Bobcat 763 #512216380

[shadesofidaho]

Can the lift spool seals be changed with out removing the body ? Thanks Joe

 

[Rojas]

In a word, yes. And there is no need to remove the detent cover when you pull the spool as well. I did both spools while I had access and everything clean. New boots and o-rings as well. I'd get some extra seals for spares. The only source is Bobcat and sometimes those guys are fishing when I need to work.

 

[Tazza]

In a word, yes. And there is no need to remove the detent cover when you pull the spool as well. I did both spools while I had access and everything clean. New boots and o-rings as well. I'd get some extra seals for spares. The only source is Bobcat and sometimes those guys are fishing when I need to work.

Not all the seals are dealer only.... The boots yes, the O rings and quad rings can be bought from a hydraulic seal shop and a good price.
With that said, when i get to re-building my control block i think i'm going to throw a genuine seal kit at it so i don't need to touch it again. I don't need that rotten thing to leak on me.
Yes, be careful with the detent balls and spring behind that alloy cap. They come out at a pretty good speed! Then you need to get them back in that cap.

 

[thetool]

Not all the seals are dealer only.... The boots yes, the O rings and quad rings can be bought from a hydraulic seal shop and a good price.
With that said, when i get to re-building my control block i think i'm going to throw a genuine seal kit at it so i don't need to touch it again. I don't need that rotten thing to leak on me.
Yes, be careful with the detent balls and spring behind that alloy cap. They come out at a pretty good speed! Then you need to get them back in that cap.

Back when I first started wrenching on Bobcats the 743b was the current production model. The main control valve was such a pain to get out, and resealing them was a common task. We used to cap all the ports and pressurize the resealed valve with 10 psi air and put it in a bucket of water and look for bubble trails.
When the C-series machines came out, the valves were easier to pull, but it seems also that the leaky valve problem came less often.

 

[Tazza]

Back when I first started wrenching on Bobcats the 743b was the current production model. The main control valve was such a pain to get out, and resealing them was a common task. We used to cap all the ports and pressurize the resealed valve with 10 psi air and put it in a bucket of water and look for bubble trails.
When the C-series machines came out, the valves were easier to pull, but it seems also that the leaky valve problem came less often.

Thats an intersting way to test it... I have my 763 waiting to be pulled down and worked on, the control block does look much easier to pull than the 743 ones!
Any other tips on what to do to help prevent problems?
I know for ram sticks when they are shiny you need to roughen them up a little to get a good seal. Like engine cylinders, if they are glazed they don't hold the pressure between the piston and rings. When i need to do it, i spin it in the lathe and use wet and dry running it up and down fot the cross hatch pattern. I'm a little worried to do that on a spool though, i'd only touch the section where it seals, not inside the main ports. If i stuff up on a ram rod i'm up for $20, if i do that on a control block, multiply that by 100.

 

[thetool]

Thats an intersting way to test it... I have my 763 waiting to be pulled down and worked on, the control block does look much easier to pull than the 743 ones!
Any other tips on what to do to help prevent problems?
I know for ram sticks when they are shiny you need to roughen them up a little to get a good seal. Like engine cylinders, if they are glazed they don't hold the pressure between the piston and rings. When i need to do it, i spin it in the lathe and use wet and dry running it up and down fot the cross hatch pattern. I'm a little worried to do that on a spool though, i'd only touch the section where it seals, not inside the main ports. If i stuff up on a ram rod i'm up for $20, if i do that on a control block, multiply that by 100.

A fine cross-hatch on a sealing surface against a polyethyene seal works, but on control valve spools that surface is only about a half-inch band somewhere near the ends of the spool, probably very difficult to do.
But if anybody can do it, I'm sure you can...=). I'd be interested to know about it if you ever give that a try.
I know a guy that had a stuck spool, so he got a new spool. He cut a groove down the middle of the old spool, lengthwise. He made a drive wire to hook into the spool eye, put some lapping compound on the spool and had at it with a drill. Then he put it all back together with the new spool and it worked fine. He was told he needed a new main control valve, but he only needed a new spool.
I sometimes wonder if he just got lucky, but what did he have to loose except the time of maybe pulling the valve twice?. And a spool, I guess.

 

[Tazza]

A fine cross-hatch on a sealing surface against a polyethyene seal works, but on control valve spools that surface is only about a half-inch band somewhere near the ends of the spool, probably very difficult to do.
But if anybody can do it, I'm sure you can...=). I'd be interested to know about it if you ever give that a try.
I know a guy that had a stuck spool, so he got a new spool. He cut a groove down the middle of the old spool, lengthwise. He made a drive wire to hook into the spool eye, put some lapping compound on the spool and had at it with a drill. Then he put it all back together with the new spool and it worked fine. He was told he needed a new main control valve, but he only needed a new spool.
I sometimes wonder if he just got lucky, but what did he have to loose except the time of maybe pulling the valve twice?. And a spool, I guess.

I remember a leaky control block i had, i talked to a machinist friend about it and he said worst case you can lap the inside of the block and make a new spool to suit. His was was close to you mate. He said to get a length of cast iron, drill it and cut 2 slots in it to allow it to expand when you tighten up a bolt through the middle. Use lapping compound and run it through it. Tighten it every so often to take up the slack. Machine a new spool and grind to the rite size. The leaking problem was actually leaking load check seals!!! Replaced them and it was spot on.
I do have the gear to roughen the sealing surfaces but i don't want to tempt fate I do have a problem with the spools on my hoe, so i may give it a go on them yet.. Worst case they leak a little (more) when i use it, but easy to clean up.