I replaced tine drive belt and the problem remains with my Ardisam 3100 Earthquake front tine rototiller: the clutch will cause the tines to turn, but with virtually now power - just setting them to the ground will stop them from turning...lift them from the ground and they will begin turning again. If clutch is released they will stop.

The clutch cable may need adjusting.

contact the manufacturer on the net and look for a pdf version if available.

Sounds like the belt is slipping. Have you removed the belt cover and inspected the belt and the tensioner pulley ? If your model is like mine the tension can be adjusted just below the handles by looseneing the nut where the cable goes into the cable sheath and moving the cable cover further away from the handle. That takes up some slack and will make the tensioner pulley tighter on the belt. If the belt is shot tension isn't going to help.
Try "google" with "earthquake 5070 manual" first option should be a PDF copy of a model 5070 manual. Will have diagrams on how to adjust the cables.

the tensioner is to tight and belt stays engaged loosen the tension below the handle

Either clutch is bad or teeth are striped in bottom gear box. remove tines run engine and see if you can feel movment in lower gear box, if yes the gears are gone. If no remove engine to expose clutch.

Remove the 4 to 6 screws holding the engine to bottom gear box and lift eng off. clutch is right there. It could be the teeth on the lower branze gear are stripped. lay machine on its side and with tines off remove gear box cover.

I need a service manual for the earthquake 9800 auger with the 3.8 hp tecumseh.

I googled Earthquake 5020DM tiller and show a site that has a technical manual. It has the diagrams and parts numbers. It looks like the forward and reverse cable are the same. You may have to call ARDISAM direct to get the cable.

DID THE BELT SHRED OR what happened if it is still decent mesure width on top is it a v-shape belt or flat & last thing is cut it & measure it if its still decent that will give you the specs or if theres other # on belt & who its made by