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Honda gx160 rough running


resq12345's Avatar
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11-26-07, 04:22 PM   #1  
Honda gx160 rough running

Hello,

Have a Honda GX160 on a logsplitter which was leaking fuel from a (presumably) stuck needle valve. I found an inexpensive aftermarket carburetor and replaced it and the carb to engine gasket. Engine seemed to run fine, so I shut down and put away. Two weeks later, I started up and engine runs rough - engine runs hi / low at a fairly fast rate, almost like it is sucking in air - now for the weird part.

I removed the carburetor to see what was up. I noticed a small channel in the engine block behind the carb gasket that leads back out alongside the gasket (presumably to vent air in or out). When I reassembled the carb and put my finger over this hole, The engine ran beautiful.

It doesn't seem right to block this hole to solve the problem, as It appears to be there for a reason, but I'm wondering if the aftermarket carb is different, causing the hole to be too big?

Can anyone help?

 
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11-27-07, 12:02 AM   #2  
There should be no air vent or places where air can be drawn into the intake between the carb and the engine. If there is, then something is missing, broken, or wrong. Not sure which in your case.


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11-27-07, 08:37 AM   #3  
Posted By: cheese There should be no air vent or places where air can be drawn into the intake between the carb and the engine. If there is, then something is missing, broken, or wrong. Not sure which in your case.
I have attached a picture the show you what I mean





If you look at the picture, there is a channel that leads to the bottom of the carb. This channel leads to a hole in the carb, and there is a matching hole in the gasket.

 
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11-27-07, 10:54 AM   #4  
Ah, I was picturing a crack in the plastic manifold or mismatched parts. What you show is normal. That is a vent, as you suspected, but it doesn't lead to the intake. It is the bowl vent passage. If the engine doesn't run right without covering this, then there is a problem with the carb. Drop the bowl and look to see if there is water or trash in the bowl.


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11-27-07, 11:57 AM   #5  
Posted By: cheese Ah, I was picturing a crack in the plastic manifold or mismatched parts. What you show is normal. That is a vent, as you suspected, but it doesn't lead to the intake. It is the bowl vent passage. If the engine doesn't run right without covering this, then there is a problem with the carb. Drop the bowl and look to see if there is water or trash in the bowl.

Hello again.

First, let me say thanks for your effort in helping me - It is much obliged.

I removed the carb and dropped the bowl, and all seems to be fine. Now water, debris, or out-of-place looking stuff inside.

What's odd is that when I ran it for the first time, it ran fine for the 15 minutes or so that I ran it.

question - does this "bowl vent" vent in or out. By restricting it, am I causing a vacuum inside the carb and causing it to draw more fuel? If so, could there be another adjustment somewhere to compensate for this?, or am I restricting some outward flow of air?

any other ideas?

Thanks again for your help

 
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11-27-07, 11:38 PM   #6  
heh, don't thank me yet... I don't mind helping, but we'll see how much help I was once you get this thing running right.

When the carb is empty, and you put gas in it, the air in the bowl has to be able to escape, or the carb bowl will not fill. That is what the bowl vent is for, along with other things that can vary the air pressure in the bowl like temperature. I believe this vent is used on some of these carbs, and on others, the passage is blocked and it is vented through the bore of the carb if I remember right.

I think the problem you have is related to the gasket between the carb and manifold, creating a vacuum leak.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

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11-28-07, 07:10 AM   #7  
Posted By: cheese heh, don't thank me yet... I don't mind helping, but we'll see how much help I was once you get this thing running right.

When the carb is empty, and you put gas in it, the air in the bowl has to be able to escape, or the carb bowl will not fill. That is what the bowl vent is for, along with other things that can vary the air pressure in the bowl like temperature. I believe this vent is used on some of these carbs, and on others, the passage is blocked and it is vented through the bore of the carb if I remember right.

I think the problem you have is related to the gasket between the carb and manifold, creating a vacuum leak.


Well, that was my original thought, which is what let me to place my fingers in that area in the first place. The next thing I did was replace that gasket you metion with a new one, with no results.

I think my course of action at this point is to block this vent altogether and use the unit for a long while and see what happens. If something else goes wrong, I'm going to assume that I bought a bad aftermarket carburetor (cheaper not always better i guess) and replace it again.

The first carburetor was fine - the engine ran great, but if you didn't shut off the feul when you shut off the engine, two minutes later the carb would be dripping fuel

-presumably from that same vent we speak of


Hey, wait??????????

 
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11-28-07, 08:58 PM   #8  
The leaky carb probably just had a stuck needle and needed cleaning. Did you open it to see, or just replace it? I don't trust the cheap aftermarket chinese carbs anyway. What's strange is the fact that you said it ran fine to begin with, and now it is surging. Check the intake area well. It is a black composite that is hard and brittle. Sometimes it will crack if things don't geehaw when it's being put together. A crack in this will cause the surge/hunt you described. I had that same thing happen on a honda earlier this summer, with the same symptoms you described.

Did I just say "geehaw"!? Showing my southern heritage there I guess .


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

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