JD 790 PTO Adjustment

[beenthere]

Hi everyone!

This is my first time posting here. And as the title says I own it, JD 790 Which I recently inherited.

Problem: PTO engages without an implement, but grinds and does not with an implement. In fact, i'm having the same exact issue as this post below.

problems with pto my jd 790, 5' rotary cutter mower

when I connect the rotary cutter mower the pto not engage. It makes noise.when I disconnect works great thanks:thumbdown:

www.tractorbynet.com

What I tried: I've used the manual and made the suggested "free to the top" clutch adjustment, Which I assume means the amount of play in the clutch before resistance. But that didn't seem to help. As for the post up above, I reached out to @Robfnk about how he did the PTO adjustment. He gave me some pointers but suggested contacting someone as to the steps how, because there may be a better way to rotate and identify the bolts needing adjusted. The pictures attached I believe are where adjustments need to be made, And the bolt(s) gap .06.

Thanks!

The pics you posted in the opening post are the openings that I believe you need to go through to adjust the two clutches.
You should poke around until you find the manual (not likely in the operators manual, but the service tech manual) or a video that discusses the clutch adjustment, and not just the pedal adjustment.

Also, let us know if the PTO stops turning after the clutch is fully depressed when attached to a mower or other attachment. And will the tractor start with PTO engaged ?

 

[svohio]

@beenthere I'm currently at work but I will make it a point this afternoon to answer your latter question about whether the PTO disengages with the pedal fully down. I did discover I downloaded technical manual for the 790 which I accidentally thought was actually the Operators manual. So I will look over that this afternoon as well.

 

[svohio]

@beenthere I've been reading the technical manual and this adjustment falls in line with the video (see attachment).

 

[svohio]

I made adjustments according to the technical manual from a range of 5/8 to 7/8. I engaged the PTO with a slight grind noise which was less than before and released the pedal and it would spin. However when I depress the clutch pedal fully the PTO remains spinning. Additionally I still can't engage the PTO with an implement attached, only when there's no Implement attached.

 

[Harry in Ky]

You're describing pedal free play adjustment. What does you manual have on the internal adjustment? Assuming you've been there? Have you tried this? Working through the internal adjustment access hole, wedge a pry bar in the clutch/flywheel assembly to prevent the engine from turning. Block the clutch pedal fully down and engage the PTO. Now put a pipe wrench and cheater pipe on the PTO output shaft and see how much effort it takes to turn the shaft (or if you can even turn it). If you can't break it loose that way, you can adjust back and forth all day and it's not going to work properly.

 

[svohio]

You're describing pedal free play adjustment. What does you manual have on the internal adjustment? Assuming you've been there? Have you tried this? Working through the internal adjustment access hole, wedge a pry bar in the clutch/flywheel assembly to prevent the engine from turning. Block the clutch pedal fully down and engage the PTO. Now put a pipe wrench and cheater pipe on the PTO output shaft and see how much effort it takes to turn the shaft (or if you can even turn it). If you can't break it loose that way, you can adjust back and forth all day and it's not going to work properly.

I started with adjusting the free play because it was so extremely out of adjustment according to the technical manual that it may not be allowing the PTO clutch to stop spinning. I could not find anything on internal adjustments of the clutch, just the assembly and disassembly, and how it's engaged and disengaged. I'll be able to try your recommendation tomorrow. Other suggestions were to do something similar like a screwdriver to rotate the PTO clutch and adjust the gap on the three bolts associated with it to .055 - .06.

I'm oblivious to the clutch assembly and so I just want to proceed with caution. So anything anybody can suggest here is helpful because we just can't afford.

 

[beenthere]

Harry in KY said it well, if it is true that the PTO clutch disks are stuck together. It may help.

You said you had downloaded the service tech manual. The dual clutch adjustment (not the pedal linkage) should be in that manual.
Post a link to it here if you can. Maybe we can lead you from there. You get at the adjustment nuts through the port holes shown in your first post. You have to rotate the flywheel/engine to get at the three adjustment points.

 

[JimRB]

When I adjusted my PTO clutch bolts I marked the first bolt I adjusted with chalk. The second bolt had a marking already and then I made few marks for the third bolt. Now when pressing the clutch I feel the PTO clutch about halfway down. It was barely feeling the PTO clutch before.

Yes when the PTO is properly adjusted I still have to wait a bit for the PTO shaft to stop, or slow down. The mower, the brush cutter or the chipper will all grind gears if I do not wait long enough for things to slow down. I might fix this if I wanted to split the tractor, clean the two output shafts and lube up friction points and splines. But that is a few days of work as slow as I am. I might get another 1,300 hours out of the main clutch disk if I do not have much dirt moving work.