Get the points checked and make sure you're getting spark out of that new "parkplug" lol.
To test this, take the plug OUT of the head, plug it into the plug wire and hold the threaded end of the plug against the fins of the head... do not bridge the gap between the point and the conductor or else it wont work... Then, crank the motor to see if your plug is sparking.
A bright purple/blue spark is what you should be seeing... If it's dull/dim your points may be failing. In this case you will need to remove the timing cover, and check the gap and condition of the points. These are located inbetween the spinning flywheel and the stationary coils. if there is a lot of corrosion, use a fine grit sandpaper to shine the surface of the flywheel. This will give you better conductivity.
if this does nothing for the spark.. you may need new points all together....
NEXT: if you ARE getting good spark, look at the plug and see if it's wet or dry. If it's dry try squirting some fuel into the head combustion chamber via the spark-plug hole, throw the plug in and crank it... if you get combustion then you have a fuel problem... check your float and the ports in your carb, then check the fuel lines for any kinks or cloggs.
If your plug is WET blow it off, turn the fuel off on the petcock and try cranking it over again. Your carburator may be flooding the cylinder due to a faulty float or some other reason.
between each trial/error start be sure to click the choke on, use half throttle, crank it twice, open the choke and crank it again with no throttle... this way you've got a constant to base how it starts... this is to be sure no human error is involved.
If you try all this and nothing seems to work, bring it to your local small-motor/scooter shop, they should be able to diagnose the problem quickly.
Sorry if this doesnt help :-/