On Dec 17, 2:39*pm, E Z Peaces wrote:
Jay Chan wrote:

There is an "Idle Mixing Needle" and the channel for it. *And I have
cleaned it and used compressed air to blow the channel. *Honestly, I
don't know if this matters or not because the problem that I have is
with running the engine in high speed; therefore, the idle mixing
needle should be irrelevant.

There's an idle mixing needle! *Great! *That should help troubleshooting.

When carburetor people talk about idle and high speed, they're really
talking about throttle opening. *You say the throttle is pretty well
closed, so the idle mixing needle should be the most important adjustment..

1. *Does turning the needle affect engine speed? *If not, it sounds as
if a channel is clogged.

2. *Can you turn the high-speed needle to where the manual suggests,
then adjust the idle mixing needle to run the engine with no choke? *If
you can, and that adjustment is reasonably close to what the manual
suggests, great! *No air leak!


The engine speeds up and slows down following the adjustment of the
idle mixing needle. I guess this means the channel related to the
idle mixing needle is not clogged. But adjusting the idle mixing
needle only has effect if the high speed mixing needle has opened 1/2
turn more than the manufacturer's suggested initial setting.
Otherwise, adjusting the idle mixing needle doesn't have any effect.

I have also tried setting the high speed mixing needle back to the
manufacturer suggested initial setting, and then trying to adjust the
idle mixing needle to see if I can run the engine with no choke. But
this doesn't work. Doesn't matter how I adjust the mixing idle
needle, the engine still needs to have some choke (at least 40 to 50%
choke). Even with 50% choke, the throttle valve is opening and
closing by itself frequently. The only way to make the engine running
without any choke and without having the throttle valve opening and
closing like crazy is to turn the high speed mixing needle 1/2 turn
more open than what the manufacturer has suggested (from 1-1/4 turn to
1-3/4 turn). This is as far as I can manage to achieve; still, the
throttle valve is mostly closed.

Having said this, I have a feeling that this may not be a problem for
three reasons:

1. The manufacturer suggested setting is just a initial setting. The
manufacturer expects us to adjust it. Therefore, the fact that I need
to keep the high speed mixing needle more open than what the
manufacturer has suggested as the initial setting may not mean that
there is anything wrong -- I think.

2. The fact that the throttle valve is mostly closed when the engine
seems to be running OK even under load may not mean much. The load
that I put on the engine is a "simulated" load, not real load. I am
just letting the wheels of the snow thrower and the snow throwing
mechanism free spinning. This "simulated" load may not be enough for
the engine to open the throttle valve. I will have to try this again
with real load when there is snow on the ground.

3. The engine sounds fine when I turn the lever in high speed with no
choke. This may mean that the engine is running at the correct rpm.
Having said this, I don't quite remember how the engine sound is
supposed to be -- afterall, this snow thrower has not run right for
two years. I will have to wait for the tachnmeter to use it to
confirm if the engine is running at the right rpm.

Therefore, I may not really have a problem -- that's after I have
cleaned the carburetor and adjusted the high speed mixing needle.


4. * What is the problem of running this snow thrower as is? *I mean
running it in full open choke, with the speed lever at high speed, but
the throttle valve is somehow closed. *Does this mean that the snow
thrower will run slow and cannot throw the snow to the proper
distance? *Sorry, I don't have any snow on the ground to test this.

If it's an air leak, the engine may run rich when the throttle stays
open to throw snow. *With the throttle open, the air leak would matter
less and the rich adjustment of the mixing needle would matter more.

If there is an air leak and the throttle stays open under load, the
engine should be running lean because of the extra air. *This may
explain the reason why the "engine-stall" problem goes away when I
open up the high speed mixing needle an additional 1/2 turn to add
extra fuel to the carburetor. *Is this what you are trying to tell me?

Suppose the throttle is closed and the leak adds 10% to the air the
engine gets. *That will make the mixture leaner. *If you open the
throttle to let 10 times more air through the carburetor and the leak
stays the same, it will be adding only 1% to the air the engine gets, so
it won't matter much.


OK, I understand what you mean. I just don't know how this is related
to my situation.
Thanks anyway.

Jay Chan