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Discussion Starter #1 (Edited)
Non-Adjustable Carb Too Lean - Toro 5/21
Tecumseh HS50 67259J
Carb 640084B

I have been off the forum for about a year due to health issues. I am now finishing off some projects I had to abandon.
Wow... It's amazing how quickly I've forgotten the basics!!

The original adjustable carburetor was not running properly even after an ultrasound clean.
I remember that it would start (during summer-time testing) but then stall again soon after starting.
Instead of spending hours fiddling and re-cleaning it... I decided to just buy a new carb.

So... I just fitted a BRAND NEW non-adjustable carb. However, it will only run on full choke. It shouldn't need to be cleaned because it's brand new.

I guess (in theory) the new carb could have some dirt left in it from the manufacturing process... but I'm guessing that's unlikely.
I checked for vacuum leaks by spraying carb fluid round the carb-to-manifold gasket.
Nothing obvious showed up. Everything is tight and snug. The gasket is new.

So unless I'm missing something obvious, because this is non-adjustable, I'm pretty much toast right?

So now I'm thinking of getting a THIRD carburetor... but I'll make sure I get an ADJUSTABLE carb this time.
Before doing that, I thought I'd see if anyone can think of anything worth trying that I've forgotten (while I've been out of action).

Any thoughts? Or do you agree that a third carb is the way to go?
 

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Drop the bowl and take a quick look, I guess. If anything can be unscrewed and looked at, do that, too. And make sure your own fuel and delivery system is pristine. That's all I can think of. Not much help.
 

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Discussion Starter #3
Yep... I need to eliminate any junk left in there by the (probably Chinese) manufacturer... I also need to eliminate any possibility of junk that came in immediately from the tank.
I'll flush the tank and the gas supply lines (again) and take a quick peek inside the carb (nothing to lose). I've never looked inside a non-adjustable carb.
This is the first (and LAST) fixed jet carb I've ever bought. I took a gamble... it doesn't look like it paid off too well.
 

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Discussion Starter #4 (Edited)
Oh well... I found another old carburetor (adjustable) and tried that instead. Works like a champ.
My conclusion..

AVOID BUYING NON-ADJUSTABLE CARBS if at all possible.

If they work... you got lucky... if they don't... there's nothing you can do except trying to randomly drill out the jets until it kinda-sorta-works-maybe.

Come to think of it.... there's no "one-size-fits-all" jet setting that works optimally (if at all) for ALL altitudes, ALL temperatures and ALL Weather Systems.
If you are lucky, your non-adjustable carb might be set correctly for Sea Level.. but that might not be good enough for 10,000 feet in the Rockies.
In my case, I don't think this brand new non-adjustable carb would work well at ANY altitude.

Google "Carburettor Altitude Mixture" to see why there's no one-size-fits-all solution. But then again... this is "just" a snowblower not an aircraft.
 

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A lotta Generator manufacturers claim in their sales blurb that they will NOT work above 3,000 feet. Some will change the carb, but most just don't bother. Seems like a niche market for real small superchargers.
 

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Discussion Starter #6 (Edited)
Yep... some(many? most?) carburetor manufacturers have "High Altitude Jet Kits" to try to take care of the reduced air density.
Even "disposable" engines (like Predators) talk about that in their owner's manual.
The "Big Box" companies aren't too helpful and just want to move inventory.
In my experience, their sales people don't even know about the issue.
So once again I'd say NEVER BUY A FIXED-JET CARBURETOR.. especially if you live in (say) Colorado.
If you buy a product that comes with a fixed-carburetor.... expect to be unhappy.

BTW. Something like 85% to 90% of the US population lives at or below 3000'.
So a carb adjusted for Sea Level may work for 90% of the population (maybe).
I suppose that's why the manufacturers can cut costs and sometimes get away with it.
They save 10 cents on an adjustable jet..... Is it worth it?..... I don't think so.

Given that I knew all this... I'm annoyed (with myself) for even thinking about risking a cheap fixed-jet carburetor.
Once bitten twice shy!
 

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I ALWAYS buy adjustable carbs and find them for the same prices as the fixed jet carbs. Glad you got it all sorted out.
 

