Complete shutdown in cold weather

[WEDTWIKE]

1985 Honda ATC 250es. No problem cold starting. 20 degree weather. Ride for about 15min +/- and then it completely shuts down. No dying down like it's out of fuel but skids to a stop. Fuel is fresh. I try to restart it but it seems hard to turn over. After a few minutes of cooling down she slowly starts up, I get her and I park it. This has happened the 2 times I started it this winter. I don't know the grade of oil originally used but I got it from up north and would expect the oil to be 10W30. Any thoughts? This is my first post. Great site.

[Flyingw]

When that happens, pop the gas cap off and see if it starts up right away. Listen for a sucking sound when you pop the cap.

[WEDTWIKE]

Took her out today. Rode for about 30 min. No problems. Pulled the gas cap. No sounds. I keep the tank vent open always. I'll ride it more this evening when it's colder and see what happens. Thanks for the response.