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I have a Honda Gx 120 that runs a pressure pump on a spray rig designed to spray Tree Orchards. The problem I am having is that the engine and pump are very close to the ground as the spray rig travels across the field and it is very dusty. After just a few passes through the field, I need to stop and blow out the air cleaner.
I thought one solution to my problem would be to diy myself a type of "snorkel" system to get the air filter up and out of the dusty area.
I took off the air filter and clamped a rigid hose to the collar where the air filter fits in. I extended the hose about 3 feet up and hooked it to the top of the spray rig. I then attached another air filter at the end of the hose. Now the engine runs rough. At full throttle and with the choke open it surges very badly. I can smooth out the surge by either slowing the engine down or closeing the choke about half way.
I can only assume that by extending the filter upwards, I have changed the vacuum or airflow into the carburetor. Is there any way to make an adjustment for this? Is it bad to run the engine at half choke for extended amounts of time?
Thank you for your help

Did you put a K&N style filter on and did you attach the hose well enough to not put pressure on the carb to create an air leak?

Not a k&N Filter. I put this filter on the other end of the hose that I attached to the carb.
https://www.greenpartstore.com/thum...er-element-aw26796-medium.jpg&maxx=300&maxy=0

I have the hose at the carb pretty well clamped down so I do not think there is an Air leak. Are you saying that too much airflow can cause this problem? I was assuming I was creating a restriction.

If you have to use the choke then you are running in a too lean fuel to air condition. The choke cuts off some air and richens the mixture. As long as you are not running overly lean, running with the choke partly closed should not hurt the engine. Too rich might cause some carbon buildup or some gas getting into the crankcase and contaminating the oil.

DBICK said:

Not a k&N Filter. I put this filter on the other end of the hose that I attached to the carb.
https://www.greenpartstore.com/thum...er-element-aw26796-medium.jpg&maxx=300&maxy=0

I have the hose at the carb pretty well clamped down so I do not think there is an Air leak. Are you saying that too much airflow can cause this problem? I was assuming I was creating a restriction.

Click to expand...

I was thinking the weight of the snorkel might be pushing the carb down and causing an air leak at the gasket not the snorkel having a leak. Yes I was thinking you are getting too much air.

Try shortening the snorkle to just enough to connect the air filter. Like 1 or 2 inches and see how it runs.

Thanks for the replies.
I went back out today to take some pictures. I thought it would be easier for everyone to see what I am trying to do. Here is a link to the imgur album:
https://imgur.com/a/BP7a3G5

The engine runs smoothly without the air filter installed. As soon as I place the hose over the collar, the engine either dies or starts running very rough. Even without the air filter at the top, just the length of the hose seems to make it run rough. I tried it with a shorter piece of hose, maybe 1 foot long and I had the same results. The only way I can get it to run a little bit smoother is to close the choke a bit.

If there is no way to adjust the carburetor for this, what else might I try? Is there a different filter/housing that would work in these dusty conditions? Until we get some rain here in California, the field is just so very dusty.

Thanks again for your help

I see problems.

That is a lot of weight pushing down on the carb. I think it might have an air leak behind the gasket. Try holding up all the weight of that hose while it's running and see if it smooths out without the choke partly closed.

DBICK said:

I have a Honda Gx 120 that runs a pressure pump on a spray rig designed to spray Tree Orchards. The problem I am having is that the engine and pump are very close to the ground as the spray rig travels across the field and it is very dusty. After just a few passes through the field, I need to stop and blow out the air cleaner.
I thought one solution to my problem would be to diy myself a type of "snorkel" system to get the air filter up and out of the dusty area.
I took off the air filter and clamped a rigid hose to the collar where the air filter fits in. I extended the hose about 3 feet up and hooked it to the top of the spray rig. I then attached another air filter at the end of the hose. Now the engine runs rough. At full throttle and with the choke open it surges very badly. I can smooth out the surge by either slowing the engine down or closeing the choke about half way.
I can only assume that by extending the filter upwards, I have changed the vacuum or airflow into the carburetor. Is there any way to make an adjustment for this? Is it bad to run the engine at half choke for extended amounts of time?
Thank you for your help

Click to expand...

How did you decide that after a few passes through the field, the air cleaner was so dirty it needed attention? The only accurate way to determine when an air filter element needs to be cleaned or replaced is with a restriction gauge.

The air filter element should be close to the engine, not at the opposite end of the long intake tube. This may be hard to do on an engine that wasn't designed for a commercial-grade air filter system.

I decided it was time to clean the air filter when I looked back and the engine had died. I checked everything out and the only problem was the element was packed with powder. After I cleaned it/replaced the element it ran fine for another few passes then it was clogged again.

I also noticed that where I clamped the hose it was a bit pinched. I loosened that and straightened out the hose. I do not feel that there is any weight pushing down on the carburetor since the entire apparatus is clamped to that riser on the spray rig.

