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Discussion Starter #1
Cub Cadet (24 inch 208cc engine) comes with a Carburetor as shown in the attached picture. Snow Blower Carburetor for HUAYI 170SA
To run the snowblower smoothly I have to keep about Choke on about 20%. I can not turn off the choke completely.
The carb is new (after market). I also tried to replace the Main Jet and the Emulsion tube from another similar machine which runs 100% fine (no choke required on that machine to run).But that did not help either. The jet and emulsion tube have been thoroughly cleaned.

Is there any settings on the carb which will fix the issue? Do I have to adjust the Idle jet or the Idle screw as shown in the attached picture? If yes, then do I turn the screw clockwise or counter clockwise?
 

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Yes you should remove the idle jet and clean it out. At the same time clean out the passage way in the carb. Using your solvent of choice and then compressed air. Using a small wire (in the shape of an L) make sure the small jets in the throat are open. This will probably fix the surging.
If not......
There was a recent post by a member who regularly finds that opening up the orifice on the idle jet has solved surging on carbs of this type when a good cleaning does not solve it. If you have some micro drills(HF has them) you can try to open it to the next size up. Open up only by .002 to .003 is a good step size to go at it. It is trial and error.
The idle screw won't solve rough running with out the choke on.
Good luck
 
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Discussion Starter #3
Yes you should remove the idle jet and clean it out. At the same time clean out the passage way in the carb. Using your solvent of choice and then compressed air. Using a small wire (in the shape of an L) make sure the small jets in the throat are open. This will probably fix the surging.
If not......
There was a recent post by a member who regularly finds that opening up the orifice on the idle jet has solved surging on carbs of this type when a good cleaning does not solve it. If you have some micro drills(HF has them) you can try to open it to the next size up. Open up only by .002 to .003 is a good step size to go at it. It is trial and error.
The idle screw won't solve rough running with out the choke on.
Good luck
Thanks Toro. I mentioned in my post that the carb is new (after market). Should I still clean the idle jet or try to open up using micro drill?
 

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Yes definitely clean the new carburetor before you install it or you will have the same problem as you did with the old one 'Surging'.
Check your 'Float Level' and adjust if you can if that is out of spec.
 

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Clean it before you open it up and see what happens. If you open it up and that is not needed you can end up running too rich. You will know this by having a black and sooty spark plug. I am not sure if the float is adjustable on your unit. It is a good idea to check it as suggested by ST100A. Usually if held up side down it should seal level or slightly down from the bowl sealing edge. I like to see it slightly down as it lets a bit more gas in to the bowl.
 
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Discussion Starter #6
Check your 'Float Level' and adjust if you can if that is out of spec.
Here is the photo of its older (original OEM) carb. It was too rusty and was leaking from the needle seed so I end up replacing it with an after market carb.
You can see the float here and let me know if this is adjustable or not. If it can be adjusted then please let me know steps of how to do adjust it.

174557
 

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that one is not adjustable, if it was you would see a metal tang that gets bent to set the level,

the issue your describing sounds like a lean carb, wait a bit for one of the other guys to help
 

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Those 'Huayi' carburetors were very poor to begin with and not much could be done to help them.
Down at the bottom where the bolt that holds the fuel bowl on, you have to make sure there is either a little groove space for fuel to enter to get to the main jet, or on the sides of the tube that holds the main jet sometimes there is a small hole that lets fuel enter from the bowl to the main jet. That hole has to be clear and open enough for fuel to get into the passageway.
Sometimes those holes are blocked by the main jet because of where they are drilled at, a manufacturing defect which is extremely common with them.
The entire design is a very bad design and they have absolutely no quality control what-so-ever with their manufacturing to ever see they have a problem with them.
They used a couple of different designs on them because most of them did not work satisfactorily, so you never know what one you are getting because they were so mixed up when they were made in the beginning, and they still never straightened them out yet.
You could buy 100 replacement ones and maybe 15 to 20 of them might work good, the rest are junk with too many failures in them.
'MTD/Cub Cadet' products are very well known for having many 'Bugs' and quality issues with their products over the past few years unfortunately, and by trying to save money they went with the cheapest engines they could be supplied with to try and make a profit for the company, and it really started to 'Back-fire' on them.
The only way to really be able to make them more reliable again would be to 'Re-Power' your machine with an engine of a different manufacturer and stay away from the Cub Cadet power plants.
You would want to 'Re-Power' it with a more expensive engine manufactured by a 'Well Known' supplier who has a good quality reputation and a good 'Support' foundation for service and parts.
Unfortunately most all engines are made in China today, and most of them are the ones to stay away from, but your better 'Supported' engine manufacturers are companies like Briggs&Stratton and Honda if you can afford them, but there quality, support, and parts availability is still there yet.
Be very careful of those 'Discount' engines and a lot of the newer popular discount engines that are becoming popular today because they do not have the long standing reputations built up yet, and their 'Support' isn't quite there yet for parts and service so you could buy one cheap and be out of luck when it fails.
 

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Many of the aftermarket (and new OEM) carburetors seem like they are set lean. If the engine will run on 20% choke +/-, I'd do it as a short term measure and then consider a main jet reaming with a set of micro drills for a longer term fix.
 

