Motorcycle Repair: Yamaha Mate Scooter, 2 stroke engines, oil injection system

Question
Hello,
    I have a Yamaha Mate Scooter (similar to the Yamaha u7). When I bought it it had not been running for 25 years.
When I finally got It cleaned up and started it it did run for about 10 minutes. When I tried to start it again it would not start.I cleaned the carburetor, everying seems open and clean even the needle valve. I have good spark even though it still has the orginal points which I cleaned and set. It is getting fuel to the carburetor. It seems to have good compression. I never had a compression test done but when I put my thumb over the spark plug hole and crank the electric start, it blows my thumb off. It has the vacumm type petcock so the gas only flows when the bike is running. When I blow into the vacuum line I can hear the diaphragm working. I am running out of things to try. If you have any suggestions, let me know. Thanks for your time.
                                         Andrew

Answer
Andrew,

If the spark looks good,
try a good spark plug and
spray some carb cleaner or
wd40 in the back of the carb.
See if it fires, if it does then
you know it is having trouble getting
enough fuel. The carb may need more
cleaning or the reed valves may be stuck
under the cover where the carb goes on.
Some models had a rotary intake valve.
If the carb is on the side it is a rotary
valve engine.
The petcock works with suction only.

After sitting so long the crankshaft
seals may be damaged. If they leak it
cannot pump fuel through the engine.

Are you using 2 stroke oil in the
fuel? I believe these are 2 stroke
engines and need oil in the gas unless
it has an oil injection system (Autolube,Yamalube)
If premixed use 4 ounces oil per gallon of gas.
Without oil it will seize up.

Double check your points and carb, air filter etc.
It might just need some more coaxing.