L4740 HST Idle RPM

[Rockin' G Ranch]

I checked the "Auto Throttle Advance" and honestly can't tell that it does anything if it is "On" or "Off". The linkage actually appears to do absolutely nothing. The cable only moves a fraction of an inch from "Off" to "On". Is that normal???
I can't find any way to reduce the idle RPM. How is the idle adjusted?

 

[beppington]

A 2,000 RPM idle is way too high. After warm up, 2,000 is where I increase mine to for almost everything I use the tractor for!

Have you checked to see if you can manually move the throttle by pushing the throttle piece itself on the side of the engine? (see pic below)

Maybe a stuck/ seized throttle cable(s)?

Maybe your Auto Throttle linkage underneath the HST pedal is jammed up or bent. On mine, the Auto Throttle engagement/ linkage is purely mechanical, not electrical or computer. Your throttle must be at idle when you engage the Auto Throttle (a peg must enter a hole while lined up) ... & if the throttle isn't at idle & someone prior to you tried to engage Auto Throttle anyway, aka jam it in anyway, it looks bend-able to me. It may be bent.

The piece at far-right that the 2 cables are connected to ... Can you move it back & forth, left & right? If so, & the actual cables don't move, aka slide within their sleeves, the cables may be seized up. If no, it's beyond my knowledge.

 

[Rockin' G Ranch]

beppington,
Thanks! OK, I can move the piece at far-right that the 2 cables are connected to (in your picture) and the idle goes down to ~800 RPM. However, when I speed it up with the accellerator linkage on the steering column it speeds up but does not go back to 800 RPM when I move it back the other way. The cable is connected so that it can speed it up but does not move the piece to the right to slow it back down. Should that piece that the cables are attached to have a spring on it to pull it back to idle?
BTW, what is the other cable for???

 

[beppington]

beppington,
Thanks! OK, I can move the piece at far-right that the 2 cables are connected to (in your picture) and the idle goes down to ~800 RPM. However, when I speed it up with the accellerator linkage on the steering column it speeds up but does not go back to 800 RPM when I move it back the other way. The cable is connected so that it can speed it up but does not move the piece to the right to slow it back down. Should that piece that the cables are attached to have a spring on it to pull it back to idle?

Yes! A spring pulls the throttle (piece at right) back to bottom, aka idle speed.

BTW, what is the other cable for???

One cable is a throttle cable going to the throttle lever on the steering column. The other cable is the throttle cable going to the Auto Throttle connection point I mentioned under the HST pedal. Either cable can accelerate your engine.

So ... Probably your throttle's spring is missing (most likely) or worn out (less likely), or either one or both of the cables are sticking (least likely IMO).

With the tractor OFF, with your right hand pull the throttle (piece at right) wide open (to the left), & with your left hand see if the cables both seem to move freely within their cable jacket.

If they do, must be a throttle spring problem I mentioned.

 

[Rockin' G Ranch]

Yes! A spring pulls the throttle (piece at right) back to bottom, aka idle speed.



One cable is a throttle cable going to the throttle lever on the steering column. The other cable is the throttle cable going to the Auto Throttle connection point I mentioned under the HST pedal. Either cable can accelerate your engine.

So ... Probably your throttle's spring is missing (most likely) or worn out (less likely), or either one or both of the cables are sticking (least likely IMO).

With the tractor OFF, with your right hand pull the throttle (piece at right) wide open (to the left), & with your left hand see if the cables both seem to move freely within their cable jacket.If they do, must be a throttle spring problem I mentioned.

I did your test and both cables are free. They just have a ball at the end so a spring must have to pull it back to idle. Where should the spring be located? I don't see a spring anywhere. Thanks for your help!

 

[beppington]

I did your test and both cables are free. They just have a ball at the end so a spring must have to pull it back to idle. Where should the spring be located? I don't see a spring anywhere. Thanks for your help!

Unfortunately I haven't had the need so far to determine where the spring is.

If it's anything like other motors, you should be able to see it to the right of, or behind, the throttle piece at right in the pic. I really don't know, though - Maybe somebody else can jump in here ...?

 

[Rockin' G Ranch]

Found the return spring location. Item 110 in picture. Now I just need to take it apart and fix it. Thanks for all of the help.

 

[Rockin' G Ranch]

Wasn't the return spring afterall..... Got to fooling with it and found the ATA cable was sticking. I put oil on it and worked it back and forth until it loosened up. All is working great now. The idle speed is 800 RPM.
Thanks for the help. This forum is great for getting help such as this!

 

[beppington]

Wasn't the return spring afterall..... Got to fooling with it and found the ATA cable was sticking. I put oil on it and worked it back and forth until it loosened up. All is working great now. The idle speed is 800 RPM.
Thanks for the help. This forum is great for getting help such as this!

Great news! :thumbsup: