not actually a scooter
Anywho..
"great effort to get going"...
what do you mean by that high resistance on the pedal,
or low resistance on the pedals but no combustion happening?
the latter I assume, since that'd match my assumption and could be the exact same cause for it dying at any somewhat open throttle.
So do me a favour and try this:
clean the spark plug as good as you can (ideally get a new one in)
then start it up (I know.. please once more!)
then rev it up as high as you can (gently... do not rip that throttle but caress it to the highest rpm you can get to)
as soon as it died, remove the spark plug and take a pic of it to show us.
I'd expect it to be wet (dripping wet even)
My thinking is.. since that thing now has ~30 years of abuse on it's saddle and likely little to no maintenance,
the piston rings or even the cylinder walls are completely worn out..
causing a severe lack of compression and thus making it terribly hard to start..
Since as it got harder and harder the inexperienced rider might think adding fuel can solve that..
now with no noteworthy compression all that uel is just spoiling the spark plug making it even harder to start.
Solution: rehoning the cylinder wall and fitting oversized pistonrings (or piston where due)
don't worry.. it sounds worse than it actually is.. a honing kit costs a few bucks true (50-70ish) and while psitonrings aren't expensive, sometimes pistons can be (IDK about the Tomos.. but I'd say it might be again in the 30ies dollarwise for a new piston)
Chances are you (well.. your friend) got really lucky and the spark plug ends up one dry.
in which case a carb clean (NO replacement just yet..)
disassemble it, boil in lemon juice, blow every nuck and cranny with shop air and repeat twice until you checked every ever so tiny air passage to be free of debris.
reassemble and it'll be as good as new and you havent spend more than a few pennies for it.
maybe new gaskets.. and the lemon juice that's usually all it takes)
Most airfilters can be cleaned.. some need to be replaced.. I can't tell w/o pics of course.
So *shrugs*
But to me that sounds like a worn out cylinder wall.
While at it, cleaning everything on the engine is a good idea,
and if you have to remove the cylinder it's also good to check the ports
(or does it have a reed valve.. it doesn't, does it?)
if it does.. make sure the valve is still in good shape
(no broken flaps, no crusty fins, and closing properly)
maybe do that BEFORE you remove the cylinder since a broken flap can be the culprit as well
what else?
Oh right: those two strokes need a matching exhaust.. sooo
if someone drilled holes in yours or cut a part off or installed a nice looking four stroke exhaust instead (to get rid of that nasty pineapple shape [which is the needed expansion chamber])
then you should fix that as well..
'sid