On Sat, 05 Feb 2011 10:04:22 -0800, Oren wrote:

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...


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

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
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.