First of all, are you doing a compression test while fuel is entering the engine as per normal ?
If no fuel is getting through you WILL get false readings and the bores could get scratched/scored.
Have you tried something like powertune or deep creep to free up any gum in the piston rings ?
Do make sure your using good clean fresh fuel and that you have good plugs of correct gap and type.
It sounds like your carbs need a proper clean, use good carb cleaner and compressed air.
Take every single thing out of the carb possible, and see if their are any plugs that can be removed to gain even more access to the cavities and voids of the carbs.
if removing any jets or air screws, make a note of how many turns etc on each carb jet, and keep the same jets/screws for each carb seperate while cleaning.
Now I dont know where people like racer one are getting their info about running dry of fuel being ok for the internals.
Just look at how the engine works, and what lubricant is used.
Now first of when an engine is just on the point of running dry it will speed up a bit as its running leaner than normal.
With a 2 stroke the entire crank area will be scavenged of the fuel oil mix by the final few up strokes of the piston ny
means of pure suction.
The fuel oil mix does not seperate in the combustion are or in the crank are of the engine, it stays a mixed fuel /lubricant.
This is exactly what 2 stroke oil is meant to do, its not meant to leave anything behind, it stays with the petrol all the way from carb to fire/exhaust, if it dont then its not doing what is says on the tin.
I have had a few of my very own engines rust up due to not lubricating the internals after running dry.
2 stroke oil fuel mix is not now or ever been a good rust preventative and was never meant to be.
The whole idea of fogging oil and winter lubricant is exactly what is needed to stop corrosion of the internals.
ANY Good engine technician who has a good idea about fuels will also tell you the same.
Petrol and 2 stroke mix when used in a 2 stroke engine and running the engine completely dry untill it stops,is starving the big ends, small ends,wrist pin, and crankshaft journals of their fuel oil mix (lubricant). The internals will form rust over a short period of say 3 months as the slightest micoscopic drop of fuel oil mix will evaporate leqaving the internals to the moisture thats left.
Now at this very moment im doing some work on 2 v8 detroit diesels of 760hp each, the fuel has diesel bug ,although a different subject, it again causes contamination and rust on every surface due to amount of water in fuel.
water in fuel is also very common in petrol nowdays, and again if you let even a diesel pump run dry you risk corrosion and rust.
Inhibitors are used by any good marine engineer over the winter period to try and stop any corrosion.
The very same type of inhibitors are used in petrol 2 strokes.
Its not rocket science, just plain sense that the fuel oil mix will not lubricate if its not there.
Now also on the 2 stroke engines, i also race small radio control boats, i can show you results of engines run dry of fuel.
completely rusted to pont of so corroded they break up the crankshaft.
Do yourself and your engines a very big favour and use a good oil for after run, it will save a fortune in the long run and keep the engine internals lubricated when stored up for winter or long periods.
phill