Carb problem?

I have been having this problem for awile now. Any time I hold 90+ mph on the highway after a bit the bike starts to cut power and even die sometimes. What happens is I bring it down to 70-75 for a bit and the power comes back. I can run 80-85 with no problems, but once I get to 90 it happens every time. Any ideas?

[rictus01]

Given no other information I'd say your setup is way out and it's running well lean at the top end (although it'd have to be way out), has the airfilter/carbs or exhaust been played with/ ever been on a dyno ?

But as you don't provide any information on modifications, or history of the problem, at best it's a guess.

try reading the This first.

Cheers Mark.

99 naked with K&N. Also has two bros slip on (that is how I bought the bike minus K&N)The problem happened with the stock filter as well. When I changed plugs they were a little moist so I would lean to the fact I am running a little rich. Could this be a carb sync issue as I haven't done that yet.

[rictus01]

rich running wouldn't cause that sort of power loss and would be visable as black smoke, you say it's was doing the same with the standard air filter as well? so does that mean it's always done it ( I take it you're not the first owner) ?

does it have standard jets fitted, needles been moved, choke slide(s) both free and not stuck ?

the otherside of that coin is an air leak and either the airbox/intake hose isn't on right, or a vacum hose is off.

whilst carb balancing will give a smoothness to the running, I've seen bikes with it way out and they don't show the signs you have mentioned.

Cheers Mark.

I am not the original owner, I have no idea what has been done to the carb inside. I would think a disconnected hose would cause issues through the hole power range, but I will look to see. I know it didn't happen when I first got the bike last spring, but I didn't do those speeds to often either. I have only noticed it since riding through the winter months in 20 or less degrees, although today was like 45 degrees when it happened. Some one told me it could be carb freezing. Does this sound like a possibility?

[Sid Squid]

All the above and also check for fuel starvation - kinked or partially blocked hoses for instance, fuel cap breather, pump operation. It might flow just enough fuel for a lesser speed, but 90 may need a dab more than restricted flow might allow for.
If yours is a model with evap control gear, any of the hoses or the canister could give the same problem, although as I'm aware that's only the Californian models, I'm not certain of what's fitted to bikes in your state.

Originally Posted by Sid Squid

All the above and also check for fuel starvation - kinked or partially blocked hoses (and/or filters) for instance, fuel cap breather, pump operation. It might flow just enough fuel for a lesser speed, but 90 may need a dab more than restricted flow might allow for.
If yours is a model with evap control gear, any of the hoses or the canister could give the same problem, although as I'm aware that's only the Californian models, I'm not certain of what's fitted to bikes in your state.

+1 Its fuel starvation, evidently it is only at the stage where it manifests with the fuel demands at 90+mph. If it was jetting it'd never do the 90mph

Its a blocked breather, or pipe/filter, possibly (perhaps quite likely) a small split in the vacuum pipe on the fuel tap.