Lonny,
The aluminum clutch is your culprit. Aluminum disks work great for pulling competition; but, have some drawbacks when used for less demanding applications. Aluminum on steel has a very high coefficient of friction resulting in a extremely strong clutch; but, you can't hardly slip them when the tractor is not heavily loaded. They tend to be either engaged or disengaged with no middle ground. There are some things you can do to lessen the problem.
Disassemble the clutch and replace the teaser spring with a 5/8 " ID by 1/2" long spacer. Then put a 5/8" split lock washer between the pressure plates. The lock washer will serve as a spring to force pressure plates apart when you start to disengage the clutch. Doing this will give you a much smoother clutch action with the aluminum disk; but, it will still be harder to slip than a stock disk. It will get a little smoother once you get a little wear on the pressure plates as well. If the pressure plates have just been resurfaced, they have a relatively rough surface which compounds the problem your having.
The aluminum clutch is your culprit. Aluminum disks work great for pulling competition; but, have some drawbacks when used for less demanding applications. Aluminum on steel has a very high coefficient of friction resulting in a extremely strong clutch; but, you can't hardly slip them when the tractor is not heavily loaded. They tend to be either engaged or disengaged with no middle ground. There are some things you can do to lessen the problem.
Disassemble the clutch and replace the teaser spring with a 5/8 " ID by 1/2" long spacer. Then put a 5/8" split lock washer between the pressure plates. The lock washer will serve as a spring to force pressure plates apart when you start to disengage the clutch. Doing this will give you a much smoother clutch action with the aluminum disk; but, it will still be harder to slip than a stock disk. It will get a little smoother once you get a little wear on the pressure plates as well. If the pressure plates have just been resurfaced, they have a relatively rough surface which compounds the problem your having.