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Discussion Starter · #1 ·
Hi, I am new to the forum, so your patience is appreciated as I learn how to navigate around the site.

I recently purchased a MTD 142 995, circa 1980 or 81, based on the date code of the 18HP briggs twin. When I purchased the tractor, mower deck, and large snowthrower, there were no attachements mounted. Hyd lift seemed to work when tested with no load, a little slow, but worked.
After correctly mounting the deck, it is apparant there are hyd lift issues. It lifts slow or not at all with the deck attached. The lift valve uses the same hydraulics as the drive hydrostatic (correct me if I'm wrong please) and the hydro drive works perfect. Owners manual decribes fix for slow lift, which I tried by removing acorn nut on lift valve and turning in set screw. I was so excited there was an adjustment for my problem, however, adjusting the set screw over and over did not improve things. Crap, now what do I do? Thanks, Larry
 

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Discussion Starter · #3 ·
Thanks H-D. I should have mentioned that I did change the fluid and filter also. I did so since the cost was not too bad, even though the fluid looked clean before I changed it.

Larry
 

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Discussion Starter · #4 ·
Another thing I could mention here. Through trial and error, and mowing with this MTD the last week or two, the hyd lift works pretty good with cold engine, cold fluids, at start up. The deck will lift up in about 10 seconds, which of course is way too slow, when all is cold, but after a few minutes, when things are warmed up, forget it, not much action on the lift.
 

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Sounds like the pump is tired.
 

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Have you seen the video on a Hydro pump which a member DTLMG linked on here? They work on the same scheme as variable displacement A-C compressors & the one in his video had 2 of the 5 pistons stuck in the cylinder block (pretty fair reduction in volume). The complaint on that tractor was "slow, jerky operation when hot". It might be worth a look; the price is definitely right!
 

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The pump that operates the hydraulic cylinder is the "charge pump", not the variable displacement/hydrostatic pump itself, really. The charge pump is a roller pump attached to the front of the hydrostatic pump; its purpose is to feed oil to the hydrostat, but obviously it generates excess flow which can be used to feed auxiliary circuits. You noted that your hydrostat seems to be working well, and given that these charge pumps are pretty reliable, I would not suspect an issue there.

First, check to make sure the control handle for the valve is giving you the full range of motion for the valve spool. I know on mine, and others have reported it as well, the link between the handle and valve spool is not very solid. Similarly you would want to check to make sure that no other physical connections are broken and that the hydraulic cylinder would be able to operate the rocker arms properly.

The next test I would suggest would be to try to move the hydraulic cylinder when the tractor is shut off. If you get movement from the deck/rocker arms (make sure you give yourself good leverage) then you have a leaky valve that would need to be rebuilt. Regardless of the state of the cylinder, you should not be able to move it if the valve is in neutral position if the valve is not leaking.

If you get no movement from the cylinder with the valve in neutral position, then the cause would be the cylinder itself, leaking oil around the piston.
 
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