I probably should've posted this in a different section......

 

i forget where ive seen the info.. i think it was on some go-kart moding site.. but theres some info out there pertainning to what your after.. i wish i could rememebr and re-track it down myself.. as i think a simillar couse of action would be good for my engine too lol

 

EC Adjustable Gas Main Jet Kit for Honda GX390, Predator 420 & Clone Stock Carburetors

www.eccarburetors.com

 

That doesn't help me with the idle mixture?

 

Poke around the ARC website.

DJ-1241R Ruixing Low RPM Jet

low speed jet gx160 gx200 clone Ruing ruixing ruxing predator

www.arcracing.com

 

I am pretty sure its a glued/pressed cap that can be removed.

Pretty sure....

 

mine wasnt a cap

 

Part throttle .....remove the plastic philips head screw on side of carb.....pull out/pry out that plastic jet assembly......might be dirty-gunked...

sorry about the exact names of it...but I hope you know what im talking about.

 

 

whats modified? cam? head work?

they do sell diff pilot jet sizes.

also there is an adjust screw on most carbs....but ive Never needed any of that....

 

whats modified? cam? head work?

they do sell diff pilot jet sizes.

also there is an adjust screw on most carbs....but ive Never needed any of that....

Ok..
Very barely, hardly modified.
It's a 2022 EPA compliant summer engine with the air filter and spark arrestor removed.

With the 0.043 main jet (original was .0393), I think it's doing good under load but with no load it wants a hair more fuel. So when it cracks the throttle open sometimes it gets a hint of hesitation. Once it's under load it's good and remains good. I thought about reaming the idle jet some, but I have a feeling I'm going to remove too much no matter how careful I am.

 

i wouldnt worry too much on idle....as long as it holds the idle.....

its amost important at full throttle under load. if not under load, you cant tell didlesquat.

 

there is a screw on the carb--that will be hidden by a plug to keep you out of it.......
if you cant live without a smoother idle....try to find it, be real careful prying it off.. and then youll have a touch more adj.

im not looking for perfection on the snowblower at idle...its under load where it needs to be "safe". nobody will know their AF ratio unless they put a o2 sensor on it....Under Load to properly tune....and its kinda ridiculous.

but some machines might be too lean...add 1 jet at a time. I know there is a guy who did a vid series on jets on his 390 honda.....but just like a dyno tune, you have to be under load to see what the engine needs.......12.3 to 13.3 to 1 is the good area. keep in mind its a single cyl...


if it sounds like this..your good..lol...... EATS like a college football player..lol

 

View attachment 206339


I finally got some time to do an oil change and mess around a little more and as I thought it's idling a bit lean. Confirmed by closing choke a hair made it run a little faster.

I'm running a .043 main jet and removed the air filter, but have no way to change the idle mixture. It runs good under load but no load and idle is a hair lean.

Is there an easy way to change whatever this is or, are there known aftermarket carbs that run good and have an adjustable idle mixture? Is that a cap glued in? Is a screw that's broke off and glued?


@tabora

Leave it alone. If running too lean change the main jet. idle is no big deal. Who idles a snowblower while working it?
If it works great under load then leave it alone.
If you don't know what you are doing you are gonna screw it up even more.
See it all the time.

 

Leave it alone. If running too lean change the main jet.

But...it's not running too lean under load?

I mean I get it.
Everyone's saying "It's good enough leave it alone"

I get it.

 

I know the 254cc B&S is lean as all heck on my Ariens 28".

 

you know what that needs?

420cc clone. or a 389cc honda.

 

I mean I get it.
Everyone's saying "It's good enough leave it alone"

It's your machine and you have to use it... If a rough idle annoys you, change the pilot jet.

There does seem to be a group of folks that hold themselves as the Central Committee of what you can and can't do to your own machine.

And why not go all-in with a intake adaptor and pod air filter? That should get the Church Lady characters abuzz.

 

It's far from a rough idle. That I wouldn't tolerate at all.

This is the only video I have and that's not really an idle, but it's "slower" and unloaded. Also still cold at this point. Well, cool, it's kept in a somewhat warm crawlspace.

It's not a rough idle, it just wants a little more fuel when not under load, and perhaps a next size smaller jet for the main jet, maybe not. But like I said, I think it's so little I doubt I could ream the pilot jet that little.

 

So wait,
Do the pilot jets always have a number stamped / molded into the top of them?
And where can other sizes be bought?

 

It's not a rough idle, it just wants a little more fuel when not under load, and perhaps a
next size smaller jet for the main jet, maybe not. But like I said, I think it's so little I doubt
I could ream the pilot jet that little.

Once off idle, the pilot jet has no bearing on the fuel mixture. Assuming all other parameters are in-tune and functioning correctly.

Street motorcycles usually have three fixed jets -- idle/pilot-or-mid-range/main and then a tapered needle which allows the main jet to come online gradually though the upper RPM range. Although they overlap a little, once beyond their fuel delivery upper limits, they effectively bow out of the equation.

