Need to adjust the thumb pressure on my Bobcat mini excavator

   / Need to adjust the thumb pressure on my Bobcat mini excavator #1  

shameless

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Feb 21, 2024
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Tractor
john deere 3038e
Just installed a thumb on my Bobcat 325. Need to lower the pressure. Where is the adjustment located?
Thanks
 
   / Need to adjust the thumb pressure on my Bobcat mini excavator #2  
First step is to locate your thumbs control valve in your main valve stack and see if it has port relief valves. Usually Allen head set screw and jam nut , that’s where you’ll set the relief pressure for your thumb base end .
You can plug a 5000psi pressure guage into your quick connect that supplies thumb cylinder base port. Read pressure as you operate the close thumb button.
Counter clockwise rotation of set screw reduces pressure, doesn’t take much maybe start with 1/8 turn and check.
Do you have a recommended relief pressure? If not main thing is to just set it less than your thumb cylinder pressure rating.
Here’s a picture of the port relief valve for my thumb cylinder on a Volvo.
 

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   / Need to adjust the thumb pressure on my Bobcat mini excavator
  • Thread Starter
#3  
Yes, mine has the same valve with the set screw. I have to find a socket. It has a 3/4 square locking nut that is very tight. The setting should be 2250. The base port? You mean on the cylinder end that does not have the shaft? This is a lot of help. Thank you.
 
   / Need to adjust the thumb pressure on my Bobcat mini excavator #4  
Yes, mine has the same valve with the set screw. I have to find a socket. It has a 3/4 square locking nut that is very tight. The setting should be 2250. The base port? You mean on the cylinder end that does not have the shaft? This is a lot of help. Thank you.
yes end without shaft. Just want to make sure you’re adjusting the port relief that regulates the base end of thumb cylinder.
My jam nut was 3/4 also. Be a real good idea before you bust the jam nut lose to put a sharpie or paint mark on end of set screw for reference point.
 
 
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