Sometimes I think it would be better if they made these filters out of black plastic and then you wouldn't worry about the fuel level.
They all run half empty (or half full) sir!
I guess if you mounted the filter vertically, it would stay "full".
In our autumn/winter climate now, I'd not be expecting any vaporisation being the cause of poor re-starts.
At this time of year it's carb icing that can be a problem.
With this, the engine starts and runs OK for about 5 to 1o minutes - then the engine stalls - usually while waiting at a junction or lights.
A re-start can take quite a few attempts
There after for the rest of the day the engine runs fine - because of the residual heat retained under the bonnet.
Engine stopping after 10 minutes of so is classic coil failure. When the coil get hot it shorts out. When it cools back down it works fine
You need to eliminate this possibility - before wasting time and money on other parts.
Simply swap coils and see what happens.
The condenser in the dizzy failing can also cause poor running and re-starts.
Electronic ignition eliminates this problem as you do away with the condenser.
It is imperative that the braided earthing wire under the dizzy base plate is in pristine condition.
After 50 years they get a bit unreliable.