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This engine is driving me mad.It starts fine,but will not rev up When I open the throttle the revs rise and then the engine just starts to misfire.I have cleaned and rebuilt the carb many times all to no avail
Any ideas??

Phil

This cleaning guide for GX series carbs from Honda should help you.

http://honda-engines-eu.com/en/images/59138.pdf

You can also look under "Service" and then "Service Videos". They have a short video of how to clean one of them too.

Honda Engines Europe EEC

bwdbrn1 said:

This cleaning guide for GX series carbs from Honda should help you.

http://honda-engines-eu.com/en/images/59138.pdf

You can also look under "Service" and then "Service Videos". They have a short video of how to clean one of them too.

Honda Engines Europe EEC

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Thanks for that I'll try again! only harder

Let us know how it goes for you. I've cleaned them before I knew about how to remove the pilot jet, and wondered why they didn't run better too.

:smile: When you take the main jet out, becareful and not lose the E-tube, as they fall out quite easy.

Buckshot 1 said:

:smile: When you take the main jet out, becareful and not lose the E-tube, as they fall out quite easy.

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Definitely not the carb:thumbdown:

philrose said:

Definitely not the carb:thumbdown:

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:smile:I do not understand your post.

Buckshot 1 said:

:smile:I do not understand your post.

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Just saying cleaned the carb AGAIN as per video.Result no change!:frown:

Have you replaced all of the gaskets associated with the carb? Using the old ones isn't a good idea as there may be tears you don't necessarily notice, and they do tend to "seat" when used, and if not lined up just right when you re-install them, they may cause air leaks that will give you problems.

What does it do when you try to hold the governor arm still while it's running? Is that fine little spring on the governor arm, sometimes called an anti-surge spring O.K. Maybe the governor needs to be adjusted.

How about the valves? Has the clearance been checked?

bwdbrn1 said:

Have you replaced all of the gaskets associated with the carb? Using the old ones isn't a good idea as there may be tears you don't necessarily notice, and they do tend to "seat" when used, and if not lined up just right when you re-install them, they may cause air leaks that will give you problems.

What does it do when you try to hold the governor arm still while it's running? Is that fine little spring on the governor arm, sometimes called an anti-surge spring O.K. Maybe the governor needs to be adjusted.

How about the valves? Has the clearance been checked?

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New gaskets fitted,governor set and fine spring ok.
Perhaps I should check the valve clearances !

You've got to be getting close to getting this mystery solved!

Intake 0.15 + or - 0.02 mm

Exhaust 0.20 + or - 0.02 mm

Even after re-cleaning the carb several times, have you checked the FLOW of gas with the carb bowl off and using your finger to raise and lower the float? I've seen other engines start fine because gas will come down through the fuel system and fill up the float bowl very slowly. Then when you start it it has just enough gas to throttle up, but then burns it all and starts sputtering and coughing and stumbling as yours is. Sounds like a "Fuel Starvation" problem to me. Check for good fuel flow from the tank, filter, lines, and where it goes into the carburetor. Maybe a tiny piece of foreign matter is causing the lack of fuel flow? Perhaps some varnish over the fuel inlet filter screen in the carburetor? Hope this helps. Dave

DaveTN said:

Even after re-cleaning the carb several times, have you checked the FLOW of gas with the carb bowl off and using your finger to raise and lower the float? I've seen other engines start fine because gas will come down through the fuel system and fill up the float bowl very slowly. Then when you start it it has just enough gas to throttle up, but then burns it all and starts sputtering and coughing and stumbling as yours is. Sounds like a "Fuel Starvation" problem to me. Check for good fuel flow from the tank, filter, lines, and where it goes into the carburetor. Maybe a tiny piece of foreign matter is causing the lack of fuel flow? Perhaps some varnish over the fuel inlet filter screen in the carburetor? Hope this helps. Dave

