Been having this problem intermittently for about a week, let me know if you have any ideas.

So, I start up the bike, allow it to warm up abit, then go for a good 20-30 miles ride. During the ride the bike will run fine and idle and rev up like normal. Then after about 15-20 minutes of riding or sooner after some enthusiastic riding, the bike sounds like it hiccups and then sputters then idles and runs fine. If I continue to ride the bike hard the bike will usually hiccup again at the next stop and then sputter and die. So far I have been able to start the bike right up and ride back home to try and figure out what happened.

My bike is an '87 750 Paso, running flatslide SUDCO mikuni's with KN filters, and Cobra F1 exhaust. No other changes to the bike that I know about.

Sounds electrical as in a loose connection. I have found the round connector at the bottom of the Ignition most often to be my problem
Flag terminals have always been troublesome,the terminations are cheap but the proper tool to crimp them will set you back a couple of hundred dollars if you don't have access to a well tooled tech. It of course can be a loose terminal anywhere on the bike or internal to the switch. The 750 faq has a detailed listing on how to fix your switch. In the end you need to check all the wiring to nail down the problem. Get stocked up with your beverage of choice,put on some tunes and spend a day going over every wire,connection and especially those grounds. Intermittent problems take time and patience to track down and stomp their troublesome Gremlin like ways

The relay mods you can find here will also go a long way in chasing away the gremlins, VooDoo incantations never hurt as well as learning to curse in Italian Very gratifying.. I have heard our Kiwi and Aussie brothers have especially fine tuned the art of incantations and especially powerful curses Then there are the very special,known to stop asteroids in their tracks Finnish curses Be very careful, they can be hazardous to innocent bystanders and young children

Yeah, I'm going to go with an electrical connection also. Maybe a ground. Check the mounting bolts on your coils.

Clean every terminal and connector, and put some dielectric grease on them before putting them back together. If possible, use two needle nose pliers to take connections apart. This ensures that you don't break the wire by pulling it apart, but also give you better tactile feedback about the general health of the connector. You can feel if the connector is good and crisp, or if it just slides apart with little effort. You can then tweak the connector to get them nice and crisp again.

I agree on the Relay mods, and also adding a bigger, or second ground cable from the battery.

Cheers,

In addition:

Check fuel filter. Whe was it last changed? Are the hoses kinked/crimped?

Tank vent? Does it make a slight sucking sound when you open the gas cap after it stalls? Kinked vent hose? blocked vent hose?