So it looks as if I am barking up the wrong tree here and what I wanted to accomplish isn't possible. Anyone have any other ideas I can try except praying for rain to knock down the dust?

DBICK said:

I decided it was time to clean the air filter when I looked back and the engine had died. I checked everything out and the only problem was the element was packed with powder. After I cleaned it/replaced the element it ran fine for another few passes then it was clogged again.

I also noticed that where I clamped the hose it was a bit pinched. I loosened that and straightened out the hose. I do not feel that there is any weight pushing down on the carburetor since the entire apparatus is clamped to that riser on the spray rig.

So it looks as if I am barking up the wrong tree here and what I wanted to accomplish isn't possible. Anyone have any other ideas I can try except praying for rain to knock down the dust?

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Well if you are sure of no air leaks or unmetered air coming from after the carb you could try a high altitude jet in your carb.... They are cheap enough and you got more money on your new setup than a new jet....... Sea level air pressure is 14.7 PSI... Higher altitudes are going to be less air pressure.... You have created, with your snorkel setup a lower air pressure situation.... That is why you can find a sweet spot with the choke partially closed......

Just a thought Mon Ami ~!~!

Let us know Mon Ami ~!~!

Scratch the last post I did.... I'll get back later...

I agree with Blaze maybe you getting unmetered air from where the carb connects to the engine.... while it's running spray some WD-40 behind the carb on the gaskets and see what happens.... If it levels out then that is your issue......

I still have one more post after you answer this one ~!~!

If you are not getting the extra air from behind the carb then I do have a solution for you .....

Waiting on your response ~!~!

Anybody remember the old Hillborn fuel injection systems for racing engines? They had varying length velocity stacks to use, which affected engine performance. I'm thinking that snorkel is acting much the same way.

http://hilborninjection.com/wp-content/uploads/2015/11/260F8B_EL-600x600.jpg

I was thinking the same thing.

Thanks again for all the replies. I will try there WD-40 trick and report back next week.

DBICK said:

Thanks again for all the replies. I will try there WD-40 trick and report back next week.

Click to expand...

Yes let me know something.... But I will tell you now.......... IF you don't have unmetered / unwanted air coming in after the carb then get you some thumb / micro drill bits, a whole set of them........ Then find the one that fits into the jet opening....

Go up 1 size, or 2 sizes larger than the original factory opening..... Don't worry 1 size up is only a small fraction just enough to take some brass off... We do that all the time when carbs get varnished and gummed real bad...... You are making the jet hole a teeny tiny bigger to allow for more fuel flow to get in there with the air mix......

Blaze and C Purvis will agree with me on this ....... BTW Blaze are your sides still splitting LMAO ???????

Plus Tard Mon Ami .....

Boudreaux In Eunice La. said:

Yes let me know something.... But I will tell you now.......... IF you don't have unmetered / unwanted air coming in after the carb then get you some thumb / micro drill bits, a whole set of them........ Then find the one that fits into the jet opening....

Go up 1 size, or 2 sizes larger than the original factory opening..... Don't worry 1 size up is only a small fraction just enough to take some brass off... We do that all the time when carbs get varnished and gummed real bad...... You are making the jet hole a teeny tiny bigger to allow for more fuel flow to get in there with the air mix......

Blaze and C Purvis will agree with me on this ....... BTW Blaze are your sides still splitting LMAO ???????

Plus Tard Mon Ami .....

Click to expand...

I agree.
Yes, my sides still hurt especially when I think of the little present waiting for someone.

Thank you guys. Sorry for the late reply. Holidays and all that.

I tried the wd40 trick and the engine did not run better. We actually got some rain here in CA so the field will not be so dusty for a few months. I probably will just hook things back up as normal and try this snorkel setup next summer. Thanks for the tip on enlarging the jet. I appreciate all the help.

Thanks for the reply............ Yes do the jet trick in your spare time to see if it works..... Which it will and you are saving time like that when you need the snorkel.....

Don't be a stranger Mon Ami ~!~!

cpurvis said:

How did you decide that after a few passes through the field, the air cleaner was so dirty it needed attention? The only accurate way to determine when an air filter element needs to be cleaned or replaced is with a restriction gauge.

The air filter element should be close to the engine, not at the opposite end of the long intake tube. This may be hard to do on an engine that wasn't designed for a commercial-grade air filter system.

Click to expand...

Down here all of the push mowers used to be fitted with snorkels and that includes the GXV 120 Hondas.
Now Briggs have taken over Victa most have reverted to the shite system you have been lumbered with where the air filters need to be replaced every 4th mow.


Honda marketed a snorkel for the 120, 140 & 160.
All used the same air filter and Honda recommended fitting a smaller jet although I have never done that because they seem to run fine with std jetting.
On the commercial mowers, Victa used a larger diameter tube


So you might need to use a larger diameter tube.
Note the larger tube used the same filter.

If you are needing to run with the engine choked that would imply that the engine is getting too much air.
have you checked for a partially blocked jet or emulsion tube ?