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Float bowl puzzlement

  • Thread starter Thread starter suzukizone
  • Start date Start date
S

suzukizone

Guest
Discussing various carb issues at work, a question arose.

If a float level is set to as have too high a level of fuel in bowl, exactly how does this translate into too rich a mixture?

If the only route from the bowl into the carb throat is via the pilot jet and then main jet through the needle jet, how does that small amount of fuel alter the mixture if the jet sizes control the maximum amount of gas allowed to flow.

Not disputing this, I know it does but couldn't propose the actual reason. Wouldn't the extra gas be ejected through the overflow vent(if it rose that high anyway).

Well just a puzzlement in trying to explain the reality of the effect.

DH
 
First of all, your '81 does not have any overflow provisions. By the time the fuel level gets that high, it simply flows through the throat, into the cylinder or out through the filter.

Now, to answer your question:
A high float level richens the mixture simply because it does not have to be lifted as high to get into the airstream. Carbs work due to pressure differences. Air flowing through the venturis drops a bit of pressure as it speeds up. That lower pressure is meant to bring a certain amount of fuel that is "x" amount below the carb throat. If the level is closer to the carb throat, it will be lifted into the airstream with less of a pressure differential (sooner than intended) or, given the amount of the differential, will bring more gas up.

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Float bowl puzzlement

Thank you Steve for the enlightenment. All head scratching ceased,....for the moment.

As for the overflow on my carbs, I thought those were the 2 black hoses that come out of the junction lines connecting the pairs or carbs. Maybe they are just some sort of vent?

Thanks again!

DH
 
Yes, those are just vents. The float bowls need to be referenced to atmospheric pressure.

Steve explained the fuel level very well. The difference in even a tiny change in fuel level is quite dramatic, a small change makes a large difference.
 
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