Question for Tazza

[Tazza]

Ok so switched the valves (replenishing) and still no improvement so like you said I now have switched the drive motors and the problem followed the drive motor, I took it back apart and all looked good, blew air and cleaned the entire assembly and re-assembled with the new seal kit again, tested and still weak driving foward then hits hard and turns. When the motor was on the other side revers was the same way ( to be expected right? ) so the question is there is a small brass disc on 1 of the inside surfaces that I think controls pressure, it seems to fit loose could this cause the pressure drop I am having? the drive motor has a ton of power in 1 direction so I want to belive the geo assembly is good, any thoughts?

Did you check the shuttle valve as well? it is behind the allen headed plug near the high pressure ports. If it's stuck, i guess it can cause this problem.
At least you now know it is the motor, not pump.

 

[cumminsguy]

Did you check the shuttle valve as well? it is behind the allen headed plug near the high pressure ports. If it's stuck, i guess it can cause this problem.
At least you now know it is the motor, not pump.

Yep re-placed the shuttle, valve and springs and popetts, didn't help I'll keep you up to date on what fixes it.

 

[cumminsguy]

Yep re-placed the shuttle, valve and springs and popetts, didn't help I'll keep you up to date on what fixes it.

The problem has been solved. So the issue ended up being that the poppets and shuttle valve had not been closing propperly due to wear on the body of the drive motor, (the area the poppet seats against) housing casting. So nothing i did would solve the issue without re-machining the area to remove the grooves that had worn into it. The shuttle valve has to slide back and forth and seal in each direction to allow oil to flow and create pressure for the foward and reverse motion, so if the seal is not good then pressure is lost and drive is weak or erratic, this can happen in 1 direction and the other direction seals good and the drive in that direction will be good. I had tried new poppets and shuttle valve but the wear was also in the housing so that didn't work. In the end I turned to the guys and girls at LPS to provide me with a replacement re-man drive motor, they are real nice people with great knowledge and helped me understand the whole shuttle valve function. My 743b is now back in action and with the help from Tazza and LPS I now know alot more about my Bobcat, Thanks Guys you have been a great help, Tom

 

[Tazza]

The problem has been solved. So the issue ended up being that the poppets and shuttle valve had not been closing propperly due to wear on the body of the drive motor, (the area the poppet seats against) housing casting. So nothing i did would solve the issue without re-machining the area to remove the grooves that had worn into it. The shuttle valve has to slide back and forth and seal in each direction to allow oil to flow and create pressure for the foward and reverse motion, so if the seal is not good then pressure is lost and drive is weak or erratic, this can happen in 1 direction and the other direction seals good and the drive in that direction will be good. I had tried new poppets and shuttle valve but the wear was also in the housing so that didn't work. In the end I turned to the guys and girls at LPS to provide me with a replacement re-man drive motor, they are real nice people with great knowledge and helped me understand the whole shuttle valve function. My 743b is now back in action and with the help from Tazza and LPS I now know alot more about my Bobcat, Thanks Guys you have been a great help, Tom

I'd have never thought the shuttle valve seat would have worn so badly to cause it to not seal enough to cause your issue. At least it is now fixed, LPS do know their stuff inside and out.