SMTA Carburetor

[Pine Trees]

Been working on a SMTA. I've had the carburetor out, cleaned and painted. I'm trying to install and get the little governor tab in the right place. A half a dozen times I swear I've had the tab lined up but the tractor still roars wide open. I'm beginning to think there is another problem, possibly with the governor. I really think the tab is lined up. Any one have thoughts?

 

[DeltaRed]

I think you still missed the slot.It can be tricky.

 

[Dieselsbest]

As said probably missed again. Not an insult just seems to be how it goes those can be a real PIA

 

[fastfarmall]

So are you leaving the two top bolts really loose, until you feel you have the tang in there,anyway that's the way i do it!!

 

[Pine Trees]

I set the throttle at about half open. Took the carb off. The peg and hole lined up perfectly. Put things back together and the peg fell right in place. Engine roared. Something is strange.

 

[used red MN]

I do not know how easy it would be to do this but you could have screwed the throttle plate on with the plate in the wrong position. As the throttle plate moves to the closed position the stop screw should bump the stop for the shaft. This would be on the side of what I call the ..fat vee.. that the notch is in for throttle shaft tang.

 

[Pine Trees]

Could you explain this a little plainer?

 

[D Slater]

Drop carburetor back off. Loosen the two screws in back top of governor housing throttle shaft. Shaft should move around some and is made to tighten screws after carburetor and tube end at carburetor is mounted. Lift up top of governor cover that has pipe and two screws. Stick carburetor on end of tube and see if butterfly moves with lever at front of tube. You can then see if missing slot or see what problem is. Removing pin at front lever of tube at vertical link helps see if butterfly and front of tube move together. Doesn't hurt to have pin out of link after installing carburetor to check adjustment of the link. Just loosen pipe nut at head and remove the two screws and twist cover to see in top of governor.

 

[used red MN]

When the throttle plate has closed the carb throat or air way passage through the carb that is the idle position. When the governor is told to increase engine RPM the throttle shaft is turned to open the plate to a specific angle. This may be straight up and down to which is the position where the maximum air and fuel are allowed out of the carburetor or wide open. So the plate and shaft has to be able to move from that wide open position to closed or the idle position. The idle stop screw threads into the carb housing through the side of where the governor tube attaches it has a spring on it to hold it in the position it is set. So when the throttle plate is attached to the throttle shaft properly it will turn the shaft to close it. When it closes the side of that ..fat vee.. as I explained in my previous reply rests on the idle stop screw. Likewise when the throttle plate opens the vee moves away from the end of the stop screw. If need be I could talk with you about it over the phone. If you did not remove the throttle plate from the shaft during your rebuild then none of this applies. You will have to email me to exchange numbers I do not want to post my number on the web.
Edit: After reading this I thought I might add. If the plate is attached incorrectly it will not be able to move properly. When installed properly the plate when closed should slightly slope away from the engine. The inner edge that is closest to the engine when the carb is installed should rise up when the throttle is opened.

This post was edited by used red MN on 12/26/2023 at 10:42 am.

 

[used red MN]

I should also add the throttle plate has to be properly centered when attached to the shaft. When tightening the plate to the shaft put in both screws a run them down just snug. Then back them off just a small bit so they allow the plate to just be little loose. Now twist the throttle shaft with one hand so the plate is closing. Then lightly tap the throttle plate with the screwdriver blade. This will center the plate in the bore. While continuing to twist the shaft in the closing position tighten the carb plate screws.