A long while back we discussed your leaking adjustable needle valve for the main. Did you remove that modification?

 

Yes, the night I tried it actually.
I'm running an .043 jet. OEM was a 101 which i think is .0393.

I could swear the pilot jet was still in use at 3600 RPM no load. Are you 100% sure it's not? It always seemed like it was on my adjustable Tecumseh.

 

A long while back we discussed your leaking adjustable needle valve for the main.
Did you remove that modification?

Actually, I'm about ready to head out into the garage and install my eBay copy of the adjustable needle main jet. Hopefully, mine won't leak.

 

I could swear the pilot jet was still in use at 3600 RPM no load. Are you 100%
sure it's not? It always seemed like it was on my adjustable Tecumseh.

It's still delivering fuel. But its percentage contribution is so small it shouldn't matter. Once again, assuming the other players in the equation are up to snuff.

 

I don't know......
Wouldn't the engine, in theory only use 50% more fuel at 3600 unloaded than 1800 unloaded?

 

I don't know......
Wouldn't the engine, in theory only use 50% more fuel at 3600 unloaded than 1800 unloaded?

Welcome to the painstakingly arduous task of dialing in carb settings for perfect idle, acceleration, drivability, and top-end performance...

If it was easy, every motorcycle squid on a Summer's Friday and Saturday night wouldn't have a popping and backfiring issue on deceleration from light speed.

 

Not true, popping on decel is normal for a properly tuned circuit, especially on low restriction exhaust systems. The fuelie machines can easily tune it out if their software allows for it, but on a carb it requires an overly fat idle mixture to eliminate decel popping/cackles

 

Not true, popping on decel is normal for a properly tuned circuit, especially
on low restriction exhaust systems. The fuelie machines can easily tune it
out if their software allows for it, but on a carb it requires an overly fat idle
mixture to eliminate decel popping/cackles

I don't know how many times I have to say this on various personal preference topics, but here it goes again... If blubbering, burbling, backfires, and popping on decel float your boat, have at it! If jumping car suspensions are your thing, knock it out of the park.

But, my personal preference is to have my street vehicles perform at their maximum, be polite, and well groomed while among other road users and those living in the community I'm traveling through.

 

That “fix” is to enrichen the idle circuit beyond ideal. Like you say, to each their own but decel popping on easy breathing (read: short exhausts like OPE) is not a sign of mis tune, it’s the opposite. I’d rather have my idle settings right versus stopping having some harmless cackles on throttling down.

There are a ton of resources on the net that describe this phenomenon.

 

There are a ton of resources on the net that describe this phenomenon.

And no doubt, I've visited a few since my vehicles don't fart and burp through town.

 

I have a feeling your main one most certainly does burp and fart through town. Literally.

The TBI 305 or 350 isn't carbureted. L03 or L05 if memory serves.

 

I have a feeling your main one most certainly does burp and fart through town. Literally.

Referencing the dozens of street and dirt bikes that have passed through my garage over the decades. A quiet street-legal dirt bike is worth its weight in gold since the machines are already looked upon unfavorably by others in the forest-going public.

 

Actually, I'm about ready to head out into the garage and install my eBay copy of the
adjustable needle main jet. Hopefully, mine won't leak.

Adjustable needle main jet installed. The stock main jet is #82 for my 301cc 8HP Predator engine. The replacement jet has had its number stamp sanded/ground off. Most likely, it has been drilled out to a larger diameter allowing the needle to do the metering.

On my machine, I currently have the needle opened 1.25 turns out/open when loaded with the auger/impeller spinning. However, until I get a good dumping of snow to load the engine fully, this is just a starting point.

Chris, I noticed the external arrangement of the needle valve setup. Starting from the bottom, it's the hex screw/needle body, spring, washer, and o-ring. There's not much tension provided by the spring. Maybe preload the spring with a stack of 3 or 4 washers to increase?

Next time I have the desktop lathe out, I will cut a small aluminum spacer cylinder to create a bit more preload on that spring.

 

Yours looks identical to the one I have.
How exactly is an O-ring with almost no pressure on it supposed to seal against the threads on a screw?
Because if you look, that's exactly what they did.

The one on the Tecumseh carb I have seals against a nice smooth shoulder.

 

Yours looks identical to the one I have.
How exactly is an O-ring with almost no pressure on it supposed to seal against the threads on a screw?
Because if you look, that's exactly what they did.

The one on the Tecumseh carb I have seals against a nice smooth shoulder.

Some dude in his basement puttin' together kits from readily available off-the-shelf components.

The aftermarket is starting to fill in the vacuum, however:

Adjustable Main Jet Kit for Gas Tuned GX200 Clone & Predator 212 Carburetors

www.eccarburetors.com

 

Who is doing it and where isn't really the point.
The point was, it's going to leak. That's why mine was removed and installed in the cabinet for now but it's likely going to go in the trash.

The link you posted looks much better though.

 

Moderator?! Oh, Moderator!
Some nasty bike riders have putted down our snow-lined avenue.
It does explain some things, though.