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I will add in here..as a comparison...from the Ariens 306cc I found a 102 jet in the carb, which equates to .041 hole.. It had a slight misfire-fart at full throttle at 40f no load.

I went to a 0.042 hole size....which equates to around 105 ish....and its smooth as glass @3820 rpm.

kinda surprised at the jet size, when I read how the Hondas are quite a bit less.

clone carb jets are the same as Honda jets, in case anyone is wondering..at least what I have dealt with. Hope this helps someone.
 

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I opened it up to .041 and it’s a completely different machine. It is exactly what it needs. I said it was lazy now it’s a beast, open it up you will not be disappointed. You will not even recognize it. You guys getting the picture here. Lol

I will run it this way for a bit but may go to .043 worse case scenario is I buy a new jet and go back to .041 but I have a feeling it wants it.
Not only should you judge it by your perception of increased power and smoothness but also by the color of the spark plug. if the mixture is too rich it will start to look too black and sooty. Most have an opinoion of running an air cooled engine slightly rich because it runs cooler.
 

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Help at elevation
[snip]
I appreciate any input others may have at altitude
Yes, I would think a #78 (or larger) is the right direction if a #75 was bogging and a #72 is worse. Maybe try first a #78 & then a #80 if needed?
I picked up both a #78 and an #80 and installed the #78 tonight to start with.
I moved from a #75 to a #78 on my HSS724 just recently and it runs better, but I am at 200'.
I would be very interested in your results at #78 at your altitude. I am tempted to try the #80.
I just installed the #78 tonight and I cannot get over the difference in the way the engine sounds coming from the #72 honda installed. I didn't have any snow to clear, but the motor sounds like I went from 2hp to 50hp. I joke, but the machine sounds like it's now awake and alive at idle. I ran the auger with the throttle on high and I'm blown away. I'm actually anticipating the next snow (maybe tuesday) so I can actually test it under load.

I also picked up an impeller kit and installed that as well. I hope it'll help with discharging wet slop and slush on warmer days.

I'll update more when we have our next snow.
 

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I anticipate you will find quite a difference with the combined jet upgrade and the impeller kit.

As noted above, I bumped up to the #78 from a #75, but I am at sea level. If a #78 is working well for you a 6150', I am thinking I need to try a #80. Then figure out the jet on my HS720.

Please do update us. Perhaps even a snow throwing video. We like pictures (video even more).
 

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I think you got that backwards.

At elevation, you need a leaner jet due to less oxygen or..less air density.
it had a factory #75 in it, and then honda put a #72 in it due to my elevation. It ran worse when they changed it. I could honestly clear maybe 2-3" of snow depth at roughly up to 75% of full walking speed adjustment before it would want to bog down.
 

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it had a factory #75 in it, and then honda put a #72 in it due to my elevation. It ran worse when they changed it. I could honestly clear maybe 2-3" of snow depth at roughly up to 75% of full walking speed adjustment before it would want to bog down.
you misunderstood my point.

I am not saying it was jetted correct for elevation, only that engines require less fuel in elevation.

im not saying any engine is optimized for power from the factory.
 

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I say this a lot:

Start with the low side jet get a decent clean idle then move onto the high side.
The high side does not flow fuel at low speeds ( to any great degree )
The low side does flow enough fuel at high speed to make jetting peculiar shall we say...

So get low side first them tune the high for proper operation.
There are two styles of clone jet that are not interchangeable.
I bring this up often too. ( make sure your sets match or you get crazy results ).

Chinese jets and carbs tend to flow less well than OEM Japanese parts.
Do not think you can compare one to another all the time.
Differences in machining and finish make a huge difference in flow.

This tool really works.
 

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I'm at 9600 feet. My 1332 came with a 102 jet and 2.5 turns out of the pilot. My plug showed a rich condition so I jetted down to a 100 jet and left the pilot alone. Seems to do OK.

Snow Slope Plant Tree Mountain
 

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If your low side is lean ( and it probably is ) and your high side is lean ( and you have been working at that ) then adjusting the high side only will cause a miss match in the fuel curve at certain RPM ranges.
It might not bother you if you are running full out all the time.
It might manifest as slightly rich at 1/2 to 3/4 throttle but be just fine at full speed full power.

The air screw on these Chinese engines are almost useless.
All they can do is let a little more air into lean things further.
I never came across a clone with enough fuel at low side.

Its an EPA thing.
For best performance you want a little excess fuel on the low side for decent throttle response.
EPA has said they want the carbs set to best fuel mixture for operation.

All kinds of things done in the name of clean.
If you remember back to the cars of the 70s you will get that same feeling about today's engines.
For the same reasons....

Timing could be advanced a little...
But its not because of NOX limits
Mixtures are as lean as possible to reduce CO and HC.
This leads to a loss of power and sometimes sluggish response to the governor and hunting
 

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So the stock jet on a new GX390 snowblower is #102.
What were they using on older GX390 equipped blowers before they went too lean?



