Honda Idle Jet Size

[Merkava_4]

You see that Phillips head screw right next to the limiter cap? Down below that screw inside the passageway is an idle jet. I wish I knew what size it is because I need to enlarge it. The mower surges at idle right after the choke pulls off. I even bought the official Honda Jet cleaner. The idle jet takes the smallest jet cleaner wire in the kit and it's made for jet sizes #35 through #40. If you had to guess, what size would you say the idle jet is?

 

[Merkava_4]

Can one of you guys say something? Tell me to go to hell if you have to, but say something.

 

[redneckhillbilly]

is the choke opening up too soon?
does it clean up and run smooth after its ran for a while?
you sure the stack of gaskets behind the carb are installed properly and not leaking?

 

[Coupe]

Sounds as though the idle jet is still blocked but in saying that I would
strip the carby down and give it a real good clean and a blow out with
compressed air. Also check the governor spring has not been stretched
as this will cause them to surge in a big way. when you put revs on it does
it straighten it's self out.

 

[Merkava_4]

is the choke opening up too soon?
does it clean up and run smooth after its ran for a while?
you sure the stack of gaskets behind the carb are installed properly and not leaking?

I think the choke will stay on for 5 minutes or so. During that time, the engine runs beautifully. When choke goes off, the engine will start surging at fast idle. I call it fast idle because the engine doesn't go full speed until the blade is engaged. I can stand in front of the mower and watch the governor arm pulling on the carb butterfly. It's doing its job real good. This mower is only about two weeks old. I take very good care of it. It's only cut two yards so far. Each time after it's done cutting I flip the mower deck on its side and wash the mower deck out real good. I plan on having this mower a long time and I don't want any deck corrosion. I keep the mower as clean as when it was new.

The carb gaskets are installed correctly and today I was spraying carb cleaner where the carb meets the cylinder. I was hoping the engine would quit surging by sucking in some carb cleaner in around the gaskets. Nothing happens unless I deliberately spray the cleaner down the carb throat. The engine only uses 3 carb mounting gaskets. The engine has threaded studs for the carb. It only takes between 5 and 10 minutes to swap out the carb. The engine is a breeze to work on. Thanks for replying I appreciate it.

 

[Merkava_4]

Sounds as though the idle jet is still blocked but in saying that I would
strip the carby down and give it a real good clean and a blow out with
compressed air. Also check the governor spring has not been stretched
as this will cause them to surge in a big way. when you put revs on it does
it straighten it's self out.

I already poked the idle jet with the smallest wire in the Honda jet cleaning kit. The idle jet is somewhere between 0.35 and 0.40 millimeters. That's getting down to arm hair diameters. Everybody tells me to clean the carb real good which I did, but the carb was never dirty to begin with. I started it up and ran it before the mower ever set foot on any grass. It started surging literally right out of the box. And it even continues to surge with a different carburetor; that tells me there's a design problem. It'll cut the grass, but during that whole time it drives me insane with the idle surging. I'm going to put the mower in the shop tomorrow. I'm going to take it to a place that's been in business for over 40 years. What they'll probably do is enlarge the idle jet but just tell me they cleaned it.

 

[huskihl]

Have you tried using different Fuel? If your gas has any ethanol in it, the ethanol contains oxygen and that will lean your fuel mixture somewhat if you don’t have the ability to adjust for it

 

[nbbt]

It looks like your in Cali. Look up the carb specs for a non-west coast equivalent motor. It's a guarantee that the main jet is 1- 2 sizes to small.
I had a similar issue on a predator 6.5hp and enlarged the main jet (by 0.0025-0.0035" for that 6.5hp predator) and the lean surge was nearly eliminated when cold. When warm it ran very acceptable. As part 2 the hole in the throttle blade might need to be enlarged if it is still surging when under little load.

Your results may vary . . . Just observations from my experiences.

 

[EFSM]

Have you checked static governor adjustment? If this is a new mower, by all means have the dealer mess with it. That's what they're for, unless they're completely incompetent.

 

[Merkava_4]

Have you tried using different Fuel? If your gas has any ethanol in it, the ethanol contains oxygen and that will lean your fuel mixture somewhat if you don’t have the ability to adjust for it

I wish I could buy ethanol free fuel, but there is none in California. I get my 2-cycle fuel from a Sinclair station because I can have the pump shut off at exactly 2.501 gallons. The Honda has been running on car fuel which is Costco Kirkland 91 octane.

 

[Merkava_4]

It looks like your in Cali. Look up the carb specs for a non-west coast equivalent motor. It's a guarantee that the main jet is 1- 2 sizes to small.
I had a similar issue on a predator 6.5hp and enlarged the main jet (by 0.0025-0.0035" for that 6.5hp predator) and the lean surge was nearly eliminated when cold. When warm it ran very acceptable. As part 2 the hole in the throttle blade might need to be enlarged if it is still surging when under little load.

Your results may vary . . . Just observations from my experiences.

The engine doesn't run on the main jet at idle does it? At full throttle with the blade engaged, it runs fine.

 

[Merkava_4]

Have you checked static governor adjustment? If this is a new mower, by all means have the dealer mess with it. That's what they're for, unless they're completely incompetent.

I'm taking it to the dealer but it's on my dime. This is a big box store special, so taking it back for service is not an option.

I haven't checked the governor because the engine runs fine under load. It's really acting like an idle circuit problem.

 

[lwn9186]

Your carburetor diagram shows to have a mixture screw (4). Take the limiter off and turn out 1/4 of a turn and see if that helps.

 

[stretch5881]

Most small engines on push mowers surge when not under load. EPA requires lean running engines. As long as it runs fine when it's loaded, it's doing what it's designed to do.
An idle circuit works at low rpm, so I'm pretty sure yours does not have an idle jet.

 

[Merkava_4]

Your carburetor diagram shows to have a mixture screw (4). Take the limiter off and turn out 1/4 of a turn and see if that helps.

They got that thing setup to where if you try to remove the limiter cap, the mixture needle shears off.

 

[Merkava_4]

Most small engines on push mowers surge when not under load. EPA requires lean running engines. As long as it runs fine when it's loaded, it's doing what it's designed to do.
An idle circuit works at low rpm, so I'm pretty sure yours does not have an idle jet.

Down below that Phillips screw is tiny brass hole. I'm calling it an idle jet, but it may be something else.

 

[Wonkydonkey]

If you want to make some ethanol free fuel just so you can try to see if it makes a difference.

There’s plenty of vids out there on how to do it. Look At youtoob.
It’s as simple as add a known amount of water to the fuel and shake then let it settle out and pour off the ethanol free fuel of the top.

I’ve don’t it a few times, however I find it easier to add a bit of food colouring to the water before adding it to the fuel, it makes it easier to see when decanting.

 

[stretch5881]

Down below that Phillips screw is tiny brass hole. I'm calling it an idle jet, but it may be something else.

View attachment 447466

Pilot jet.

 

[stretch5881]

They got that thing setup to where if you try to remove the limiter cap, the mixture needle shears off.

A dremel makes short work of the tab on the limiter.

 

[Merkava_4]

A dremel makes short work of the tab on the limiter.

Oh I know that. I've got the Dremel and the cutoff wheel. The thought has crossed my mind.