706 engine stumbles when throttle is advanced.

I have had this annoying issue with this tractor for 4 years, I have never looked into it until now. 706 gas, mainly used for loader work. I have never really worked it hard, about 800 hrs on a rebuild.

If I give it too much throttle at once the engine will stumble and sometimes die. By to much throttle I mean if I don't bump the lever with my hand 1/4 of an inch at a time it will stumble. Seems to do it more when cold, but it never goes away even if I work it for extended periods of time. It will also stumble when I let out the clutch to fast in H3 or H4. I almost never use these two gears anyway way to fast for loader work but now I am driving on the road more. My 450 takes off from a stopped position in road gear better than the 706 does in H3 low TA. Other than this problem there don't appear to be any other issues, seems to have plenty of power and the governor works fine as far as I can tell.

Put a new coil, wires, plugs, points and dist. cap on this spring and the problem persists. I did all of this because the wires had massive amounts of corrosion on the ends and ruined the cap and coil, causing a no start situation. I have plenty of fuel getting to the carb.

Thanks
Nate

Richen the idle circuit about 1/4 turn. If that doesn't help, put it back and richen the main jet about 1/8 turn. May have to try a little more on each until it works like you want.

If it will pull a continuous heavy load with out a problem for at least 5 minutes you can forget about carburetor problems. Adjusting the idle mixture might help but I doubt it. Main jet is fixed so if you have an adjustable needle on main jet, be it electric shut off or just manual needle, make sure it is turned out five full turns.
I would bet your manifold heat riser is not functioning and the intake manifold heat stove inside is full of carbon from years of use. Those engines are noted for being (cold blooded) and if that heat riser is not in good working condition you will have a spitting sputtering son of a gun. Counter weight needs to stand straight up and down under spring tension and be free to move forward near 90 degrees but that doesn't tell you if insides are plugged up.
Also, if 263 engine 22 degree spark advance at full throttle, 291 18 degrees.

Uncle Mike about his 706 "that cold natured SOB would freeze up on the equator in mid July!"

I'm with pete. The next simple try is higher octane fuel.

So, how's higher octane/harder to ignite fuel gonna help a "stumble"? Inquiring mind(s) wanna know!

Not sure about the physics but, I had a 706 that would stumble and fall under, albeit under load. After having tried about everything else, I drained the regular fuel and put premium fuel in. That cured my problem. Just something to try that doesn't cost any money to speak of.