Tuning up the Farmall 400

1956 Farmall 400 gas, recently purchased with rebuilt engine.

Spent the holiday doing tuneup. Points, plugs and carb. Set all to spc per owners manual. Distributor seems tight with minimal sideplay. Took the cover plate off the governor for a look and all internal was clean and appeared to be in good shape visualy.

After tuneup, tractor starts fine, almost immediately on first turnover and ran steady with no flutter and clear exhaust. Tried to check timing. couldn't get the low idle below 600 rpm (looking for 450). tractor cuts out at anything below 550 and stutters bad between 550 & 600. Also, could not get high idle over 1350 rpm. (looking for 1650) I made the adjustments to the idle screw in small increments and worked the throttle after each adjustment.

Not getting the motor to idle slow enough to check timing without the advance kicking in I checked timing at high idle looking for 25° advance. it was relatively close but fluttered about 5° or a bit more ahead and behind the mark. The flutter seemed to be consistent going from just behind to just ahead regularly. Every so often it would hit the 25° mark.

Took the tractor our for a workout with a 7' brushhog in high heavy grass. In first and second gear both motor seemed to pull well under heavy load and the governor seemed to be working. Temperature stayed in the low side of the "run" section of the guage after an hour on a realatively hard pull.

Any ideas on the low idle and high idle issue? I am stumped at this point.

The high idle issue sounds like the governor to carb throttle linkage needs adjustment. To adjust:

- Remove the cover at the top of the governor riser (the slanted cover with the breather tube sticking out of it).

- Remove the cotter from the pivot pin and remove the pin.

- Set the throttle handle wide open.

- Now turn the carb throttle shaft as far clockwise as it will go, lift the governor connecting rod as far as it will go and try to re-insert the pivot pin.

- If the pin does not slide in easily, loosen the locknut on the connecting rod block and adjust it up or down as required until the pin slides in easily.

- Finally tighten the locknut, replace the cotter pin and the riser cover.

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A few degrees of "dither" around the timing mark is pretty much normal for this engine. It's caused by the combined lash of the 5 gears between the crankshaft and the distributor shaft. As long as the engine pulls well under load I'd not worry about it.

I had a suspision it was a governor issue. I didn't want to mess with it until I had some Idea of where and what to adjust. Thanks for the adjustment advice.

also to add to the above advice , there is high and low idle adjustments on the governor once the linkage is adjusted. to get at this need to remove governor housing cover. a manual is helpful here.

I have all the manuals for the 400 except anything on the governor. Everything I have memtioning the governor has an asterisk note saying to "contact the dealer".

Does anyone have a manual with info on the governor?

Your problem at high idle may not be the vertical linkage.
First with the engine off, take the side cover off of the governor and see if the high idle set screw is against the housing. If not you probably have sloppy linkage from the throttle handle to the governor.
Once you get the high idle speed where you want it, then do as was said above and adjust the vertical linkage so the pin just slips in at wide open throttle position.
If your engine has had fire craters installed, it may have the 22 degree advance instead of 25 degree.

Also check the throttle linkage. After years those tractors are bad about loosing movement from the throttle handle up to the governor. When full throttle make sure the governor arm is at it full travel as a first check. Also if the engine stumbles and tries to die when going to slow idle it still needs to be in better tune.
You didn't say how you are checking RPM. Factory tach or other?

Get an IT Manual it tells the whole correct order and way to set everything. Did it on my 650 & W9 they work great now.

For the rough idle check for a vacume leak along with the other ideas and comments. Keep after it and you will have it running like a new one. Good luck. Allan

Well lets start back at the Gov. does the spring flop around in big holes in the two arms?? mover then likely the bushings that USE to be pressed in the arms are long gone and this is not pushing the linkage back to dead ideal . Next as to not getting WOT the rest of the throttle linkage is plum slap wore out from to many year doing what it was suppose to do . Every hole that the linkages goes thru is to big and needs FIXED . Once you have that all tightened up THEn you do the gov to carb adjustment. Then it would be a look at the dist.And that needs done buy some OLD FART that knows how to do this and that has the OLD equipment and knows how to use it as this is becoming a dying art . There are not many of us OLD guys that know how to set the centrifugal advance and correct for ware . I did one of my friends 400 last year and made a new tractor out of it .

First thanks for all the reply's.

I plan on getting bac into this over the next week end. I will get back to you all with what I find.