Here are some of my personal thoughts on the 2 stroke Detroits. If it won't start without ether within a 15 second crank cycle at 35 degrees, the compression is down a bit from wear, or misadjustments to the fuel rack, overhead, timing, governor, or fuel pump delivery pressure should be/need evaluated. Each engine is different so not assuming rings, valves, or anything really as they are all tended to with a "freshening up".
Most of the two strokes take to ether like a duck to water but it's easy to overdo it without a "measured shot" system installed. The unfortunate part is many engines, (all series and types) have met an early demise because many tend to overdo it with the spray. Just a quick shot is all that's needed but I've lost count of the times I've seen a steady stream being applied till the engine fires off and the subsequent preignition resultant that shortens lifespans. I've had several apart with busted rings, mashed ring lands, severe burning to piston crowns etc. from the overuse of ether.
I've not been around a lot of the "53" series myself but those I have been around have been maintained well and start very easily.
