing the head gasket? If after checking into what wore out posted about the distributor and that does not fix it . I would suggest taking a compression test. Depending on what that shows I would pull the valve cover and check for bent push rods, although this should have been discovered while the head was off. Next I would pull the coil wire and crank it with the starter watching the valves to see if any are not moving the same distance as the rest. If one or more is not you have a flat cam which is a term for worn off lobe.

As one guy said valves need adjusted or you have a bunch of carbon build up on a valve or 2 or a burnt valve

If it's a steady popping back through the carb, worse under load, that indicates an exhaust valve not fully opening. Could be a flat cam, bent pushrod, pushrod jumped off the ball, the adjustment backed off, broken rocker arm.

I have seen one case of an exhaust port completely blocked with carbon, which would cause the same symptom.

Have you had the plug wires off prior to it acting up. If so does the distributor rotate clockwise or counter clockwise and MAKE SURE your timing order is correct with the rotation of the distributor. I have a MF 230 acting very similar to yours and discovered the rotation of distributor was counter clockwise but I had the wires on to match a clockwise rotation. I kicked myself in the rear for not catching it sooner.
I had checked the timing with a light but I could get it to run better by just playing with the timing.
if you have it wired up for 1-3-4-2 clockwise rotation but it is counter clockwise it is firing 1-2-4-3, it will run but not very well.

if gas is leaking it does not sound like the carb is correct in its function. if only a problem under load is the governor working correctly?