Jerky lift cylinder Bobcat 743

[Al Miles]

The tilt cylinder works smoothly but the lift seems to stick then drop or raise too fast. Almost like it's going into float.
When I push on the top or bottom of the pedal it seems to stick then pops free. Almost lost a log off the forks a few times.
I checked the linkage and it is free. Could the valve spool be sticking or is there a pressure relief valve in there somewhere that could cause this?
I encountered this problem a couple of years ago but it went away as quickly as it started, this time it started to act up about 10 hours of operation ago. Thing is it's not every time I raise or lower the bucket, one time it works well the next it.s jerky.
Any Ideas?

Al.

 

[crewchief888]

could be some rust in the lift detent cap causing the problem.
could be that the linkage is binding on the pivot on top of the chaincase or rusted linkage where the arm connects to the spool.

 

[Al Miles]

Thank you,
I checked and lubed all the linkage.
The detent cap? Is that something that I can get at with the valve in place?
Al

 

[crewchief888]

Thank you,
I checked and lubed all the linkage.
The detent cap? Is that something that I can get at with the valve in place?
Al

if you open the tailgate and look forward past the blower housing to the rh side of the engine you'll see the back of the control valve.
raise the boom and support it, raise the cab, disconnect the linkage at the valve spool. remove the 2 allen bolts from the detent cap.
DO NOT pull on the cap to remove the spool. push it out from the front as far as you can before you start pulling from the rear.
get ahold of the entire cap and spool before you start pulling.

you can find parts breakdowns for your machine @ bobcat.com

Wille has a couple real good threads posted up in this section of the forum on spool seal replacement/ detent assy/disassembly.

 

[mikebramel]

Let's emphasize DO NOT pull LOL!!!

Worst case you can get them back together with the snap on needle nose that have the grooves in them

 

[Al Miles]

Thanks,
When I have the engine shut off I move the pedals and they move freely, when I start the engine, run at operational rpm and move the pedals the lift pedal is sticky. Seems to be pressure related.
I've decided to pull the valve out and reseal the whole thing.
That leads to more questions.
My manual says there is two valves a Gresen and a Melroe. How do I tell which one I have?
The manual also has the instructions to disassemble and and reassemble the Gresen valve only. It any Idea where I can get instructions on the Melroe valve?
The manual also says to undo all the lines and remove the valve from the machine, I can't see how it would come out with the engine and all the other stuff in the way. Can it slide out without removing a bunch of parts?

 

[Al Miles]

I took out the engine, muffler, rad and oil cooler. I pumped out the oil tank first.
When I removed the top [lift] spool the cap on the back was broken. The tab on the bottom and some of the surrounding cap was separated. That may be the cause of the jerky motion. I did push the spools out from the front but the springs on the top and bottom spools are held on with a snap ring and the center two looks like they are bolted on.
The parts book shows three different kind of seals so I imagine there is three different types of spools as well.
I hope the caps are still available.

 

[Al Miles]

Took forever to get the seals from Bobcat. 10 quad seals and the cover, the ear was broken off mine, $410. I thought he was joking and almost fell over when he wasn't.
Cleaned up things this morning to prepare to replace the spools. Now I know what you meant by not pulling on the detent cap. I pulled the cap off and sproing, a spring and two balls went flying somewhere in the garage, no way in a hundred years I'll find those. Now I'll have to order new, I wonder how many hundreds that will cost.
I had no Idea they where even in there. I should have found a drawing if this stuff first.
Live and learn.

 

[mikebramel]

You just need a few ball bearings the right size. Maybe 1/8"

 

[Al Miles]

Close, a 3/16 drill slides right in.If I could find some small ball bearings I'd be good to go. I found the spring laying on the lid of a package of deck screws 20 feet from the bench. Searched the garage for an hour but couldn't find the steel shot.
Hmm I wonder if I have any steel shot from a 12 gauge that would work.