Need help with ford 640 surging under load

[hjnash]

The tractor will work Ok for about 20 minuets after adjusting the new carb main and idle valves. This started as soon as we tried using the tractor a few months ago, sat most of the LONG winter. So at this point I have a new carburetor, points, plugs, cap and rotor. I bought a good vacuum gauge and a meter for RPM and Dwell. So idle at 550 RPM vacuum reading 14 to 18
idle is smooth. I tried 4 different ways to start the main and idle adjustments. but the tractor still increases my speed
on small hill of just two feet. When I am running the 5 foot bush hog the tractor over reves when I het tall grass and tried to almost stop when I go down hill. Today I set the main so it ran 1200 RPM and I could tell it was burnning rich. I still had seurging. I can change throtel from idle 550RPM to almost 1200 RPM with not problem so I dont think the governor is bad.
Any help on this I would greatly appreciate.
Thank You

 

[Sean in PA]

Sounds like the governor is worn or the linkage is out of adjustment.

 

[hjnash]

Thanks Sean, today I mowed with the governor disconnected, the carb was connected to
the tractor throtal and it ran fine. so I am going to first try adjusting the governor linkage and
if that is not the fix I will look up how to replace the Governor.

 

[showcrop]

I am not sure that I understand what you have posted. But anyway, set your low speed jet, which is really adjusting air, not gas, to one and a half turns. Set the high speed to 2.5 turns. Don't ever try to adjust the high speed except by small increments with a heavy load on it. At your 550 idle speed, try adjusting the low speed jet to see if you can get the RPMs to increase. If it increases, turn it down with the idle adjustment. Your owners manual has a very good explanation of adjusting the governor linkage. Don't dig into the governor until you are sure about the carburetor and the governor linkage.

 

[hjnash]

Thanks all, I think it is fixed, First I did adjust the governor that helped a lot.
I was having a hard time finding timing mark, but I finally did and changed timing.
but still had more surging than I wanted. I turned the main jet in to on half turn from
all the way in. I started heavy bush hoging and made small changes out till no surging.
as it turned out My carb works best with the main out 1 1/4 turns. So yesterday mowed allmost two hours
5 foot weeds ran so good.