Snowblower Carb...too Lean?

[tbm5690]

I have a Chonda 357cc engine on my snowblower. I bought it used last fall and noticed that with the choke fully open it stumbles a bit. The choke knob has 4 positions (let's say position 1 is closed and position 4 is full open), and if I keep it on position 3 it's smooth as butter. On full open it runs great with load and has no issues powering through snow...it only gets a bit rough when running at no load, regardless of throttle position. I expected a partially clogged jet so I replaced the carb entirely, and with the new carb it does the exact same thing. Fuel is good, tank is clean, so all good on that end of things. Is this worth pursuing a solution? I've also heard that some of these carbs just run lean as sized from the factory and the non-load run may be a bit rough, but as long as when running at load they are good there isn't anything to fix. Thoughts?

 

[Urshurak776]

You need a snow blower April 1st?

Only advice I can give is move! Yikes!

 

[Brian123]

I have a Chonda 357cc engine on my snowblower. I bought it used last fall and noticed that with the choke fully open it stumbles a bit. The choke knob has 4 positions (let's say position 1 is closed and position 4 is full open), and if I keep it on position 3 it's smooth as butter. On full open it runs great with load and has no issues powering through snow...it only gets a bit rough when running at no load, regardless of throttle position. I expected a partially clogged jet so I replaced the carb entirely, and with the new carb it does the exact same thing. Fuel is good, tank is clean, so all good on that end of things. Is this worth pursuing a solution? I've also heard that some of these carbs just run lean as sized from the factory and the non-load run may be a bit rough, but as long as when running at load they are good there isn't anything to fix. Thoughts?

So, when this Engine is running at full Load powering through the Snow it is fine?
So, when you are not blowing snow, and it is idling that is when you have your issues?
You might want to check everything going from the Choke Knob to the Carburetor.

 

[mk378]

Surging at no load is sometimes unavoidable. The general setup for "idle" is to hold the throttle plate all the way closed (against the stop screw) and adjust the stop screw and the idle mixture screw (if equipped, it will be in the side of the flange where the carb meets the intake) for a steady run.

 

[tbm5690]

So, when this Engine is running at full Load powering through the Snow it is fine?
So, when you are not blowing snow, and it is idling that is when you have your issues?
You might want to check everything going from the Choke Knob to the Carburetor.

Correct, full load no issues. Sitting there idling is the only time it does this, and only with the choke open (partially closed it smooths out, but then obviously doesn't have the same power under load. I went through everything when I installed the new carb...all looks good. Line is clear, tank is clean, gas is fresh. Choke knob works as intended.

 

[tbm5690]

Surging at no load is sometimes unavoidable. The general setup for "idle" is to hold the throttle plate all the way closed (against the stop screw) and adjust the stop screw and the idle mixture screw (if equipped, it will be in the side of the flange where the carb meets the intake) for a steady run.

That's what I'm thinking might be the case (unavoidable) considering both the old and new carb are the same. No idle mixture screw on this carb.

 

[TomYoung]

If the issue is a little stumbling at full choke, I think we can live with that.

 

[tbm5690]

You need a snow blower April 1st?

Only advice I can give is move! Yikes!

Some years...3-5 inches today/tomorrow. I like seasons and no palmetto bugs

 

[Brian123]

Correct, full load no issues. Sitting there idling is the only time it does this, and only with the choke open (partially closed it smooths out, but then obviously doesn't have the same power under load. I went through everything when I installed the new carb...all looks good. Line is clear, tank is clean, gas is fresh. Choke knob works as intended.

The next time you use this Snowblower do the choke thing and let it run for like 4 or 5 minutes and then do your snow blowing and if the same thing happens look for some kind of vacuum leak. The only other thing is maybe run some fuel cleaner.

 

[tnt_motorsports]

That's what I'm thinking might be the case (unavoidable) considering both the old and new carb are the same. No idle mixture screw on this carb.

FWIW, I think if the muffler is not glowing red and you don't have other signs of a problem then run it. You could up size the jet if you are worried about it.

 

[Analog-1]

You need a snow blower April 1st?

Ahh YES. There are plenty of states that get snow and ice anytime in April. Here in Michigan we are expecting snow and ice over night tonight, followed by severe thunderstorms tomorrow early afternoon and again in the evening.

 

[eljefino]

I repowered my old Toro with a Chonda about ten years back. It was a universal engine from HF and therefore:

-- had an air filter which I removed

-- was calibrated to run at room temperature

-- was calibrated to run on zero ethanol gas

-- was also calibrated lean.

I went up 2.5 jet sizes to fix this. Got a numbered drill bit set (60-80?) online for a few bucks. Came with an "Xacto knife" bit holder. The bits were tiny!

No more surging and man the thing powered through snow drifts at WOT as well. Highly recommend.

 

[BigCahuna]

It sounds to me that if it's running like you say, I would try to dose the fuel with carb cleaner, and let it run a tank thru it. If it starts to run smoother wide open, you know you did something. Cheapest, easiest way to remove gum and dirt.,,

 

[tbm5690]

The next time you use this Snowblower do the choke thing and let it run for like 4 or 5 minutes and then do your snow blowing and if the same thing happens look for some kind of vacuum leak. The only other thing is maybe run some fuel cleaner.

It still does it even after running through snow for 30 minutes plus. Vacuum leak where? The gaskets were replaced when I replaced the carb, and there is a breather line that goes from the head to the carb intake box and it is clear.

 

[tbm5690]

I went up 2.5 jet sizes to fix this. Got a numbered drill bit set (60-80?) online for a few bucks. Came with an "Xacto knife" bit holder. The bits were tiny!

No more surging and man the thing powered through snow drifts at WOT as well. Highly recommend.

Since I have the old jet still I may drill it out and replace it to see what happens.

It sounds to me that if it's running like you say, I would try to dose the fuel with carb cleaner, and let it run a tank thru it. If it starts to run smoother wide open, you know you did something. Cheapest, easiest way to remove gum and dirt.,,

Brand new carb, and fuel tank was gone through prior to me replacing the carb. So, no gum or dirt.

 

[repairman54]

I'd live with a no-load lean surge over being too rich myself. Until I needed something to mess with LOL.

 

[BigCahuna]

I'm sure the carb you replaced it with is used on other machines beside your snowblower. The main difference is the other machine more than likely also use an air filter. I haven't seen a snowblower with an air filter, so that might cause it to run a little leaner. Unless you try an add one, you might just have to live with the high speed lean condition.,,

 

[The_Eric]

Since I have the old jet still I may drill it out and replace it to see what happens.


Brand new carb, and fuel tank was gone through prior to me replacing the carb. So, no gum or dirt.

Sounds like you're a hair lean on the pilot only. I'd measure and go up 5% in diameter - probably .001" or .002"

I'm guessing there's no air filter on the snow blower? That or the fact that it's cold when you run it is probably the issue.

 

[grasscutter]

Is there a limiter cap on the idle mixture needle like this?

 

[tbm5690]

Sounds like you're a hair lean on the pilot only. I'd measure and go up 5% in diameter - probably .001" or .002"

I'm guessing there's no air filter on the snow blower? That or the fact that it's cold when you run it is probably the issue.

No filter, and it does it regardless of temp...I ran it late summer last year with the same issue.