Are you saying the engine BOGS down? Or that the tractor just does not have the power to do work that it used to? How's the general maintenance been, Hydraulic system purged, engine tuned up, engine timing set, air filter replaced, Possible new carb, if throttle shafts are worn, etc
The Hydraulic system in Case tractors uses MOTOR OIL because of the hydraulic motor in them, 15W-40 is generally recommended. Doing a total purge of the oil on a loader tractor can get involved because of the oil in all of the cylinders. https://casecoltingersoll.com/showth...l-Change-648BH
Also while the tractor is running take a look into the Reserve tank and see if the oil is clear or if there are bubbles in it. If there are bubbles in the oil the pump is sucking air and unless you find a bad suction line on the tractor, the pump is shot and needs to be replaced. https://casecoltingersoll.com/showth...ne-leaking-air
Let us know what you find.. I've torn my 1973 646a almost to the frame and replaced or rebuilt LOTS of it, so many of us have been there.
1973 Case 646 (w/Custom Power Steering)
1968 Case 155
1958 JI Case 310 Terratrac Crawler Loader
So new to me tractor, newer hydraulic pump and oil from previous owner. My issue is I here all the stories on what people are doing with there tractor and mine I cant move dirt or lift very much because my engine bogs down and just about stalls out
New OIL? do you know what type of oil they put into it?
New pump? If the pump is OVER sized for that 14 HP engine, its going to bog it down when the pressure climbs.
Old Kohlers often wear down the push rod for the points, which makes the engine timing changes. On the 10 HP Kohler in my '68 Case 155, I had to modify the points mounting to be able to adjust the .020 opening. I need to get into the engine some day and replace the push rod. Good information and replacement Kohler parts on Brian Millers Web site: Ignition Solutions for Older Small Engines and Garden Pulling Tractors
If seems to be Engine then you have somewhere to focus first.
All engines need air, fuel and Timing to work. And in the right ratios.. If the carb is old and worn it can suck air in past the throttle shafts and lean out the fuel. If the Carb flanges and gasket are not flat, it can leak air there too. If the air filter is clogged then you might not get enough air.
If the push rod for the points is worn, the timing could be off. Valve lash probably needs adjustment.
I know on the Onan Twin cylinder engines we do a regular "decarbon" of the engine, which is pull the heads, clean - scrape all of the carbon off the piston, valves, heads, etc and check valve lash, new gaskets re-assemble.. Might be a place to start on that Koher as well.