Good morning all, I have an '81 which has been a great bike. But when it gets warmed up, it stalls out after a few minutes. When it cools down it'll start up and run fine until it warms up again. Any ideas?? It's got new plugs and gas. This all started during the first ride of the year.

When you say cool down, how long are we talking?

have you done a tuneup? drained the crank case breather

Have you checked the fuel flow to the carbs? The valve may be partly plugged and you are getting limited fuel flow. Just enough to get to warm-up.
Garth A.

It could be the vent in the fuel cap. If that gets blocked then fuel will stop being delivered as the vacuum builds up in the tank. When it's left for a while the pressure will be slowly restored allowing fuel to flow again.

Try loosening the fuel cap and see if it still stalls.