Float Height - What does it affect?

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Sep 6, 2006
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#1
I pulled my carb apart tonight to clean it and found that the float was way out of spec. The manual calls for it to be between 5.5 and 7.5 mm above the mating surface, while it was about 2 mm. The needle and seat look to be in good shape so all I did was bend it back within specs.

My question is what will this do to the performance of the engine? The last time out it was fouling plugs. I was thinking it was the jetting but now am not so sure. What do you think???
 
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#3
Yes, the float height slightly affect the air-fuel mix, so if you have an high float heigh you will run slightly leaner than stock and vice-versa.
The float height affect all the throttle valve positions (from 1/8 to full open).
 
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#4
Float hight effects the mainjet probably the most since you might be getting to much or too little fuel filling the bowl when the main jet is trying to work. But it does effect throughout the entire throttle range.
 
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#5
Thanks for the information. I was having the most problems with throttle response in the lower gears, which seemed to clean out in 3rd and higher. Both times it fouled plugs on the last ride was after I had been sitting with the engine off for a short while. When I started it up and took off, it was fine for about 20 yards and then acted as though it had run out of gas. The plug was wet and black in both cases. Here's hoping that the float was at least part of the problem! :cool:
 
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#6
Charlie Mix said:
Yes.... so if you have an high float heigh you will run slightly leaner than stock and vice-versa....
I thought it was the other way around. But that may be semantics as I consider a "high" float height meaning when the carburetor is turned back right side up. So, in my thinking, the further from the deck it measures, the "lower" the float would be. You may be meaning "high", as measured from the deck.
 
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#7
2strokerfun said:
I thought it was the other way around. But that may be semantics as I consider a "high" float height meaning when the carburetor is turned back right side up. So, in my thinking, the further from the deck it measures, the "lower" the float would be. You may be meaning "high", as measured from the deck.
The float height is measured in mm. from the mating surface to the highest point of the float.
"High" means an higher number compared to the stock value so the jetting shall be leaner than stock because in this way the fuel level in the bowl shall be lower than stock.
 
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#9
Most plugs foul because the lower end is to rich meaning from 0 throttle to 1/4 throttle. The slow jet controls this range up to a half throttle as well as the needle jet. Leaning the slow jet will make the engine run leaner at idle and up to a half throttle. You can also lower the needle jet to lean the bottom out a little.