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Discussion Starter · #1 ·
Anybody DIY one of these?


s-l1600.jpg

I hollowed out an old drain screw, but couldn't figure a way to attach the fuel line reliably. Seems like it would be a great tool to have to confirm/rule out float probs.
 

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I've made a couple different ones for various carbs. Most drain screws are brass and a short piece of small copper tubing can be easily soldered into a hole drilled through it.

.........Paul
 

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I used a conical shaped rubber piece from a vacuum tester.

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Yes, turn off the gas, pull the bowl drain screw out, hold the rubber piece in the hole and the clear tube up, turn on the gas and see where the level settles.
 

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Ok... I totally understand that.. my question is WHERE should the fuel level be? , according to your carbs??? Float levels are still on my "to learn list", along with "dwell and timing".... I have read a "ka-f**k-ton" of threads about setting the proper "float bowl level" with the carb being upside down... and a measurement taken (please correct me if I'm wrong) from the flange (where the float bowl seats to the carb body) and the "bottom" of the float bowls as the needle properly seats... this is done "dry" and it is kind of a guess as to the "actual" fuel level inside the bowl... With using this tube.. you can have an actual "fuel level"... but where should this level be in accordance to the "dry" measurements? The same???
 

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Discussion Starter · #11 · (Edited)
I suppose you could come up with an approx measurement based on the middle of the float and the sealing surface (when the float is at the cutoff point). I've not seen any fuel level measurements listed for vintage Honda stuff. I'm more interested in seeing if the levels are the same side to side, rather than a particular measurement.
 

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That makes more sense.. gotta get the levels correct on my 73 450, cleaned carbs REAL good. Starts and idles beautiful (after the left carb "kicks in")but has no "top end speed.. basically the same thing my S-90 did till I got it sorted ...
Gonna try "choking" the carbs when it "bogs down", richening the mixture.... see if I'm on the correct path..
 

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I've used the clear tube method on Kawasaki Concours carbs after doing some jetting mods. I had a bench setup to mimic the angle the carbs are at while on the bike. Works very well even after being very careful setting the float height by measurement.

I haven't done this on CB carbs but given the information on other carbs it would seem that a fuel level 3 + or - 1/2 mm below the edge of the float bowl would be a good place to start. The overflow tube has it's hole drilled so it is level with the edge of the float bowl so it has to be lower than that.

I would hold the tube directly inline with the overflow tube, so right above the drain screw location. You can make marks on the tubing once you figure out your setup.

Since I have 8 carbs to set up in the near future I'll take the time to make a bench set up so will post some pictures. BTW if you are doing it on a bench you can use low odor solvents rather than gasoline.
 

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Rob, just make a gauge from stainless or thick plastic (that doesn't react to fuel), per the guidance in the Honda Service manual. Then, you can hold the float up with it and open the petcock. If you get more than a very slow drip, the float is too low; if you have to lower it more than a hair to get some flow, it is too high. Snap the bowl back on, and done.
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That 20.0 is the measurement to the step part of the slot. Just cut the rest to span the bowl seat, and the deeper step to clear the jets. See P. 53 of the service manual, paragraph 3.6.B.5
 

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Thanks.. one thing to concider if u have brass floats (other than getting pinholes) is that they "bend"..,I kept setting the bowl level correctly and the motor was still starving for fuel... (the S-90)
Long story short, when I origionally tore into the carb(it sat for over 10 years).. I noticed the floats "bent" weird... wasn't sure how this occured.. so I bent them to (what I thought) was the correct "shape"...
After taking that carb on and off multiple times.. I tried the "bowl removed, level set, petcock opened"... and the level was correct....
HOWEVER.. as I reinstalled the bowl, I felt a little "drag" or contact... the float was contacting the bowl on the side..
The bent floats, apparently was done by the PO.. I wonder if it was due to floats making contact...
I am discovering not only with my Honda, but my Triumph... YES, the factory Manuel is a must...but NOTHING is cut and dry with 40plus years of a motorcycle passing through God knows how many hands.. and not all were certified master mechanics!!!
 

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Using the tube I see that the fuel level is even with the flange the bowl sets in. I don't remember where I found this information years ago but has worked for me.
 

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When I set my floats with the gauge, I will make one of these, see if they match each other and see where the fuel level is in relation to the carb body..
 

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Discussion Starter · #18 ·
Rob, just make a gauge from stainless or thick plastic (that doesn't react to fuel), per the guidance in the Honda Service manual. Then, you can hold the float up with it and open the petcock. If you get more than a very slow drip, the float is too low; if you have to lower it more than a hair to get some flow, it is too high. Snap the bowl back on, and done.
View attachment 268280

That 20.0 is the measurement to the step part of the slot. Just cut the rest to span the bowl seat, and the deeper step to clear the jets. See P. 53 of the service manual, paragraph 3.6.B.5
Its more about seeing the actual level of GAS in the float bowl while running, since that affects the lean/rich fuel mixture. Measuring the float height upside down is a good starting point, but with bent, non stock floats etc, I want to know whats REALLY going on.
 

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Upside-down readings can be incorrect, as the weight of the float can depress the spring in the needle a bit. When I do the check with the carb in my hands, I first turn it upside-down to seat the needle, then turn the carb to vertical, with the float hanging down touching the needle. This is the position Honda says it should be done, BTW; see figure 3.132 and paragraph 3.6.B.5 in the service manual.
 

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Discussion Starter · #20 · (Edited)
Yes, i'm familiar with the classic float setting procedure from the manual. The float bowl sight gadget is to use in addition to setting floats via the FSM.
 
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