Snowblower engine needs choke to run smoothly

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My snow blower has a Briggs & Stratton 7.5 hp "Powerbuilt Snow" horizontal engine. It has always need a little choke to run smoothly after it warms up. With no choke it runs, but stumbles slightly. With one click it is a bit smoother, and with two clicks it runs the smoothest. More than that, there is too much choke and the engine will die.
Thinking that perhaps something is clogged in the carburetor/jet, I replaced the whole carb with a new one. The result is exactly the same.
I have fresh gas, use Sta-Bil, etc. I'm not overly worried about it, I just use two clicks of choke for best power.
However, I suspect that I'm not getting the full 7.5 hp with the choke restricting air intake. I'm also curious what the problem is. A repairman said that all engines are tuned lean due to EPA rules. Of course there is no way to adjust the mixture.
Any ideas what causes this? Is the repairman right about the mixture set overly lean on purpose?
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Ii assume this is one of the new carbs that isn't designed to be easily adjusted? The point about being set to run lean is interesting. I have a Sears two stroke blower and it too usually runs best with the choke set to half on. As soon as you move the choke to off, you can hear it slow down.
One way for it to be running lean, even with a new carb, is an air leak, eg between the carb and manifold, leaking head gasket, etc.
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If you feel that the carb is not the problem, the next thing to check (in order) would be manifold gasket, cracked manifold, head gasket, sticky exhuast valve ( carboned or gummed up not allowing it to close completely, or closes sluggishly).
Hank
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In wrote: :: ::: ::: My snow blower has a Briggs & Stratton 7.5 hp "Powerbuilt ::: Snow" horizontal engine. It has always need a little ::: choke to run smoothly after it warms up. With no choke ::: it runs, but stumbles slightly. With one click it is a ::: bit smoother, and with two clicks it runs the smoothest. ::: More than that, there is too much choke and the engine ::: will die.
Mal-adjusted choke position; no-choke is bringing it backwards, partly closing in the opposite direction. Watch the flapper work with air filter removed. Note: Tuning will be different with air filter removed so don't forget to account for that.
::: ::: Thinking that perhaps something is clogged in the ::: carburetor/jet, I replaced the whole carb with a new one. ::: The result is exactly the same.
Did you check for full fuel-flow from the tank to the filter and filter to the carb? Partial plug or kink in the hose can pinch off gas supply partly & make run lean.
::: ::: I have fresh gas, use Sta-Bil, etc. I'm not overly ::: worried about it, I just use two clicks of choke for best ::: power.
Empty tank & refill with fresh gas newly purchased. If this is last year's gas it could do that, especially if there is an over abundance of Stabil in the gas.
::: ::: However, I suspect that I'm not getting the full 7.5 hp ::: with the choke restricting air intake. I'm also curious ::: what the problem is. A repairman said that all engines ::: are tuned lean due to EPA rules. Of course there is no ::: way to adjust the mixture.
I suggest he's blowing smoke; that's still no reason to have the choke to any position but OFF when the engine has warmed up.
If it has a carburator and burns gasoline, there most definitely IS a way to adjust the mixture!! Check the carb documentation or the machine's paperwork.
::: ::: Any ideas what causes this? Is the repairman right about ::: the mixture set overly lean on purpose?
I think he just wanted you off the phone. Irrelevant to what you're having to do to keep it running right.
::: ::: ::: :: :: I'd check the air filter and be sure it is clean or new. :: Does it run better with the filter removed, not needing :: the choke... :: :: Also look at the spark plug. Adjust the plug gap a little :: (open or close it a tad) and see what happens or replace :: the plug. Make sure you have the correct/recommenced plug.
Better to check/adjust the plug gap to precisely what it is supposed to be. Usually it's 0.030" for that size B&S in my experience.
:: :: Spark Plug Chart: :: :: <http://www.verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm
Air filter, fuel filter (if you find water, also the gas tank), choke flapper needs adjust, lo-speed screw, low-oil shutoff, fuel line partly plugged, and so on.
Does it start easy and then run rough, or is it also hard to start? Stabil makes them hard to start, especially if excessive amount is collected in the carb. bowl.
HTH,
Twayne`
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?

http://www.cpdonline.com/692509.pdf See page 13. No adjustment on many new carbs
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On Sat, 5 Feb 2011 15:30:02 -0500, "Twayne"

Not neccessarily so. There is NO adjustable jet on that carburetor. It may or may not have a removeable/replaceable jet. The jet CAN be drilled to a larger size, but there will be no documentation in the manual to tell you how.

