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Discussion Starter #1
Hey everyone,

So I bought a used 2012 model 726 OE in pretty good shape (pics to come!), and when I disengage the auger, the engine has a tendency to backfire. It also happens when I shut off the snowblower - there's a final pop. Is this normal? I don't think it is, and if that's the case, what could it be?

Thanks in advance!
 

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usually means running lean, more air than fuel. when ur about to lower throttle put choke on the first indent and see what happens . clean the carb and/or use seafoam or similar
 

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Discussion Starter #4
Briggs lists the following as possible causes:
  1. Lowering engine speed too fast
  2. Gasoline, which contains higher blends of alcohol
  3. Carburetor adjustment set too lean
  4. Muffler construction can induce backfire
  5. Higher than normal engine temperatures
Number 1 isn't the case, because it happens without load.
Could be the type of gas. As I just got it, the PO might have used some funky gas.
Number 3 is a definite possibility.
Number 4 and 5 would surprise me.

Does anyone know the carb setting for this snowblower?
 

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there is probably no adjustment on the carb, the jets are fixed. if you can take it apart and clean it or at least try something like seafom to clean the carb
 

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my kohlers all do the same with stock settings, summer or winter, my personal fix has been to slowly lower the throttle down to idle than shut it down, seems to stop the lean backfire issue.
 

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Discussion Starter #7
So I ran it again tonight to see what the effects were, and sure enough the backfiring occurred, even with some load. The top rear of the muffler started to get a little red (is the common? I've only run it during the day, this was my first time running it at night). As for the Sea Foam, I've used it with cars but never a snowblower. Is the principle the same? Fill the tank with it?

Vinny, I forgot to check using the first indent of the choke. Good thing there is more snow in the forecast!

What would the danger be of running it lean? Burning a hole in the piston?
 

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Discussion Starter #8
When I put it on the first indent of the choke, there is a small reduction in the backfiring. On the second even more so. Lean would seem to be the issue. I'm gonna SeaFoam it today and see. Thanks.
 

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When I put it on the first indent of the choke, there is a small reduction in the backfiring. On the second even more so. Lean would seem to be the issue. I'm gonna SeaFoam it today and see. Thanks.
well u have a fuel issue, not enough getting mixed in w/air, or too much air getting into the intake pipe(between butterfly and engine intake hole).
u can spray carb cleaner on intake pipe gaskets, one right after the butterfly and the other where it connects to motor, if rpms change then u have an air intake leak at the gaskets.

but most likely carb needs a good cleaning and doubt that seafoam would resolve it, but doesnt hurt to try.

as for running it lean, not a great idea for long run time, but closing choke down a little should be ok for a quick snow removal job
 

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You should check your valves for correct clearance also.
I was just going to post the same thing. If the exhaust valve isn't closing fully, some burning fuel/air mixture will leak into the muffler every time the engine fires, which can make the muffler glow. This can damage the valve, as it will overheat.

Checking your valve clearances, and adjusting them if needed, would be a good idea. With an OHV engine, checking and adjusting them is fairly straightfoward.

"As for the Sea Foam, I've used it with cars but never a snowblower. Is the principle the same? Fill the tank with it?"

I have never simply added Seafoam as if it was gas. As in, don't just pour in a bottle of it into the tank, or you'd be running on a huge percentage of Seafoam vs gas. Check the bottle's instructions for the proper mix ratio.
 

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first deal w/the simple things, carb, fuel delivery, or air leaks.
he bought it used so most likely gummed up carb.
then check for valve issues. its a fairly new motor so highly unlikely.
imo
 

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Discussion Starter #13
Vinny, thanks for the reply. Is there a service manual at all for the carb on that Briggs engine?

Jonnied, why would you think the valves' clearance would need to be checked?

The history of the snowblower would lead me to believe that it's bad gas that has clogged the carb. The previous owner had switched to a snow clearing service and had only used the machine sporadically over the last year and a bit. As for how it was stored, I have no idea.
 

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Discussion Starter #14
RedOctobyr,

For sure, I mixed it according to SeaFoam's specs. I didn't just run it on SeaFoam!

If the kids stay asleep, my plan is to tackle the carb tonight, and check for other leaks along the intake system. If after that there is still some backfiring, then I will check the valves.

Thanks for your help!
 

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Discussion Starter #15
I don't know if it's best to start a new thread, or reply to this existing one. Since I've last posted, I've taken the carb apart and cleaned it; I've drained out all the old bad gas and replaced it with fresh; I've changed and correctly gapped the spark plug.

I have not yet checked the valve clearances (is there a reference out there for servicing this engine 12D105-0172-F8? I can't find any manuals online), and I have couldn't tell if there was a drop in RPM spraying carb cleaner near the gaskets. I will check this tomorrow.

The backfiring issue is still there, and on top of that the snowblower runs really rough off of choke (including backfires) and will die out.

Any help is appreciated.
 

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that's a lot of hunting against the governor there, sounds lean to me
that 12D105-0172-F8 engine is made by brigs almost most any brigs manual should help you
 

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I've taken the carb apart and cleaned it; I've drained out all the old bad gas and replaced it with fresh.
Can you explain in more detail the steps you took to rebuild the carb? Did you take it completely apart, use carb cleaner, compressed air, remove welch plug(s), use torch tips in the orifices, use ultrasonic cleaner and replace needle, seat, gaskets, welch plug(s), fuel filter, fuel lines, etc.?

Sometimes, a quick application of carb cleaner, torch tips and compressed air on the primary jet and/or idle mixture jet is all it takes. Other times you can spend considerable time doing everything listed above and still be unsuccessful.

As much as I hate to resort to being a parts swapper, a $12 Chinese carb is sometimes the best choice.
 

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(is there a reference out there for servicing this engine 12D105-0172-F8? I can't find any manuals online
Any help is appreciated.
Are you sure the choke plate is open when the engine is running bad? To me it sounds like the choke is closed when running bad and making an overly rich condition. Anyway, here is a link to the service manual, page-93 for valve adjustment which I don't think it needs.

https://drive.google.com/file/d/0B6NaqjIxWV1ybEN0LWo3azl6OUU/view
 

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My Powermax HD 826 (Briggs OHV) is very cold blooded. And runs/stumbles similar unless I continue to use partial choke for a couple minutes while it warms up. No Backfiring.

Does your 726 come out of this stumbling/hunting once it is thoroughly warmed up?
 
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