Rough Idle and running after a long hard trip.

[slythern12]

My 97 standard normally runs really good, but after a long hard trip going 75 to 85 down the interstate for a few hours she runs rough and sputters at take off. The next day she is fine, any suggestions.

[BonS]

Well, I like playing guessing games! Heat-soak comes to mind. There's a plastic heat shield behind the radiator and just ahead of the carbs that's there to deflect heat away from the carbs. Any chance that it's missing? Of course, the ignition coils and ignition module get hot as well. I've not heard of them failing much if at all here on the board though.

[Michvalk]

Vacuum to the petcock. Probably have a leak in the vacuum line or a diaphragm in the petcock going bad, causing slow or low fuel supply

[slythern12]

Wouldn't it be a constant problem if it was a vacuum line to the petcock? I rode down to Hot Springs Ar from Fayetteville Ar about a 200 mile ride taking Hwy 71 kinda curvy rd so going 45 to 65 the whole way no problems at all. On the way home I take the interstate going 75 to 85 almost all the time and when I get to Fayetteville she is sputtering all over the place. Same thing when I went to OKC a couple of months back interstate there and back. But she is fine the next day and so far fine as long as im not doing interstate at hi speeds.

[The emperor has no clothes]

Maybe a cover set rebuild is needed. Might not be getting full flow . It's easy enough to take apart and inspect. Or possibly an old fuel line that is getting kinked as it gets hot.

[Gryphon Rider]

If it were a fuel flow problem from venting or a tear in the vacuum diaphragm of the petcock, the bike should idle okay, especially after being off for a few minutes, but bog down when more fuel is required, like at highway speeds.  This seems to be the opposite of what slythern12 is experiencing.