Try replacing your current 2 stroke oil with 100 percent synthetic 2 stroke oil. Available at any motorsports dealer. Worked for my Razz. Has not smoked since.
There are several reasons why a Yamaha Razz may quit running. These include issues with the engine, its age, issues with spark plugs, lack of gravity, lack of oil, lack of gas, etc.
If gas is leaking from a Yamaha Razz muffler, then the float may not be set correctly. This means that it is not shutting the intake off.
Here's a link for the Razz repair manual-http://www.mediafire.com/?xibwfty2mtj
Yamaha Razz Service Manual (found through Google and another WikiAnswer question) http://www.mediafire.com/?xibwfty2mtj Also available at http://scootertime.net .
.039-.043
It holds 700 cc of 10w-30 motorcycle oil ( or .7 litres ). I know this because I just got done replacing my clutch and drive chain.
650ml
yamalube 20w30
Wee wee
http://www.scootertime.net/viewtopic.php?f=39&t=954
Synthetic lube