1981 CB750 flooding on highway

[seth.mason]

I have a 1981 cb750c rebuilt the carbs two seasons ago. Never had any trouble with the bike until I get on the highway or going 55 plus mph. As soon as I get up to high speed for any length of time it starts to flood out (losing power, sounds like its not running on all cylinders). I changed the spark plugs, made sure they were gapped properly and then gave it another go. Ran fine for a while, even on the highway. Then after a full day of high riding it started sputtering on the way home, so I figured it was nothing went riding again and then it started flooding out sooner. As the summer has gone on it gets worse and worse. Then today I got up to 50 and it completely broke down. The bike only has four gears however, I don't think that has anything to do with it. I've never vacuum synced the carbs, in my opinion I believe the cylinders are flooding because some are getting too much fuel (duh). I have the carbs bench synced, which could mean some of the cylinders are getting too much fuel. I changed the coils the same time I rebuilt the carbs so I believe I'm getting enough spark. But, other than that I'm sure what it could be. Help me out fellas!

[motogrady]

u sure its floodin?

had the same symptoms, but it was the old fuel lines getting hot
from the air comimg off the hot motor at cruising speed,
line would suck into itself, collapse, pinch off fuel supply
when it got real rubbery, shut down line would cool,
fill with cold petrol, expand and you'd never know it the next day
in the garage.  I thought it was electrical, coil breking down when it got hot,
couldn't see the forest for the trees................good luck guy

[TOOLS1]

I doubt it is flooding. It sounds like it is just the opposite. You could have dirt in the fuel system, or the tank vent is plugged. Another thing that is common on the DOHC bikes is the charging system is not keeping the battery charged, and it is loosing spark.
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