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Snowblower engine needs choke to run smoothly



 
 
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  #1  
Old February 5th 11, 06:20 AM posted to alt.home.repair
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Posts: 2
Default Snowblower engine needs choke to run smoothly


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?




Ads
  #2  
Old February 5th 11, 01:13 PM posted to alt.home.repair
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Posts: 4,505
Default Snowblower engine needs choke to run smoothly

On Feb 5, 12:20*am, Taylor 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.

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?


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.
  #3  
Old February 5th 11, 01:59 PM posted to alt.home.repair
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Posts: 198
Default Snowblower engine needs choke to run smoothly

On Feb 5, 12:20*am, Taylor 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.

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?


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
  #4  
Old February 5th 11, 07:04 PM posted to alt.home.repair
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Posts: 13,945
Default Snowblower engine needs choke to run smoothly

On Sat, 05 Feb 2011 00:20:58 -0500, Taylor 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.

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?




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.

Spark Plug Chart:

http://www.verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm
  #5  
Old February 5th 11, 09:30 PM posted to alt.home.repair
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Posts: 682
Default Snowblower engine needs choke to run smoothly

In ,
Oren typed:
:: On Sat, 05 Feb 2011 00:20:58 -0500, Taylor
:: 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`


  #6  
Old February 5th 11, 10:55 PM posted to alt.home.repair
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Posts: 13,945
Default Snowblower engine needs choke to run smoothly

On Sat, 5 Feb 2011 15:30:02 -0500, "Twayne"
wrote:

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.


Agreed! I've _never_ seen a B&S engine that did not allow for
air/fuel mixture adjustment (since I was knee-high to a grasshopper).

OP: enter essential information here, find the link for the
machine/parts/exploded view and post it.

http://www.briggsandstratton.com/engines/support.aspx
  #7  
Old February 5th 11, 11:52 PM posted to alt.home.repair
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Posts: 2,030
Default Snowblower engine needs choke to run smoothly

?
"Oren" wrote

Agreed! I've _never_ seen a B&S engine that did not allow for
air/fuel mixture adjustment (since I was knee-high to a grasshopper).


Have you seen the newer engines? Many no longer have the two screws that
allow you to adjust the carb like days gone by.


From the Tecumseh manual, page 13 http://www.cpdonline.com/692509.pdf
A main or idle adjustment needle may be replaced by an
internally fixed jet on some models.
The main nozzle contains a ball check valve. The main
purpose of this ball check is to eliminate air being drawn
down the main nozzle during idle speeds and leaning the
idle mixture.

  #8  
Old February 5th 11, 11:53 PM posted to alt.home.repair
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Posts: 2,030
Default Snowblower engine needs choke to run smoothly

?
"Twayne" wrote

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.


http://www.cpdonline.com/692509.pdf
See page 13. No adjustment on many new carbs

  #9  
Old February 6th 11, 12:24 AM posted to alt.home.repair
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Posts: 13,945
Default Snowblower engine needs choke to run smoothly

On Sat, 5 Feb 2011 17:52:19 -0500, "Ed Pawlowski"
wrote:

?
"Oren" wrote

Agreed! I've _never_ seen a B&S engine that did not allow for
air/fuel mixture adjustment (since I was knee-high to a grasshopper).


Have you seen the newer engines? Many no longer have the two screws that
allow you to adjust the carb like days gone by.


From the Tecumseh manual, page 13 http://www.cpdonline.com/692509.pdf
A main or idle adjustment needle may be replaced by an
internally fixed jet on some models.
The main nozzle contains a ball check valve. The main
purpose of this ball check is to eliminate air being drawn
down the main nozzle during idle speeds and leaning the
idle mixture.


No. Never saw that before. Learned something today...

Maybe the OP will tell us if he has a Tecumseh carb on his B&S engine.
It would be interesting to know exactly what he has.

In any account he should not need to run his engine with the choke on.
  #10  
Old February 6th 11, 01:43 AM posted to alt.home.repair
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Posts: 2,030
Default Snowblower engine needs choke to run smoothly

?
"Oren" wrote
From the Tecumseh manual, page 13 http://www.cpdonline.com/692509.pdf
A main or idle adjustment needle may be replaced by an
internally fixed jet on some models.



No. Never saw that before. Learned something today...

Maybe the OP will tell us if he has a Tecumseh carb on his B&S engine.
It would be interesting to know exactly what he has.

In any account he should not need to run his engine with the choke on.


Many engines have that feature today to avoid the environmental police.
Yes, he should not have to put the choke on, but it may just be a linkage
adjustment to get the choke truly off. Can't tell from here.

 




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