Do some more investigation on the glow plug system. The glow plug timer on a 743 is the person with their hand on the key, you should be able to hear a solenoid click when you turn the key to the left to activate plugs. The aluminum "wires" between the plugs get a black corrosion built up on them at the connection, wire brush works good. Ohm the plugs while the wires are off, there is a value but I cant remember. All should be close to the same however. White smoke and no start means it's trying to burn the fuel but it just not warm enough to light off.
All that being said I've saw many 743's that would not start on a 100 degree day without glow plugs. Kubotas are very sensitive about ether, just a whiff is often too much and will lock it up. Absolutely do not use ether and glow plugs together !!!