Author Topic: 350F Float Height External Check - What's Correct?  (Read 1190 times)

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Offline OakBehringer

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350F Float Height External Check - What's Correct?
« on: July 24, 2009, 02:44:59 PM »
In an effort to figure out why my bike is running lean I may be pulling the carbs today. When doing an external check w/tube, how high should the gas be in the bowls?

Thanks,
Adam
1974 350 Four - SOLD
1966 CL160
1981 XS650
1972 CT70

Finished CB350F

HELLS BANANAS

Offline fmctm1sw

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Re: 350F Float Height External Check - What's Correct?
« Reply #1 on: July 24, 2009, 03:55:01 PM »
I'm interested to see what kind of answers you get.  I've been skeptical of my "set it and forget it" 21mm float height.  I wonder if you could theorize that you want it above the lowest point of the idle jet but not so high that it's covering the holes in the idle jet?  I wonder what point that equates to on the outside of the carb?  There can't be a lot of distance from the bottom of the idle jet to those holes I wouldn't think...
Quote from: 754
Dude is that a tire ? or an O-ring..??

Quote from: inkscars
This is not a pod thread
This is not a #$%* on my vacuum gauges thread
This is a help or GTFO thread.

1973 CB350F
1973 CB350G
1975 CB550K
1983 GL650I
1973 CB750K3 (http://forums.sohc4.net/index.php?topic=92888.0)
1984 Kawasaki KLT-250 (AKA 3 wheeler of death)
1994 Honda TRX300
1999 Honda TRX250

Offline OakBehringer

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Re: 350F Float Height External Check - What's Correct?
« Reply #2 on: July 24, 2009, 04:04:37 PM »
Yea, I'm almost sure that my new needle valves are set spot on, as I did them a few weeks ago, which is why I want to do this.

The volume of gas in the bowl determines how much suction is required to get gas through the jets and into the cylinders, which is what leans out or enriches your mixture.
1974 350 Four - SOLD
1966 CL160
1981 XS650
1972 CT70

Finished CB350F

HELLS BANANAS

Offline fmctm1sw

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Re: 350F Float Height External Check - What's Correct?
« Reply #3 on: July 24, 2009, 04:08:40 PM »
Yea, I'm almost sure that my new needle valves are set spot on, as I did them a few weeks ago, which is why I want to do this.

The volume of gas in the bowl determines how much suction is required to get gas through the jets and into the cylinders, which is what leans out or enriches your mixture.

Yes, but I was thinking that that the level has to be at least as high as the lowest lowest passage on the idle jet?  Other wise it would pull air.  Guess not though since you could compensate with the air screw...
Quote from: 754
Dude is that a tire ? or an O-ring..??

Quote from: inkscars
This is not a pod thread
This is not a #$%* on my vacuum gauges thread
This is a help or GTFO thread.

1973 CB350F
1973 CB350G
1975 CB550K
1983 GL650I
1973 CB750K3 (http://forums.sohc4.net/index.php?topic=92888.0)
1984 Kawasaki KLT-250 (AKA 3 wheeler of death)
1994 Honda TRX300
1999 Honda TRX250

Offline OakBehringer

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Re: 350F Float Height External Check - What's Correct?
« Reply #4 on: July 24, 2009, 04:24:53 PM »
Well, yea, of course it would have to be at least that high :)
1974 350 Four - SOLD
1966 CL160
1981 XS650
1972 CT70

Finished CB350F

HELLS BANANAS

Offline fmctm1sw

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Re: 350F Float Height External Check - What's Correct?
« Reply #5 on: July 24, 2009, 04:29:54 PM »
Well, yea, of course it would have to be at least that high :)

But then not so high as to cover those timy emulsion holes in the jet since they are designed to pass air right?  The distance between those two points is relatively small if I remember from cleaning them.  Four words:  See-through float bowls! 
Quote from: 754
Dude is that a tire ? or an O-ring..??

Quote from: inkscars
This is not a pod thread
This is not a #$%* on my vacuum gauges thread
This is a help or GTFO thread.

1973 CB350F
1973 CB350G
1975 CB550K
1983 GL650I
1973 CB750K3 (http://forums.sohc4.net/index.php?topic=92888.0)
1984 Kawasaki KLT-250 (AKA 3 wheeler of death)
1994 Honda TRX300
1999 Honda TRX250

Offline fmctm1sw

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Re: 350F Float Height External Check - What's Correct?
« Reply #6 on: July 24, 2009, 06:12:21 PM »
As pointless as this may have been, I tried to theorize where the fuel should be as it relates to the jets and also where the level would be on the bowl if you could look through it. 

I started with the slow jet.  The highest point I imagine you would want fuel to be on the idle jet is just below the tiny passages near the top that also air to pass through to create a froth effect for the fuel.  That point is noted in the first picture as the mark above the idle jet.  At the lowest, you would need it to be at least covering the slotted screwdriver area at the bottom of the jet.  That's a pretty wide range. 

I applied the same logic to the main emulsion tube.  Given the length of the tube and the amount of holes in it, I began to wonder if the fuel level is supposed to cover some of those passages.  Assuming it ISN'T though, the pen mark near the lower end of the main jet passage denotes the point where the holes in the emulsion tubes start.  I wouldn't imagine you'd want it much lower than that. 

Looking closer at the emulsion tube, there are 5 vertical holes with another set of 2 near the middle.  Just as I thought that you may want some of the covered with fuel, you probably don't want all or most of them covered either.  The next pen mark up on the main jet passage denotes where the set of 2 holes starts (where they would just remain uncovered). 

The last picture illustrates the minimum I level I determined form the main jet passge and the highest I think the idle jet could take as it relates to the float bowl.  The upper mark is hard to see in one of the photos but it's right at the edge of the shadow.
Quote from: 754
Dude is that a tire ? or an O-ring..??

Quote from: inkscars
This is not a pod thread
This is not a #$%* on my vacuum gauges thread
This is a help or GTFO thread.

1973 CB350F
1973 CB350G
1975 CB550K
1983 GL650I
1973 CB750K3 (http://forums.sohc4.net/index.php?topic=92888.0)
1984 Kawasaki KLT-250 (AKA 3 wheeler of death)
1994 Honda TRX300
1999 Honda TRX250