Yanmar YM2500 3pt Photos and Description

[chriswheeler]

This thread goes back lots of years. ( almost 7 ) After all of this time, still havn't ever been able to get my draft control to work right on my YM 3000. I'll go back and check the keys and set screws on lever #5 and see if all is in order. I know it does have draft control, just has never worked right. I also have a JD 950 that does not have all of that, can definately see the difference. When I'm done rebuilding the 950, will go back and have another look at the YM 3000 and see if I can get this thing to work,
Chris

 

[California]

With a heavy implement, there is also a valve that should bypass the fluid pressure with a hard jolt, if this is not working, it can create higher than normal pressure in the system, (the feedback can't react quickly enough)....

If you have a very heavy implement and you are bumping around a lot, I would lock the hydraulics with the knob under the seat to bypass the feedback mechanism to reduce the strain on the pump and bypass valve, just don't forget to open it again. ...

any corrections or further info is welcome.

I'm not sure it is a good idea to tighten the knob under the front of the seat when carrying a too-heavy implement, since that chokes off the passage to the relief valve. Seems to me if the fluid can't escape then this would blow out a seal (or break mechanical parts) in case of a severe jolt.

I've been tempted to close that valve. Driving around with the backhoe on, I can hear the relief valve squeal when I drive over a bump. But I think it is better to not close that valve.

 

[careyo63]

I believe the Oper. Manuel calls it a Serv. Stop Valve. I would tend to believe it's hard to Serv. it while your using it.

 

[neflfarmer]

I just checked the service manual. It's description of the stop valve is- " the stop valave allows the rockshaft to be locked out of the hydraulic system or lock the rockshaft in a raised position". In looking at the diagram it does just that. The fluid in the rockshaft piston is "trapped", and no circulation is possible. This also eliminates the relief vlave, as stated, if a heavy weight tries to push the rockshaft arms down, (since no pressure is on the valves or pump).
The only pressure is then on the rockshaft piston, but I don't think that would be much higher than the pressure if you put the same load on the arms with the lock off when the feedback arm applies pressure to keep it at the level set. So it could possibly put more pressure on the piston O-ring seal, but if that were to leak or pop, it was probably weak anyway, (and better that than the pump working too hard, oil temp going too high, or the relief valve failing). And the O-ring is captive in the middle of the piston, so very secure.
To test the relief valve the book says to close the stop valve and then move the control lever rearward and check the pressure. In this case you are eliminating the rockshaft and making sure the reilef bypass is "bypassing".
IMHO, you can use the stop valve to lock the rockshaft, just try to make sure the control lever is set forward after locking so you are not pumping oil through the relief valve and causing it to get hot, (short periods are fine). If you accidentally pull the control back, all that should happen is the oil will flow through the relief valve and eventually get hot, but the rockshaft should stay put.

California's point I think is valid though. Something like a backhoe is a very heavy implement, with a long "moment arm" that could apply a lot of pressure. I think more in terms of a box blade, mower or scraper, since those are what I use.

One more caveat, if the feedback linkage is not adjusted properly, and you screw down the lock, it could be actuating the control valve and pump through the relief constantly, that's easy to tell though, if the lock is on, you should not hear the telltale "squeal' of the bypass working. Main thing is that when locked, the hydraulic system should not be doing any work, and the arms should be rock steady.

 

[neflfarmer]

I just had a thought. I'm going to start a thread and ask if anyone has used the stop valve in operation and see if anyone had any bad experinces. Great discussion in any case. There is a lot to learn about these things! I'm just glad I can set my 3pt where I want and it stays, stop knob or not!

 

[careyo63]

Had it Happen on a New fredricks YM2500. Yep! Operator error. Just using a 6'BH. The stop valve was closed and it started POURING Hyd. fluid were the Lines connect to the pump. Snuugged the O-Rings back up and it stopped to a small drip every now and then.

 

[neflfarmer]

Careyo63, thanks for the info. When you say operator error, can you expand on that? Just wondering if you were trying to lower/raise the BH, or just left the lock on and bounced around? I am trying to determine if you can use the stop valve as long as you don't try to move the control lever. "IF" I understand how it works properly, if the lock is on, as long as you don't move the control, the pump/bypass/etc should not get any stress as it should be isolated. This assumes everything is working as it should of course.
And it sounds like after tightening up the seals, you still used the lock? Or no?
Thanks.

 

[careyo63]

Careyo63, thanks for the info. When you say operator error, can you expand on that?
Someone turned the Ser. stop on and left it on.

Just wondering if you were trying to lower/raise the BH, or just left the lock on and bounced around?
I believe they were Thats IMO.

I am trying to determine if you can use the stop valve as long as you don't try to move the control lever. "IF" I understand how it works properly, if the lock is on, as long as you don't move the control, the pump/bypass/etc should not get any stress as it should be isolated. This assumes everything is working as it should of course.

On this Ym2500 It was Pouring Hyd,oil only when it was running so there is Pressure at the Pump. And california just made a statement when useing his Engaged with a load you could hear the pump wine when you hit a bump.

And it sounds like after tightening up the seals, you still used the lock? Or no?

No! Plus if any attachment I Serv. Hooked up I feel safer with the Jack Stands.