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any time I have seen a thread like this ( only runs on choke or partial choke ) it usually mean one or both jets are partially clogged.

i usually clean the idle jet and then drop the bowl and spray carb cleaner up the pick up tube . sometimes unscrew the main jet out and clean it or run a wire thru the holes in the tube.

then it runs as it should.
 

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Discussion Starter #10 (Edited)
any time I have seen a thread like this ( only runs on choke or partial choke ) it usually mean one or both jets are partially clogged.

i usually clean the idle jet and then drop the bowl and spray carb cleaner up the pick up tube . sometimes unscrew the main jet out and clean it or run a wire thru the holes in the tube.

then it runs as it should.
Thanks for your suggestion. (BTW this is a brand-new carb so dismantling and cleaning really should not be necessary... I would have to be desperate to go there.... I just went with a third carb)

In my experience..
Cleaning the idle jet can be the silver bullet when your engine is "hunting". I've never really understood WHY that works.
Cleaning the main jet can be a silver bullet when things are "too lean"
Stopping the vacuum leak (ie air leak) is an alternate thing to check when things are "too lean"

So that brings me to another problem with these fixed carburetors..
The idle jet is no longer an adjustable screw-in jet... it's all hidden behind what looks like a fixed plug and I'm not even sure if you can remove them and put them back safely.
So that makes it tricky to clean out the idle even if you wanted to.
Maybe I'm mistaken and maybe you can safely pull them out and push them back in. I dunno... it sure looks "fixed" to me.... there's nothing to unscrew... just a black plug.

However, NONE OF THE ABOVE can save you if you have a high-altitude tuning issue. All you can do there is re-bore the jet. right?
 

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Thanks for your suggestion. (BTW this is a brand-new carb so dismantling and cleaning really should not be necessary... I would have to be desperate to go there.... I just went with a third carb)

In my experience..
Cleaning the idle jet can be the silver bullet when your engine is "hunting". I've never really understood WHY that works.
Cleaning the main jet can be a silver bullet when things are "too lean"
Stopping the vacuum leak (ie air leak) is an alternate thing to check when things are "too lean"

So that brings me to another problem with these fixed carburetors..
The idle jet is no longer an adjustable screw-in jet... it's all hidden behind what looks like a fixed plug and I'm not even sure if you can remove them and put them back safely.
So that makes it tricky to clean out the idle even if you wanted to.
Maybe I'm mistaken and maybe you can safely pull them out and push them back in. I dunno... it sure looks "fixed" to me.... there's nothing to unscrew... just a black plug.

However, NONE OF THE ABOVE can save you if you have a high-altitude tuning issue. All you can do there is re-bore the jet. right?
a lot of good info. you know more than I do. The prices of carbs are so low it is probably just better to replace than take the time to dismantle and rebuild . Your time is worth something.

I have the time , being retired, and just like to tinker so I'll do it since it is original equipment ( Honda ) and the cheap carbs appear to be just that ......cheap.

I did buy one on ebay for 12 dollars in change for a hs 50 or 624 and a couple other models but it is not that good. I can use it for parts.

Instead I bought a parts HS50 for 50 bucks and it has paid for itself many time over. already used carb, a cable, some handlebar parts, muffler , and other odds and ends, hardware etc.

so keep posting. have already learned from your posts and that's one of the reasons I come here and became a lifetime member.

thanks.
 

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That black plug is just a plastic cover, you can pry itoff with a small flat hear screwdriver then you can unscrew the jet for cleaning
 

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Discussion Starter #14
That black plug is just a plastic cover, you can pry itoff with a small flat hear screwdriver then you can unscrew the jet for cleaning
Good to know.. thanks... I wasn't sure about that...I just didn't want to risk it.

I had no real reason to get to the idle jet anyway... it's a NEW carb for goodness sake.

My problem needed me to be able to adjust the main jet... but that's not possible and I don't want to try to drill it wider.
The replacement ADJUSTABLE carb works just fine at this altitude (Mile High City) and I expect it would also work at 10,000 feet (in the Mountains).
 
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