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Hi Dave
Thanks for that suggestion,never considered the fuel flow.I will try that today.Just to clarify the valve clearance settings,is it 0.006 inch I/L and 0.008 inch O/L ?
Phil

philrose said:

Hi Dave
Thanks for that suggestion,never considered the fuel flow.I will try that today.Just to clarify the valve clearance settings,is it 0.006 inch I/L and 0.008 inch O/L ?
Phil

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Intake is 0.006 (+ or - 0.001 inches)
Exhaust is 0.008 (+ or - 0.001 inches)

Checking the fuel flow is a good idea too. Hadn't thought if it either. Take a look to see if there's something inside the fuel tank blocking the filter inside it.

bwdbrn1 said:

Intake is 0.006 (+ or - 0.001 inches)
Exhaust is 0.008 (+ or - 0.001 inches)

Checking the fuel flow is a good idea too. Hadn't thought if it either. Take a look to see if there's something inside the fuel tank blocking the filter inside it.

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Thought I'd post these specs for Honda Engines.

Honda Small Engine Intake & Exhaust Valve Clearances

Model Series

Intake Valve Clearance

Exhaust Valve Clearance



GX640

0.10-0.14mm ( 0.004-0.006in )

0.18-0.22mm ( 0.007-0.009in )



GX100

0.15 +/- 0.04mm

0.20 +/- 0.04mm



GX120

0.15 +/- 0.02mm ( 0.006 +/- 0.001in )

0.20 +/- 0.02mm ( 0.008 +/- 0.001in )



GX160

0.15 +/- 0.02mm ( 0.006 +/- 0.001in )

0.20 +/- 0.02 mm ( 0.008 +/- 0.001 in )



GX670

0.15 +/- 0.02mm ( 0.006 +/- 0.001in )

0.20 +/- 0.02mm ( 0.008 +/- 0.001in )



GXV120

0.15 +/- 0.02mm ( 0.006 +/- 0.001in )

0.20 +/- 0.02mm ( 0.008 +/- 0.001in )



GXV140

0.13 - 0.17

0.18-0.22



GXV160

0.15 +/- 0.02mm ( 0.006 +/- 0.001in )

0.20 +/- 0.02mm ( 0.008 +/- 0.001in )



GXV270

0.15 +/- 0.02mm ( 0.006 +/- 0.001in )

0.20 +/- 0.02mm ( 0.008 +/- 0.001in


GX360

0.12 +/- 0.02mm ( 0.005 +/- 0.001in )

0.20 +/- 0.02mm ( 0.0078 +/- 0.0008in )

:smile: Do you have the E-Tube under the main jet?

Buckshot 1 said:

:smile: Do you have the E-Tube under the main jet?

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Don't know.What does it look like?

He's talking about the emulsion tube. It's that part they poked out after taking the main jet out that has a bunch of holes along the sides.

The part they poked out in the video about cleaning the carb, that is.

bwdbrn1 said:

The part they poked out in the video about cleaning the carb, that is.

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Yes it's got the emulsion tube,I don't think the carb would work without it.And I have cleaned out all the holes.

philrose said:

Yes it's got the emulsion tube,I don't think the carb would work without it.And I have cleaned out all the holes.

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That tube helps break the gas down into smaller drops, mixed with air to create a combustible mixture. An engine can't run on liquid gasoline, has to be fine mist, then with engine heat ~~~ vapors~~~.

DaveTN said:

That tube helps break the gas down into smaller drops, mixed with air to create a combustible mixture. An engine can't run on liquid gasoline, has to be fine mist, then with engine heat ~~~ vapors~~~.

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I know what an emulsion tube is and for, just never heard it referred to as an E tube.

Phil

philrose said:

I know what an emulsion tube is and for, just never heard it referred to as an E tube.

Phil

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:smile: Common term used for us that use the GX for racing. Engine will run with a carb not having an E-tube, will start and idle with choke on but will not rev up. This I know from experience,from the very 1st GX carb I worked on.