As a rule of thumb, it's probably a sticky exhaust valve. Remove the inspection plate w/ the dipstick, reach in & push the control rod to the rear. If the lift drops, you found the problem.
This is a classic symptom of a dirty pump.
Have you ever cleaned out the pump sump & changed the fluid? Check out tips 3 & 4 below.
There are two ways to clean the pump; the quick way that gets most of the crud out of it, & the right way that gets all of it.
For the quick clean, after you get the old fluid drained out (overnight is best) remove both inspection plates & start pulling the sludge in the pump base out by hand. Then, get a couple of gallons of kerosene or diesel fuel & pour it into the pump base. Catch it in a bucket & reuse it. (Some folks use a hand garden sprayer.) Flush the pump base out 5 or 6 times. Do not start the engine to run the kerosene through the pump; kerosene and diesel fuel do not have any lubrication properties & you will damage your pump.
Some folks will tell you that this 'quick-clean' is not as effective as dropping the pump & doing a full job. I do not dispute that, but it worked for me for 3 years on my 1951 N. If you have the time, drop the pump; that is the right way to do it.
Do not attempt to do this w/o the I&T FO4 manual; the pump has a bunch of little parts that will go back together wrong if you do not have the manual to go by.
With all of the fluid drained out, block the front wheels & get the rear wheels up at least a foot. (you'll see why soon enough) Remove the 4 bolts holding the PTO shaft in & pull it to the rear & out of the tractor. Remove the inspection plates & reach in & disconnect the the fork from the control valve. Put a block under the pump & a jack or more blocks to hold it in place, then loosen all of the bolts. Remove all but the 4 corner bolts. Then, carefully remove them. If you are lucky, the pump will now rest on the block. If not, wrestle it free. The pump has 'ears' that fit into the housing; wiggle it a bit & it will drop free. If you have the rear tires a foot or more off of the ground, you will have enough arm room to hold the pump & lower it at the same time. Once you get it out & on the bench, it comes apart easily & can be cleaned piece by piece. Putting it back is harder than pulling it out because you have a gasket to worry about. (no sealer on the gasket)
While you have the PTO shaft out, it would be a good time to replace the seal on it. It's got two spring clamps around it. Take your needle nose pliers & remove the one in the front. Then, hang the shaft & bearing housing in your vice & tap the butt end of the shaft; the bearing cap will come off (and the shaft will land on your foot). Then, remove the other spring clip from the other side of the seal. At this point, remember that you never bought a seal driver & go get a BF socket & drive the seal out. If you have the new style seal, the white side goes out. Put some grease on it.
50 Tips
