so when get on the highway it runs great shifting through the gears getting up to 70mph,the when I stop accelerating tomaintain speed it starts sputtering and losing power.
I have cleaned the carb,checked the sliders (not sticking or wearing from sticking), changed the fuel filter,ran sea foam threw it,changed the plugs, checked the card gaskets and seals, in that order and I still get the sputtering at highway speed. Anyone got any ideas? thanks in advance kcgonzo

is it cold where u are at the moment ? could be carb freez?

mines is the same when it cold .

it does it cold or warm

no sure ill have a think ??

Not super familiar with the bike, but I had a similar problem on a Suzuki I had. I would only run smooth when accelerating.

The problem wound up being air leaking in where the carb mounted to the rubber boot. Check the boot for cracks and make sure the clamps are secure.

kcgonzo,

Is the motor stock? Does it have the stock ignition module?

air filter ??

it has a hyper charger on it, filter has been cleaned about a month ago,checked rubber boot and no visible cracks in it,it is a stock motor w/vance and hines longshots,been rejetted a month ago, yamaha dealer is unfortunately where I am headed if I cant get it figured out, I appreciate everyones help, keep it coming.

no diesel ??.lol

Did you get it fixed?  What was it?

no I still havent figured it out I bought a new rubber boot online and when it got to me it was the wrong one,the person who owned the bike before me didnt use the boot for a roadstar, so I am back to square one

do u have california emissions, or do you have the Air Injection still on the bike?

My '03 did the same thing. My problem was small pieces of clear plastic in my float bowl from the factory.

My '03 did the same thing. My problem was small pieces of clear plastic in my float bowl from the factory.

Exactly what was wrong with mine. Past a certain speed she'd just start balking and slow down to 30 wide open sometimes. Found out that the carbs weren't sealed right. Cleaning and tightening the bottom fuel pots and their gaskets fixed it right up. You might have a bit of a time finding new gaskets or seals, depending on what they look like, you might be able to make them cheaper than ordering them; they sell gasket material at parts stores, I would try that before spending money on a gasket that small.

i had a vstar 1100 that had an ignition coil crack open, mine were under the tank, i was running hard and hit a freak cold rain storm and the cold water sprayed up and hit the hot coil, and it cracked, any moisture, any at all would cause all kinds of hell. i found which one was bad by pulling the plugs and looking for the one that was fuel fouled, traced the plug wire up and removed the coil, i put it under a heatlamp for a few hours and checked to see where the moisture was coming out, then sealed it up with epoxy after it was dried out, mine was banging out at speed, acceleration was erratic, all kind of fun stuff on the highway. but, this sounds more like a fuel/vacumn issue, does yours have the siamesed kehin carbs? that sit in a "y" manifold that feeds the cylinders?

Come on man, just dying to know if you got this figured out. Lots of good suggestions here.

Long distance is tough and have not had hands on with hypercharger but from some of my readings It is vaccuum operated butterflys. they may be the point of problem if vaccuum hoses leak or diaphrams are old. springs?? If the butterflies open with throttle open but partially close during cruise speed would cause a fuel/air problem and low power.
Like I say just an educated guess from long distance. Had simular problem on Holley carb. vaccuum secondaries. At 75 plus would begin to surge like working gas pedal open to half and open etc---- I the pedd=al was lifted just a little bit to 70-72 would run steady..Good luck if not found. Sound like an under load is needed to find. Trial and error replace rebuild alot....

Sounds like you may be sucking air somewhere, try spraying some engine cleaner on the hoses and see if that makes a difference.

If you have one of those Halloween smoke machines, fill the intake with smoke and see where it comes out.

I have an 03 roadstar 1600 that is doing the exact same thing. Itll go through the gears just fine getting on the highway but when i try to maintain speed it sputters and runs like crap. Did you ever get yours fixed?

Everyone has the carb covered how about loose throttle cables...................or perhaps the little screw thing that ya tighten them too, I'm guessing this is rather new issure. I now with my old 77 I had all the weird issures but then again AMF's were alien bikes............have a great one! "T"

Sounds to me like it is starving for gas or has an air leak at the manifold. The reason it is only doing it when you are maintaining speed is you are actually compensating for it while getting up to speed. You probably don't realize it but you are most likely using more throttle than normal while coming up to speed... compensating for the low fuel to air mixture. When you back off to maintain speed is when you notice it.

With the bike in neutral, try holding it at around 2500 rmp and it will most likely spit and sputter.

I would first check for an air leak on the intake manifold (where the carb connects to the motor). If that's not it... time for a carb re-build.

IMHO I might add whenevr a "rejet" is done there is a big difference in the different jets manufacturers make,with my bike, people have had no luck using dynojet kits,.. the factory pro kits out perform them,this is given advice on a Honda board I belong to.Also like others have said check for leaks again,sometime those rubber boots can get tiny pinholes in them.
The air fuel mix screw only applies to idle & low throttle speeds,n I dont believe thats the problem.Are you using the choke a lot to start it up..on my bike its not good.Found it fouled the plugs n made it run poorly at speed.