I WOULD go with a tank of fresh ethanol free fuel as a first step, if ethanol free fuel is a vailable in your area. If not, you could be stuck living with it or properly drilling out the jet.

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The last 5 or more years there is no adjustment provided. It is an EPA thing. Might be able to put on an earlier carb or modify the current one with old parts.
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Bigger hammer and electric drill.
nb
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Combined with ethanol in the gas, which causes a lean condition. Try running premium gas and see if that helps - particulatly shell premium if you happen to be in Canada. With Canadian Shell they put ethanol in the regular at up to 10%, which means up to 5% in mid grade and nothing in premium.
Works for me. Otherwise you will need to open up one of the fixed jets in the carb a bit. Not easy, but not impossible.
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Air filter being plugged would cause the OPPOSITE problem. You can be assured this is NOT the problem.
However, many engines are set up thet they NEED an air filter to be properly calibrated, and the vast majority of snow blower engines do NOT have an air filter (because it would very quickly freeze up, and there is very little free dust in the air when it is snowing/snowy

Again, very unlikely to be the problem. The plug will likely indicate it is running lean, but with unleaded gas, reading a plug is much less effective.
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Bingo! More likely, look for an air leak in the intake tract.

Howzabout some sorta moisture trap/thingie that could leak air? I know spit about snow blowers.

Reading a plug is incredibly effective. Just how lean, right down to engine destruction, can be determined. OTOH, if activating the choke is required, we already know it's running too lean. Again, I'd be looking for some sorta air leak.
nb
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On Sun, 06 Feb 2011 08:51:39 -0500, Stormin Mormon wrote:

For the slightly-larger B+S engines, checking the torque on the head bolts is part of the routine maintenance; they do sometimes loosen up. They're really heavy-duty gaskets and, as far as I can tell, designed to be re-usable - you can take the head off to inspect everything, clean up, and put the same gasket back on again. Unless, perhaps, someone's gooped it up with sealer ;-)
cheers
Jules
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On Mon, 07 Feb 2011 11:39:46 -0500, Stormin Mormon wrote:

No, seen it on old ones - very heavy-duty silver gaskets that don't seem to have compressed at all when removed. Taking the head off was also a routine maintenance thing, which makes me think they're supposed to be good for at least a few cycles.
All of the other gaskets on their engines are pretty thin in my experience and aren't intended to survive removal, but the head one's a real monster given the size of the engine.
cheers
Jules
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In :: wrote: :: ::: the vast majority of snow blower engines do ::: NOT have an air filter (because it would very quickly ::: freeze up, :: :: I've read that here before and can't figure why I keep :: banging my head on the wall ;-) :: :: Thanks
My Ariens have air filters; both of them. One is 20+ years, the other about 3 years. Neighbor's Sunbeam has one. They never plug even when it's pushed right in underneath the snow that's too deep for it. Once the engine starts to warm up, nothing is going to freeze anything shut. They're not very complex filters; just enough to keep junk from going in.
Others however don't have air filters. Whether that's most or a few, I don't know. Point is, statements should never be "always" or "all" or "never". On Ariens, the filter is part of the cover over the carb's air entry shroud.
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On Mon, 7 Feb 2011 14:22:39 -0500, "Twayne"

It is a screen fine enough to keep the squirrels from making a nest, and that is about it. I have an 8hp Briggs snowblower engine sitting in the garage and it has about 1/4 or 5/15 inch holes.
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Taylor wrote:

Thayne's suggestions about lack of fuel seem the most likely. Does it have a fuel filter? On-off for the fuel? Have you tried running it with the gas tank cap loose or off? Any chance of anything plugging the fuel outlet of the fuel tank?
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On 2/5/2011 10:43 PM, Dean Hoffman wrote:

