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.
I asked this question before I signed in
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.
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.
2 places
Here's a link for the Razz repair manual-http://www.mediafire.com/?xibwfty2mtj
You have to lift the seat, remove the back rack and taillight assembly, unscrew and remove (just pull, its held in by little plastic clips) the bottom moulding, and lift up the body panel. You may have to push the rubber gas tank cover out of the way. Then, on the side opposite of the kick start, the spark plug is located under a rubber boot within the body panel. The spark plug size is 13/16". You will need a deep socket.
Yamaha Razz Service Manual (found through Google and another WikiAnswer question) http://www.mediafire.com/?xibwfty2mtj Also available at http://scootertime.net .
http://www.scootertime.net/viewtopic.php?f=39&t=954
Bad needle/seat valve on carb.?
Does it run on choke? Is it starving for fuel, if so is the needle valve set for the float?
10th digit of VIN is always model year; use common sense to determine decade.