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Honda carbs


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#1 Fig OFFLINE  

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Posted October 24, 2016 - 05:58 PM

I have a Bunton walk behind mower that I bought new in 83 that has a Honda GV400, 11hp engine. Although the mower is in great condition, considering it's age, the carb started leaking fuel out the overflow tube. I managed to find gaskets, a float and float needle valve on line and I ordered the parts. In the meantime, I decided to dismantle and clean the carb. I was shocked to find the float valve did not appear to have a function in controlling fuel into the float bowl. Fuel enters freely thru an adjacent port. The float's function seems to be to seal the overflow port. The design has obviously been working but it doesn't make sense to me. Has anyone else noticed this? Thanks!

#2 boyscout862 ONLINE  

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Posted October 24, 2016 - 06:06 PM

Welcome to GTT. That is an interesting observation. I've never heard of that type setup before. Someone who knows more will be along to help. Download the engine manual from our Manuals Section. Good Luck, Rick



#3 Alc ONLINE  

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Posted October 25, 2016 - 05:32 AM

Welcome to GTTalk !  I've only worked on one Honda carb and if I remember there wasn't a way to adjust the float level . Maybe if you post your complete  engine model number and we could find and  post some diagrams of that carb for members to see . I did a search with just the GV400 but they had letters after it too so not sure if I was looking at the correct carb


Edited by Alc, October 25, 2016 - 05:34 AM.


#4 Fig OFFLINE  

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Posted October 25, 2016 - 07:30 PM

The engine is a vertical shaft, model GV400, Type ADAA serial number 2041828.

Alc, you are correct, the float is non adjustable. It has a plastic float with a fixed tab. The float needle has a rubber tip and I "hope" the needle valve seat is not damaged and will not leak fuel when I get the new needle installed. As I said before, I was astonished when i dismantled it and saw the float did not meter or control the incoming fuel. Frankly, I can't believe it doesn't leak and flood the engine even when the float needle works properly. Two things

are for sure, the engine was a true bulletproof work horse before the carb started leaking and I don't understand the finer points of carb design. If anyone can shed some light on this, I would really appreciate it. Thanks in advance!!


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#5 Alc ONLINE  

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Posted October 26, 2016 - 05:24 AM

Your carb seem similar to the one on my bil mower . It seems like the float pushes up on the needle valve and seat like any carb that I've taken apart only I have no idea on any float adjustments .  Here's a parts breakdown if anyone could have more knowledge  on these

carb.jpg


Edited by Alc, October 26, 2016 - 05:24 AM.


#6 Fig OFFLINE  

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Posted October 27, 2016 - 02:48 PM

Alc: yep that's the carb! The float "operates" just like any conventional float ; however, it does not appear to have a direct impact on regulating fuel coming into carb. The float needle seats into a passage that leads into the fuel overflow tube. I know this because if I use low pressure air at the overflow tube, it exits at the float needle valve port. Conversely if I use low pressure air at the Incoming fuel line fitting, it exits into the carb at a port adjacent to, but not metered by the float valve assy.
IMO, it appears the carb operates like this and proper operation is dependent upon two conditions: First the float bowl must have and maintain an airtight and leakproof seal between the bowl and carb via the o-ring seal/gasket. Second, the float needle valve assy must be able to seat properly to form an airtight and leakproof seal. Fuel coming into the carb will eventually cause the float valve to raise and the needle valve will seal against the seat of the overflow tube which creates a condition were the remaining airspace compresses until it equals the incoming fuel pressure from the tank and the fuel stops flowing. When the engine is running and drawing fuel from the bowl the float drops, air pressure drops and allows fuel to flow via gravity into the bowl and the cycle is repeated. The card failed when seal integrity failed at the overflow due to an aged rubber tip on needle valve. The loss of back pressure allowed fuel to keep running thru the carb and out the overflow tube. Anyway, that's what it looks like to me.
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#7 Alc ONLINE  

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Posted October 28, 2016 - 05:31 AM

I don't work on that many to know about the different types of float set-ups .   Sounds like it would work that way though , thanks for the explanation 



#8 Rustysteele OFFLINE  

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Posted November 05, 2016 - 06:11 AM

Are you sure you aren`t mixing up the overflow nipple with the inlet nipple? Honda engines are fairly common around here, and I`ve never seen a set up like you describe in my 30+ years of being a mechanic. You would have fuel pouring into the carb throat if the float didn`t control the fuel entering the bowl. It`ll be interesting to see what you discover on this!


Edited by Rustysteele, November 05, 2016 - 06:11 AM.

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