Custom Bobber with 1340 EVO - S&S carb .. Riding recently the bike began to run at half power. Moments later the bike regained full power and was fine for a short while. Before I got home the bike did the same thing again. By them time I was home it ran fine! ANY IDEA ?

 

Coil, plug wire, plug. After that, it gets mechanical.

 

Plugged vent on tank or carb would be another place to look.