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Or tuned for summer . . . cold, denser winter air has more O2, and will also cause a summer tune to be too lean . . . not sure if the offshore junk vendors consider winter . . .
 

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Discussion Starter #11
I'd do it as a short term measure and then consider a main jet reaming with a set of micro drills for a longer term fix.
Should I ream just the main jet or do I also have to ream the Emulsion tube? What size of bit should I use?
 

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IF cleaning does not solve your problem start by opening the main jet a few thousanths of an inch. Don't worry about the emulsion tube.
 

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Discussion Starter #13
opening up the orifice on the idle jet has solved surging on carbs of this type when a good cleaning does not solve it. If you have some micro drills(HF has them) you can try to open it to the next size up. Open up only by .002 to .003 is a good step size to go at it.
I am confused now. Do I have to open up the Idle jet or the Main Jet?
 

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Be careful when you start 'Reaming' or 'Drilling' out a Jet, any jet.
Most jets have a built in 'Venturi' in them and if you drill/ream it out, you will remove the venturi and that can cause some problems and make it worse than better.
Most of your American made carburetors and some Japanese made units have different size factory original jets available like Briggs, Tecumseh, Kohler, Walbro, Honda, Yamaha, Suzuki, Subaru-Robin for instance.
You are better to replace the jet with a Larger one than to 'Modify it if possible.
Most of your discount Chinese made motors carburetors don't have optional sized jets available for them.
When you remove the 'Venturi' in a jet, it will make the fuel 'Piss' up through the emulsion tube and into the 'Venturi' of the carburetor in large fuel droplets, then it wont atomize well and mix with the incoming air before it enters the combustion chamber, and will become harder to ignite and harder to burn off completely creating a loss of power and a 'Richness' in the exhaust emissions.
The 'Venturi' effect in the jet itself causes the fuel to actually 'Speed itself up' when passing through the jet and mix better with the air that enters through the tiny 'Air Bleed' holes drilled into the emulsion tube before it enters the 'Venturi' or 'Throat' of the carburetor. That way it becomes a better 'Mist' with much finer fuel droplets and mixes with incoming air much better so it can be ignited easier and burn much better and have a more complete burn in the combustion chamber before the exhaust valve opens to clear the spent mixture out of the cylinder, giving more power and better fuel mileage.
You want all of the fuel to burn cleanly and completely in the combustion chamber to produce the most power.
 

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I am confused now. Do I have to open up the Idle jet or the Main Jet?
Again if a thorough cleaning does not solve your surging you can open up the main jet like .002". See if that help. I know one member on here says to open the idle jet. I personally have never had any success with that. I do not doubt his success. The idle jet is a much smaller opening so a .002 inch increase is a much larger percentage. When you are at running speed (about 3600 rpm) the idle jet does not do much. You are surging is at high speed right?

If it does not work go another .002 larger. If you go too far it will run too rich. I my opinion slightly rich is ok...... I like to set engines up slightly rich. They run a bit cooler.

Right now your carb is junk, If this does not work, it is still junk. You can buy Honda main and idle jets at OMB Warehouse. They work in the Predator. I don't know if they will work in one of the MTD Powermore carbs. Maybe someone here can confirm this?

I am running my predator with a .032 main jet. Larger was too rich. Stock was .028 (i think). This is another option. More expensive but gives you a lot of flexability and ease. This way you can go backwards if you decide smaller was better.

Measure were your jet is now with your micro drills. You can get an idea of the range if not precise. See if you can go up in .002 increments to find the sweet spot.

Below is a jet kit as an example of what is out there. I think you can buy individual sizes as well. Check it out. I am sure there are other sources. Good luck

 

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Discussion Starter #16
You are surging is at high speed right?
Yes, the machine runs on 20% choke at the full speed

Again if a thorough cleaning does not solve your surging you can open up the main jet like .002".
The micro drill which I am going to buy has the following drill bit sizes:
Drill specifications (in mm): 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 2.0mm
Which one of these bits I should use?
 

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That set is probably like what I posted below. You need the pin vice to hold the drill bit. Then you can use the drill bit like a guage pin and determine what size jet hole is there now. You need to know this to establish a base line. Then go up in .002" increments. Be gentle as they are easy to break. Easy to loose too as they are very hard to hold. But they are magnetic so keep that in mind and use it to your advantage. Run it and see how it performs. Good Luck.

 

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Discussion Starter #18
An update from my initial post. The new after market carburetor which was running on 20% choke, is now able to run smooth when I completely turn off the choke. The issue is completely gone.
I have not done any adjustments or cleaning at all after my initial post. I always use fresh Premium gas (no more than 2 weeks old)
Just wondering what would have happened and have fixed the issue?
 

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Are you sure you did not add something to the gas that may have cleaned up any debris in the the ports? i.e. Seafoam, Gumout, mechanic in a bottle etc.
 

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Discussion Starter #20
Are you sure you did not add something to the gas that may have cleaned up any debris in the the ports? i.e. Seafoam, Gumout, mechanic in a bottle etc.
No I did not add anything to the gas for cleaning. I use straight Premium gas. The carb is brand new after market from Amazon.
 
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