50 model fordson dextra

Just bought this the throttle does not work it is moving the butterfly no reaspose tractor starts but at full rpm u have to pull the kill knob to lower rpm and half way is half throttle all the way kills it like it should wat do I need to do to fix it right

Something is up with the governor.

First, look at the linkage. The governor arm should be linked directly to the carb throttle lever.

Second, the lever on the dash, (the speed control lever) is connected to the governor arm with a spring. At idle, the spring is in the relaxed position. When the lever is pushed to the fast position, the spring is pulled tighter.

Inside the governor housing are a set of weights. The faster the engine runs, the faster the weights spin, the harder the arm pushes against the spring and wants to close the throttle.

So, the spring from the dash lever wants to pull the throttle open, the weights in the governor want to push it closed. With the engine running. there is a balancing act between the two forces that control the engine speed.

Start with the engine off, dash lever at idle. The throttle plate will be open or partially open, and can be pushed closed with minimal effort. The governor arm should travel freely the full range from throttle closed to wide open without binding or having excess slack or wear in any component.

Now move the dash lever to the fast position. The throttle should be spring loaded to the wide open position. You should be able to push it closed with moderate finger pressure, then it will spring back to full open when released.

If everything checks out, set the throttle at idle and start the engine. If it still over revs and the governor does not push the throttle closed, either something is wrong internally with the governor, or the linkage between the gov and carb is too short, running out of travel before the throttle is closed.

Once everything is adjusted and working properly the engine RPM should be 2000-2200.

Hi
I'm Gonna take an educated guess from what you said it's a diesel tractor? if so it has the option of 2 types of fuel injection pump. The first and most likely for your tractor is a vacuum governed type. It should have 2 small brake hose sized steel lines running from by that butterfly down to a small housing held together with 4 bolts on the front or rear of the pump. inside that is a diaphragm, that senses vacuum in the manifold as the flap opens and closes. Revving it up or down

This is then attached to the fuel delivery rack in the pump, to make that do what ever it senses.
it sounds to me like that Diaphragm May have a split or hole in. then it is not moving the rack as it should, the other thing could be there is a damper spring in that housing, maybe that has fallen apart and jams the rack in a flat out position. Then when you pull the stop it forces the rack to move back to low revs then stop.

sometimes the rack rod rusts and sticks to, that can cause interesting start and run problems as well. To gain access to that there should be a side plate, remove that and you can see the pump elements and the control rod. it should move pretty free by a little more than finger pressure, and return on it's own.

Make sure the pump outer is clean you don't want grit and junk in there with that cover off. Do not adjust anything in there it will mess the settings up for the pump. Just lubricate and gently free the rack if needed. I have done a few of the 4 cylinder type pumps on majors and kinda know the limit of to much force and what to do.

The other type pump doesn't have the 2 lines it is gears/ centrifugal weights in the end of the pump in a housing with oil lubrication.
The rack part of that can stick the same but the governor part could be messed up and you can't really do anything other than getting a diesel shop to look at it.

Another thought for both pumps is that the excess fuel button could be stuck in. it is a push button on the bottom of the stop arm, it should come through the pivot point in the bottom of the arm, with a little round pill shaped end on it or could be you push the stop lever in sideways and it clicks in. both types should pop out when the motor starts. if it is in ,it allows the pump rack to come back to wide open, which would give you the full revs, then the stop lever being pulled would shut the revs or stop it. Some times the button is missing and just a small rod pokes out the stop arm about a 1/4 inch or so a test is with the motor stopped push that button in, then pull the stop lever out, that button or stop arm should pop out if it's working right and depending on excess fuel linkage type .
Hope this helps some the pumps are pretty well the same design as the major, but never worked on the Dexta ones and only driven 1 in my lifetime.
Regards Robert

It sounds like your Dexta has the 3 cylinder diesel.
If so, it has a vacuum governor, unless its a '63 or '64 model which had mechanical governors.
Your governor diaphragm probably has a tear in it, which is a very common problem, especially if the tractor hasn't been run for a while. You can buy a new diaphragm from the parts section of this site.

Robert is exactly right on the governor, the DEXTA came out in 1957 to 1962 with a vacuum governor and all your symptoms point to a hole in the governor diaphragm.

Not a bad job if you take it slowly, the worst bit is getting the diaphragm hooked up to the rack but this is only a fiddly thing.

I think that YT sell the governor diaphragm.

Thankyou sir and I'm sorry yes its a 3 cylinder Perkins diesel

Yes its a 3 cylinder Perkins sorry I forgot to add that and thankyou for ur time

Would you please drop out the R? It is DEXTA and NOT DEXTRA. That just makes a lot see red with high blood pressure.