Farmall 400 Surging

pmarkel

Member
This is an update on a problem I was having with my Farmall 400 earlier in the month. Thanks to advice from members of this forum I was able to get the RPM on the 400 to increase (as was repeatedly suggested, the linkages were not moving the lever on the back of the governor enough for the high idle screw to hit its stop). Now I have adjusted/replaced the worn linkages and the tractor definitely has more throttle. However, with the increased RPM I am noticing significant surging from the governor. The tractor is fluctuating a couple hundred RPM with the speed control lever in the same position. Sorry to keep going back to the well, but what causes the engine to surge significantly? Thank you for your time.

Sincerely,

Peter Markel
 
Make sure all the linkage works freely, including the throttle shaft in the carb. Could also be main fuel adjustment set a little too lean.
Have you had a chance to put a load on it? Bob
 
(quoted from post at 21:04:06 08/20/16) Make sure all the linkage works freely, including the throttle shaft in the carb. Could also be main fuel adjustment set a little too lean.
Have you had a chance to put a load on it? Bob
plowed about five acres with it a week ago with 3 16s in clay ground. That was before I was able to give it more throttle though so it labored a bit. I just put the linkages back together yesterday so no work for it yet. I have a new throttle shaft to carb on hand. How difficult is it to replace the old one? Thanks,

Pete.
 
(quoted from post at 04:56:13 08/21/16)
(quoted from post at 21:04:06 08/20/16) Make sure all the linkage works freely, including the throttle shaft in the carb. Could also be main fuel adjustment set a little too lean.
Have you had a chance to put a load on it? Bob
plowed about five acres with it a week ago with 3 16s in clay ground. That was before I was able to give it more throttle though so it labored a bit. I just put the linkages back together yesterday so no work for it yet. I have a new throttle shaft to carb on hand. How difficult is it to replace the old one? Thanks,

Pete.

Replacing a throttle shaft can be easy, or it can be a royal pain. Getting those 2 screws out is the first step. Make sure you have a GOOD screwdriver that is a GOOD fit in the screw slot. Once the screws are out, the throttle plate can be pulled out of the shaft. This might be easy, or it may require a bit of jiggling and wiggling. Your new throttle shaft may be a good fit, or it may not. I've encountered a few that were too large and had to be dressed down, and sometimes the bushing in the carburetor will need replacing and then reamed out to the proper size.
 
Pete, do you mean the horizontal throttle shaft between the governor and the carb? Also, does your new shaft have the hole for the pin that goes through the bronze lever at the front? Bob
 
(quoted from post at 19:09:35 08/22/16) Pete, do you mean the horizontal throttle shaft between the governor and the carb? Also, does your new shaft have the hole for the pin that goes through the bronze lever at the front? Bob
es, that's the one. I took that out and examined it but honestly the wear appeared to be minimal so I put it back in as is and the surging went away. I am pretty sure that when I was working on the governor last week I loosened that shaft and got it out of position so that the carb end of the shaft was not seated correctly. Surging seems to be gone but I drove the tractor over to a guy who fixes starters because the starter keeps giving me trouble. So for now that's all. I would like to thank all members of the forum for their assistance.

Sincerely,

Peter Markel
 

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