Craftsmen LT 3000 will not crank

Remove deck belt from engine pulley, then remove the idler pulley for the drive belt, remove drive belt and reinstall.

Have you tried bypassing the cut off switch, by joining the wires together

oftentimes the things will not start after sitting idle all winter as last year's gasoline has turned into a lacquer which has blocked the flow of fuel through the small passages in the carburetor. there is at least one product, called Stabil, which you dump into the gas tank which precludes this. So maybe a carb rebuild and clean out is in order; and if it then works OK you should make a point to put some of that stuff in your tank at the end of the season. Works well for RVs also.

thay are counter clockwise

For a small gas engine than won't start, think FAST -- Fuel, Air, Spark, Timing. You've replaced the filters and spark plugs and squirted in some starter fluid, eliminating the simple common fuel, air, and spark problems -- but I because of the backfiring I think your problem is in the timing -- like a sticking valve. Probably more than you want to tackle at home, but might not be as expensive as an engine replacement. Take it to a good small engine mechanic -- best bet is a lawn equipment shop that has been around many years. Drive a little farther to get to one if necessary.

remove the starter...use jumper cables to "run the starter manually...red to big lug, black to body (anywhere is fine) should torque hard at initial run and continue to run smooth...if it buzzes or vibrates, it's bad...replace...

First I would suggest making sure your battery is completely charged and is in good working order. Have a "LOAD TEST" done on the battery.
Second check and clean all battery connections

If this does not help then you may have a bad starter drive and need to replace it

adjust the clutch cable

No,You need to park on a level area and lower the deck to it's lowest setting and adjust the deck with the large butterfly nuts on each side,just under the foot pan,just loosen and let the adjusters fall into place,Tighten back up and it should be set.You may need to do this more than once.

* If your yard is up to an acre in size, the ideal cutting width is 30-42" (76-106cm). To avoid being underpowered, or putting too much strain on the engine, make sure your mower or tractor offers a minimum 14 horsepower. Riding mowers are the most commonly purchased for lawns this size. * For a yard that is between one and three acres, you’ll reduce your mowing time with a cutting width of 42-46" (106-116cm) and a strong engine up to 16 HP. Typically people purchase lawn tractors for yards of this size. * If you’re mowing more than three acres, you’ll need to look at the garden tractors, with cutting widths up to 54" (137cm) and at least an 18 HP engine, preferably bigger.