Hey guys, I really need some insight with this one...
it's been driving me crazy for the last year... this is generally how it goes:

1) Hop on bike and run 50 miles at highway speeds (no problems)
2) Stop for lunch for an hour
3) Gas up and get back on the road (no problems)
4) Within 5 minutes hit highway speeds of 80mph (no problems)
5) Cruising at 80+ for a few minutes and bike begins to miss and sputter (it will eventually stall if I keeping throttling it).

6) So I back off the throttle and coast for a second...
7) she'll usually release a nice backfire like she couldn't breath (I have a Supertrapp exhaust)...
8) then I do a LOT of systematic on/off twisting to keep it running in the 70+ range (kinda like burping a baby)...
9) she sounds like she's gonna choke and die the whole time... rev/cough/sputter

10) Here's the thing... I do that for 5-10 minutes... then it clears itself out and the bike begins running solid again.

This happens like clockwork if we do highway runs...
in the city, I don't ever have this problem.

Carbs aren't my strong suit... but I can't help get this mental image that there's some gunk blocking the top-end needle...
gunk that gets floaty after the first highway stretch... then settles during lunch... and clogs during the next top-end highway stretch.

I don't mind yanking the carb out (though I'd prefer not too right now)...
but I'd like to hear some ideas on what this could be?

If it is just gunk (bike has 26,000 miles from the last 2 years riding),
is there a fuel additive I can try first?

I need to fix this, it holds everyone up (and freaks them out),
every time we ride out of the city. :/

Thanks guys, any insight is appreciated!!

Jay

You are probably running out of fuel. Do you still have the stock vacuum operated fuel petcock? Running at 80mph is a low-vacuum condition. I had a similar problem. At 65mph and a stiff headwind, my Savage would start running poorly, then just quit. The same symptoms as running out of gas. If I switched the petcock to prime, fuel would begin flowing again and the engine would pick up before I could roll to a stop.

In my case, the vacuum petcock didn't leak, it did the opposite. The diaphram got stiff and needed a lot of engine vacuum to flow fuel. Under low vacuum engine conditions, the petcock couldn't pass enough fuel to keep the float bowl filled.

Solution: Get a Raptor petcock.

Had the same problem with my '02, put a Raptor in it and haven't looked back since. Stage 1 cam and new jetting, looking for the ton.

Classic petcock issues... don't buy the cheap one online.

First and easiest thing to try....is switch the stock petcock to Prime and see what happens.

Out of curiosity, how much oil are you burning at a constant 80 mph?

blackhalo, I'm like you about messing with my bike unless it's broke, but the Raptor is a 15 minute fix after you drain the tank. Raptor petcock is Yamaha part number 5LP24500-01-00. I didn't even remove my tank to swap it out. Just bag the old petcock and vacuum hose if you want to keep original parts. Be sure to plug or cap vacuum tube sticking out of right side of carb. And you really do need to check your cam chain from 15-20,000. Mine was just getting ready to drop the adjuster at 20,000. Good luck. Boofer