Help needed with 1200 rock
lucky phil 09-24-2010
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We have a 1990 model 1200 rock that has started pumping faster on the left hand stroke than the right! Any ideas would be greatly appreciated! 
"MUDDY" 09-24-2010
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sounds like the early stages of "mps syndrome" weak spring in the MPS spool.
lucky phil 09-24-2010
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Thanks muddy ill check that out! had a play around with it and it gets better the softer the change is set on the rock!
b-alto 09-24-2010
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On a 1990 they didn't stroke all the way open and you would get wear on the cutting ring, which causes grout loss and extra pressure on the bad side. Maybe thats it? On mine it was, seemed like one side was stronger.
Many 09-24-2010
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My memory is real bad but seem to remember a check valve on diff's.

http://schwingaustralia.ihub.com.au/
"MUDDY" 09-24-2010
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you are right Many. Big long ones on each side.
pump031 09-24-2010
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1990. I dont think the mps was around then,  I would bet that is a non-accumlator system with a screw in dial(black looks like a stroke limiter) up by the brain.  I would look at diff like the other posts
gboom 09-24-2010
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when you are pumping, is the cp hyd. pressure the same on both cylinders? are your diffs still in time? you may have a cylinder that is leaking internally and you can tell by the delay at the end of the stroke

"MUDDY" 09-25-2010
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I think you are correct PUMP031. Wasn't paying attention to the year model. They call that a dampener on a non-accumulator system. It is the same type valve as the stroke limiter.
90624 09-25-2010
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Check nozzles in the dampner vailve and fast switch, might be plugged.

 
30something 09-28-2010
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90624 is probably correct, the return orfice in the fast switch system is partially plugged and not letting the reversing valve return after each stroke.  Try cleaning out the orfice if that solves the problem but comes back again try drilling out the orfice to 1mm.
Phill 09-29-2010
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Hi Lucky Phil

This is Phil Serre (Ex Schwing director of training)

My guess is you have a leaky switching valve causing fast switch to stay on to long (keeps feeding oil to .7 mm orifice) -- thus the reason for only one side.  If it was the orfice pluged it should do it on both strokes.

I am in Australia this week (remember that when you try to call) but you can call me and I will explain how to figure which one is bad -- "The diff test"

Phil Serre

Serre Consulting  612-840-9211     or (651-257-3773)