Here's the scenario:
I forgot to bring my moped into the garage last night and it was left out in the humid night air all night. I went out to start it this morning in fog with about a mile visibility and it started and promptly quit without sputtering or misfiring. It would run fine for a few seconds and then quit firing all together. It was all or nothing. I put it in the warm garage, started it and rode it about a qarter mile and it started to quit again. I put it back in the garage and it only runs for a few seconds at a time. I pulled the carb apart, and fuel flowed freely throughout the whole thing. I pulled the spark plug and checked the spark, and it is bright enough to see under fluorescent lights.
Here's the stats:
1977 Puch Newport (same as a Maxi)
2hp engine
over 6000 miles
Just took a 20 mile trip two days before, no problem
50:1 oil mix, 2 stroke snowmobile oil (it was all the gas station had)
inline fuel filter, flows fine
30 to 40 degrees F outside
Biturbo Exhaust