I have a 1973 90cc G3 (vin # GA 359641). Approx 3500 miles. Appears to have good compression, but I have not put a meter on it. I have had it 15+ years sitting in dry storage shed. Took it out for my son and got it running. Replaced the fuel line and filter. It also needed a (crank?) seal replaced. Would run but smoked when throttled up (discribed to me as sucking oil from tranny into engine during throttle up?). Anyway, bike has run great for approximately 45 min-1 hour. Stops running. Is not seised up, but just like you turned the key switch off. However, the engine has visible spark when plug removed and cranked over with kick start. Lights do not work, I did not get a new battery (wanted to see how it runs before becoming further buried). It acts like no spark-i.e. no coughing nothing when it is kicked over. Fairly sure it is getting gas. Have taken plug out and blown off. Makes no difference still acts like the key switch is turned off. Would the spark plug still show a spark if the key switch failed? Is there a way the timing on these engines can jump or suddenly change? Checked throttle cable and is working. Would a short on the electrical system cause this? My understanding is 2-strokes don't have valves, could it not be getting fuel from the carb to cylinder (2-stroke equilvilant of valves not opening/closing)?