SMTA throttle

[Dave H (MI)]

The SMTA that I have used for hay the last 20 plus years developed a problem where the hand throttle would slip back to idle over and over. It always has done it to some degree but this was constant. The tooth that engages in the notches above it had worn completely off so I replaced it with a new unit. Still slipping a lot. It will stay in place at about 3/4 but that is a problem for the haybine...not enough power... so I have to hold the handle constantly while mowing and that is really not a solution. Anyone have any idea what the issue might be and a good way to resolve it either temporarily so I can finish and then permanently? Is there an adjustment to the linkage that will allow me full RPM's and not pull so hard on the lever? It's a wonderful tractor to cut small fields with.

 

[Janicholson]

The SMTA that I have used for hay the last 20 plus years developed a problem where the hand throttle would slip back to idle over and over. It always has done it to some degree but this was constant. The tooth that engages in the notches above it had worn completely off so I replaced it with a new unit. Still slipping a lot. It will stay in place at about 3/4 but that is a problem for the haybine...not enough power... so I have to hold the handle constantly while mowing and that is really not a solution. Anyone have any idea what the issue might be and a good way to resolve it either temporarily so I can finish and then permanently? Is there an adjustment to the linkage that will allow me full RPM's and not pull so hard on the lever? It's a wonderful tractor to cut small fields with.

Three solutions:
Replace the entire hand throttle lever and notched cover plate with a friction style lever after market
For example this on Ebay-- https://www.ebay.com/itm/2860077013...1291&msclkid=063afb471ba61ee58e0e9da6d1833ebd
Or you can use a triangular file and re shape each notch.
Or you can purchase a new Notch style that looks like the old one from this site (Item #: 114409, Ref: 51351DBXA) $70.00
Jim

 

[used red MN]

I believe the spring that is under the notched cover can be tightened to hold the lever more firmly up so the teeth are held engaged by more pressure. There is a point that the pressure needed to disengage the teeth by pushing down the throttle handle becomes an annoying amount of resistance.

 

[Absent Minded Farmer]

I believe the spring that is under the notched cover can be tightened to hold the lever more firmly up so the teeth are held engaged by more pressure. There is a point that the pressure needed to disengage the teeth by pushing down the throttle handle becomes an annoying amount of resistance.

There's no adjustment on the one I had that wouldn't hold. Ended up pulling the cotter & adding a thin shim washer. It did the trick. They can also wear crooked & you have to pull the handle & give it just the slightest twist in a vise to get it to sit right in the notches.

Mike

 

[Fritz Maurer]

Hook a booster spring to one of the head bolts and attach the other end to the top of the bellcrank under the hood. Set it up so that the spring is stretched at idle. Make a L bracket to go under the head bolt with a little hole in it to attach the spring.

 

[caterpillar guy]

The tooth on the throttle lever is worn off from just pulling the lever back without pushing it down slightly. We welded a new set of notches to the outside of the round cap like plate then welded a piece on the lever to match up with the notches and works fine just is not as fine of an adjustment to the throttle as it was originally. You can do as we did or buy one of those friction levers to replace your original. About the choices you have. The spring tension increase is not going to last very long if it is worn enough to slip back.

 

[BarnyardEngineering]

Nothing's "wrong," just normal wear and tear. You're working against the governor spring on the tractor which is always trying to pull the throttle to idle. It's doing its job as designed.

Original on these tractors was a "sawtooth" and those wore out quickly. An aftermarket "square notch" control was much better but after 75 years... Just replacing the tooth on the handle leaves the worn notches.

The friction style linked above was the final aftermarket solution. I did not know they were still available new. I had hoped to pick one up for my Super H at the Red Power Showdown back in June but nobody had any.

 

[Gwiz]

The SMTA that I have used for hay the last 20 plus years developed a problem where the hand throttle would slip back to idle over and over. It always has done it to some degree but this was constant. The tooth that engages in the notches above it had worn completely off so I replaced it with a new unit. Still slipping a lot. It will stay in place at about 3/4 but that is a problem for the haybine...not enough power... so I have to hold the handle constantly while mowing and that is really not a solution. Anyone have any idea what the issue might be and a good way to resolve it either temporarily so I can finish and then permanently? Is there an adjustment to the linkage that will allow me full RPM's and not pull so hard on the lever? It's a wonderful tractor to cut small fields with.

The friction levers are sweet, but not if you want to look original.
The hole/rod where the throttle lever pivots gets worn out-of-round after so many years. This allows the lever to twist and slip out of the notched plate. Haven't done it yet, but intend to remove mine, weld and re-drill the hole eventually. A better fix than bending the lever as mentioned above. A new spring holding the lever up would likely help as well.

 

[never too many tractors]

friction levers are my favorite. I have one on it and its the best.

 

[Tired54IH]

I have two SMTAs with friction type and I like them. My levers are made by M&W and to me, are collectable.

 

[D Slater]

IH started square tooth throttles on SMTA serial 71817 and SH 26561. Never cared for them myself to far between settings. Used the friction type but found if using wide open in field they will start vibrating down unless friction disc is set so tight lever pulls the post back and forth when moving. Went to using a helper spring on throttle linkage set stiff enough that it will barely keep at idle.