On a side note, I've seen a lot of mention of drilling jets.
I wouldn't even consider it as drills do not produce clean or round holes, for that you need a reamer and it really can't be done by hand as you want to ream perfectly straight. If you look at a drilled hole closely, it's pretty much trashed for anything that needs precision like a jet.

I'd always recommend buying properly sized jets.
yup. this thread has caused more problems than it has solved.

people drilling out jets, trying to do it themselves with the wrong size screwdrivers, damaging brass jets, leaking carbs , destroying carbs ,installing the wrong jet ..........

most of it depends on elevation. or on the new Honda's a lean jet.

Have a shop do it for a couple bucks.
 

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people drilling out jets, trying to do it themselves with the wrong size screwdrivers, damaging brass jets, leaking carbs , destroying carbs ,installing the wrong jet ..........
The learning curve is steep.
Maybe the best advice is not to do it at all.
Take it to the dealer...

Buy some jet blocks and prescision tools for a single time job is more expensive than paying someone to do it for you.
You can open up a jet one size or two with a pin vice but you need to be careful.
Surface finish effects flow as said before. ( if you have a prescision drill press hold the jet in the chuck and hold the bit in a squaured up machinist vice, you can make a very nice straight clean hole like that )

Sometimes a professional is not much help, and maybeeven gives you poor advice.
This lady is going to show you know how to work on a Walbro carb...
She does not have a pop off gauge or shims and springs.
No idea what to set up the carb before you install and try to use it.
I wonder how many followers she has?

 

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I am not going to watch that video. It takes a lot of skill and knowledge to optimize the fixed jet carbs. I will just add, adjustable main jet carbs solve most of these issues.
 

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The learning curve is steep.
Not really. The info in this thread and in the Repository is all you need to know to re-jet a Honda HSS carburetor in minutes. This video is particularly helpful:
 

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Ya your right keep doing what your doing.

If the low side jet, the E-tube and air screw did nothing why did they bother to design these parts into the carb.
Other people make simple cave man carbs that just used one jet?

Why bother with a low side at all if it does nothing.
 

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Ya your right keep doing what your doing.

If the low side jet, the E-tube and air screw did nothing why did they bother to design these parts into the carb.
Other people make simple cave man carbs that just used one jet?

Why bother with a low side at all if it does nothing.
They do a lot.
You're ignoring the fact these are already running engines that come jetted from the factory.

A slightly richer main jet could very likely be all they need. If even that.


You're talking like guys are mounting an aftermarket carb on a modified engine. They're not.
 

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They do a lot.
You're ignoring the fact these are already running engines that come jetted from the factory.

A slightly richer main jet could very likely be all they need. If even that.


You're talking like guys are mounting an aftermarket carb on a modified engine. They're not.
I struck some kind of nerve here and no one wants to believe me when I explain the low side effects the fuel ratio at all RPM and load ranges.
Its always contributing fuel!
Its a more precise way to set the carb up if you start with the low side.
You might not need as large a jet for the high side and if you want to tinker.
Sometimes an E-tube will change will put enough extra vac on the main jet to flow the extra fuel you need for both top end and mid range.

Just adding a bigger main only puts more fuel at the top.
at lower flow level there may now be an excess of fuel and it does not help at lower flow level at all.
I don't understand why there is so much resistance to the idea of more than one thing to adjust.
A lot of people have spent a lot of time on dyno and track learning this.

A lot more people are perfectly happy to let an engine spit and hunt because its too lean than do something about it.

Just try it....
Its easy to say no not interested.
Its not difficult to buy some jets and tinker and learn how the fuel flows in these carbs and make it perfect.
If all you want is good enough thats fine I get it....
But try these tips it won't harm anything and you might find you are happier than you were before.

Lots of people tinker for good reasons...
I knew EC Birt ( rip died on an operating table during back surgery, what a loss he was my mentor )
He special ordered these 304 bodies with only pilot holes drilled so we could literally make them do what ever we wanted.
They will not work until you start drilling and you better know what you are doing because its a lot harder to make holes smaller than bigger.
Your average shade tree mechanic will never deal with parts like these.
But you can learn so much about fuel flow by building your own stuff, experimenting and tuning.
 

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no one wants to believe me when I explain the low side effects the fuel ratio at all RPM and load ranges.
Actually, we all know that very well. You do understand that this is a Honda thread, right? The carburetors have a pilot jet that can be changed out, but usually doesn't need to be; it has an adjustable pilot jet needle screw. For example, when Honda upped the HSS1332 GX390's stock main jet from #102 to #110, they also changed the Pilot Jet Screw position from 2 turns out to only 1-1/4 turns out to compensate.
 

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Actually, we all know that very well. You do understand that this is a Honda thread, right?
Yes I was under the impression Honda engines also followed the normal laws of physics.

Done here...

Just for laughs can you tell me what that screw does?
Let me be very specific in my question.
What does turning it in do?
 
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