Because it is a snow blower, there is no air filter. The carburetor is inside a "snow hood" which is designed to help it stay warm and prevent icing. There is nothing that I can tell is plugging the fuel outlet, and there is no shut off. I'll try running it with the gas cap off.
There are no adjustments on the carb either.
Thanks everyone!
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Ive never seen a snow blower with an air filter as others state they have, it would get wet and restrict air thats why they dont have them, an air filter will make it run richer needing less choke, not more.
How do you know the carb isnt just a poor rebuild, ive seen 6 bad starters in a row. It isnt getting enough fuel or it has an air leak at the manifold or maybe somethings cracked or loose letting in air. I would check the seal if the gasket and check everything. You could take it apart and run wire through the jets to see if they are actualy clean and blow it out with compressed air or put in in carb boil, or enlarge the main jet a bit, but be carefull. Ususaly needing a choke means you need a carb cleaning from old gas varnishing the jets, Ive a a bit of dirt logged in a passage do that and compressed air fixed it.
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In wrote: :: My snow blower has a Briggs & Stratton 7.5 hp "Powerbuilt :: Snow" horizontal engine. It has always need a little :: choke to run smoothly after it warms up. With no choke it :: runs, but stumbles slightly. With one click it is a bit :: smoother, and with two clicks it runs the smoothest. More :: than that, there is too much choke and the engine will die.
No, mine have filters. It's part of the can that covers the carb air intake and has the choke handle sticking out of it. They have never been plugged by anything. You must have heatless engines.
:: :: Thinking that perhaps something is clogged in the :: carburetor/jet, I replaced the whole carb with a new one. :: The result is exactly the same. :: :: I have fresh gas, use Sta-Bil, etc. I'm not overly :: worried about it, I just use two clicks of choke for best :: power.
:: :: However, I suspect that I'm not getting the full 7.5 hp :: with the choke restricting air intake. I'm also curious :: what the problem is. A repairman said that all engines :: are tuned lean due to EPA rules. Of course there is no :: way to adjust the mixture. :: :: Any ideas what causes this? Is the repairman right about :: the mixture set overly lean on purpose? : : Ive never seen a snow blower with an air filter as others : state they have, it would get wet and restrict air thats : why they dont have them, an air filter will make it run : richer needing less choke, not more. : : How do you know the carb isnt just a poor rebuild, ive : seen 6 bad starters in a row. It isnt getting enough fuel : or it has an air leak at the manifold or maybe somethings : cracked or loose letting in air. I would check the seal if : the gasket and check everything. You could take it apart : and run wire through the jets to see if they are actualy : clean and blow it out with compressed air or put in in carb : boil, or enlarge the main jet a bit, but be carefull. : Ususaly needing a choke means you need a carb cleaning from : old gas varnishing the jets, Ive a a bit of dirt logged in : a passage do that and compressed air fixed it.
It's interesting how some of the basics get ignored like the gas tank outlet covered with dirt or water, hoses plugged or kinked & not getting fuel TO the bowl in sufficient quantity, or even the float stuck (or sinking?) and so on. No one has even yet mentioned checking the bowl to see if it's filling or rate of output, all that easy kind of stuff.
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On Mon, 7 Feb 2011 14:29:12 -0500, "Twayne"

Funny, none of mine have EVER had filters and I've owned snowblowers for over 30 years, and worked on them for 10 years before that. ALL have had "heated air intake" shrouds.
Are your filters paper or foam elements? Got any part numbers? Possibly engines have been replaced with non-snow-blower engines(like tiller, edger, lawnmower, etc)

Most, except for the flow from the tank, would be addressed by replacing the carb - which the OP did. NOW - if he put a NON SNO BLOWER CARB on, it WILL run lean without an air filter.
And a SINKING cab float will NOT cause the engine to run lean and require choking to run when warm. Just stop and think about it for a second, or even a half second. A sunk float RAISES the fuel level in the bowl, causing flooding, rich running, dripping from the carb, etc................

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