honda gx 390 problem

[wisecobandit]

Ah this old chestnut. Theres a little passage which has a very narrow passageway thru it which chokes up on the gx160/200 carbs and causes this. Its a pilot jet.

There are 2 adjustment screws, ones a plastic tickover type screw and the other is a brass air/fuel screw.The plastic jet is behind the brass scew. With the carb off you will see some very small holes in the main bore of the carb which will be obvious when you look.

They need blowing out with carb cleaner, they block up causing the surging issue.

[wisecobandit]

This link will help. Its easier than me trying to explain. Have a look at the pilot.

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

[GardenKit]

Very well described Wisecobandit, and this is indeed the way to clean a small Honda carb that hunts on idle, but wont cure one that will only run on choke. That will be a main jet blockage.The Honda carb cleaning picks ( thin wires) help to shift stubborn solids from the pilot jet, or a good boil up in the US cleaner helps. Even then they dont always work and a new carb is required.

 

The carb in question on this thread was from a GX390, but a new carb has been ordered for that. The carb now current belongs to Colletti and is from a GX670 twin cylinder.

 

These are much more complex carbs with twin throats, one for each cylinder. They require more carefull cleaning. The pilot jets are sealed in the top cover under brass plugs which need to be drilled out to get access to the head of the jet so that they can be renoved for cleaning. All other jets are easy to see and remove, but dont try to remove the two mixing tubes with the little rubber caps, or try to remove the caps, unless you have replacements.

[Breezeblock]

the damn thing has now cured itself i had it running today i think a bit of fresh petrol and vibration from the grinder has loosened any thing that was in the carb so now it runs ok all that of course happened after i ordered carb off ebay:mad1:

[GardenKit]

the damn thing has now cured itself i had it running today i think a bit of fresh petrol and vibration from the grinder has loosened any thing that was in the carb so now it runs ok all that of course happened after i ordered carb off ebay:mad1:

Hahaha, thats 'sods law' breezeblock. It usually happens t'other way for me. Its OK when I service it but plays up when it get backs to the owner:laugh1:

[GardenKit]

Very well described Wisecobandit, and this is indeed the way to clean a small Honda carb that hunts on idle, but wont cure one that will only run on choke. That will be a main jet blockage.The Honda carb cleaning picks ( thin wires) help to shift stubborn solids from the pilot jet, or a good boil up in the US cleaner helps. Even then they dont always work and a new carb is required.

 

The carb in question on this thread was from a GX390, but a new carb has been ordered for that. The carb now current belongs to Colletti and is from a GX670 twin cylinder.

 

These are much more complex carbs with twin throats, one for each cylinder. They require more carefull cleaning. The pilot jets are sealed in the top cover under brass plugs which need to be drilled out to get access to the head of the jet so that they can be renoved for cleaning. All other jets are easy to see and remove, but dont try to remove the two mixing tubes with the little rubber caps, or try to remove the caps, unless you have replacements.

In the cold light of day I need to correct my quoted post, before someone else does:blushing:

 

The practice is right, the terminology wrong.

 

The pilot jets are of course easily unscrewed from the bottom of the float chamber. The things under the brass plugs are the pilot circuit mixture screws.

They do still need to be removed for a good cleaning.

The things I often refer to as mixing tubes, are in fact the main fuel nozzle.