Runs like crap after a few minutes at high speed

[MaParkerColo]

So I normally am not too squidly, but last week I was coming home from work on the tollroad and found myself working my way to the front of the pack. Ended up running right around 100mph for a few minutes coming up a hill. After a couple of minutes it started losing power like I was running out of gas. I managed to run the speed limit by keeping the throttle wide open in 5th and took the next exit. I pulled into a gas station to fill the tank thinking that I had run out of fuel. It was low, but certainly not empty, but I topped it off anyway. Seemed to run OK on the way home.

My thought is that at that speed I either out stripped the fuel pump, or more likely had a problem in the float bowels. I have not adjusted the float levels since I rebuilt the carbs several years ago, but have not reason to think they are off all of a sudden. I also have had the vent tubes cause problems on some bikes and usually remove the tubes so that there is less resistance and it is easier for the pressure to equalize. This is a fairly common occurrence on older UJM's with vacuum actuated petcocks resulting in fuel starvation

Anyone have any FZR specific experiences like this that wants to offer other suggestions before I decide to dig into the carbs?

Thanks,
Mark

[reelrazor]

Check the fuel tank vent. It's in the fuel filler cap.

Start throwing real demand (uphill-heavy throttle for a decent amount of time)at the tank, and pulling a vacuum at the tank can be a real issue. Your experience with juat keeping it going after it occurred is making me think this could be your issue.

Make it do it again, and hurry up and pull the fuel cap..you hear a sucking sound when it comes off?

Vent is in the cap alongside the lock cylinder.

[GreyImport]

I presume the 600s have a fuel filter?

Going uphill at speed might cause any grunge in the filter to move and restrict the flow......this is how one of my cars tells me the filter needs replacing.

[HybridSport600]

Low float bowl fuel level (pump spitting fuel into bowl, instead of pouring) along with some worn out emulsion tubes will cause this exact problem, the tubes are allowing more air into the bowls and will pull more fuel at mid to high rpm range. and with low fuel level in the bowl and it cannot meter the fuel to air ratio correctly. and going up hill will make this problem worse. and will also be a common problem avery time the tank gets to the reserve level. I have tackled this problem before in my shop, and almost everytime it is the tubes . take the tubes out and look for oval shaped openings where the needle enters at the top. let me know!