On Apr 20, 7:54*am, Manjo wrote:
On Apr 19, 10:40*pm, Oren wrote:





On Sat, 19 Apr 2008 07:33:17 -0700 (PDT), Manjo
wrote:

On Apr 18, 9:44*pm, Oren wrote:
On Fri, 18 Apr 2008 15:04:18 -0700 (PDT), Manjo
wrote:

On Apr 18, 12:22*pm, Manjo wrote:
On Apr 16, 10:30*pm, Manjo wrote:

I have a leaf blower that uses a 5 hp B&S "L" head engine. *The carb
is pretty simple with a choke butterfly, throttle butterfly, and
rubber diaphragm fuel pump. *The carb sits on top of the fule tank.
The carb has no bowl. *The governor linakges are clean and the
governor appears to be working fine.

The leaf blower was starting to run poorly last fall. *This spring it
started right up, but after4-5 seconds after running smoothly at
proper speed, it will slowly loose rpms and finally stop after 15-20
seconds.

I have cleaned the pick-up tube, replaced the carburetor diaphragm
fuel pump along with the gaskets between the carb and the fuel tank,
and the gasket between the carb and the engine. *I've also
disconnected the engine ground wire that normally kills the engine
when the throttle is tuned full off. *But after doing all this the
engine still will not stay running for more than 30 - 40 seconds..

Thanks in advance for any tips, suggestions, or coments.

Manjo

The engine starts, revs properly and then dies with the choke
partially or fully OFF about the same time. *Keeping the choke on full
kills the engine faster.

GROUP REPLY TO Don, Jeff, jp (might be a duplicate post)

A couple of days ago when I started working on this problem, the fuel
intake screen at the bottom of the intake tube in the gas tank had a
lot of junk in it. *I pulled the intake tube off the brass intake tube
and sprayed both with non-residue brake cleaner fluid and blew air
through the tubes both ways to clean them out.

Yesterday, I DID take the gas tank completely off the engine and used
filtered gasoline to flush the tank. *I swirled the gas in the tank
and then poured the gas from the tank into a funnel lined with a paper
filter. *The funnel/filter were feeding into a clean gas container. I
did this several times and I DID get A LOT more debris out of the
tank. *Most of the pieces were about 1/64th to 1/32nd of an inch..
Some stuff was black and other pieces were sand in color. *I’m
wondering if stuff is getting TEMPORARILY sucked up against the intake
screen killing the engine, then the debris drops back on to the bottom
of the tank when the engine dies???

There is no fuel line and no inline fuel filter other than the wire
screeen at the bottom of the intake tube. The carb fits directly on
top of and is bolted to the fuel tank and then the carb is bolted to
the engine. *There's no fuel line. *There's a nylon or plastic feed
tube from the carb into the tank. *There's also a small reservoir at
the top of the tank that looks like a idle feed tube with an intake
jet at the bottom that I believe feeds the carb's idle circuit. *I
blew compressed air through all the carb circuits yesterday, but TODAY
I will also spray Berryman’s carb cleaner through all the circuits
before putting everything back together.

I have the air filter off the carb and can see the entire choke
butterfly. *The butterfly arm sits in a slotted nylon detent that
holds the arm in place. *As far as I can tell, the butterfly is
staying firmly in place. *I don't have a tilting problem since the
carb has no carb bowl or float.

I have gotten the engine to run a second or two longer each time I
spray engine-starting fuel into the carb intake (at the choke
butterfly). *But even constantly spraying starter fluid into the carb
won’t keep it running. *I have not tried spraying gas into the carb
because I'm assuming the starter fluid is more condensed and more
volatile than regular gas.

I hope it is a fuel starvation problem and this will fix the dying
problem. *If it doesn't, then I'm going to replace the magneto.

Thanks for all the great tips and replies. *Please keep them coming if
you see I'm missing anything.

Manjo- Hide quoted text -

- Show quoted text -

Got it all back together and it ran just a bit better. *The engine
still runs fine for a few seconds and then start the same decline
until it stops.

I watched everything and it all seemed to function correctly. *I then
tried pressing down and twisting the spark plug cap and the engine
"seemed" to run a little longer at proper rpm, but it still died. *I
crimped the spark plug c0onnector and it ran a few seconds more, but
still died.

My current theory is there's a magneto or spark plug cable problem.
I'm going to try crimping the spark plug cap tighter and if that
helps, but doesn’t solve the problem, I'll take the magneto off the
engine and check it visually.

Does anyone know how to test a magneto? *My magneto is behind the pull
starter and cover combination, and to gain access to the magneto
requires removing the cover, but no way to hand starts the engine with
the recoil starter off the engine. *Right now, when I do an ohms test,
I get 2,500 ohms with one probe on the spark plug cap and the other
probe against the magneto body. *Does anyone know what voltage the
magneto is creating? *Can a standard voltmeter be set-up between the
spark plug and spark plug cap for a reading, or will the magneto blow
out the meter?

TIA for everyone's help.

Manjo

...(magneto) results in up to 10,000 V or more at the spark plug.

read this page..(Testing the magneto)

http://www.repairfaq.org/samnew/lmfa...htm-Hidequoted text -

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Great page. *I looked at my multimeter and it can only handle up to
1,000 DCV. *10,000 DCV would blow mine up.

Manjo

Do a "shade tree mechanic" (G) test. Pull the plug, re-attach the wire
on the plug *and *lay the plug on a good ground (scratch the paint) of
metal. Pull the start rope and watch the spark. You want to see a
bright blue spark and hear it snap.

(The other method is to hold the plug wire terminal in your hand give
'er a yank on the rope BTDT.

The flywheel has two magnets inside (not shown in your .pdf file).
They can become corroded and a simply cleaning with a fine sand paper
can clean them to a shine.

Magnetos do go bad, but very seldom in my experience.

Look on the last page at part #147 (Seal Needle Valve) and part #118
(adjustment screw), If one or both are damaged, you'll not get the
proper adjustment.

Examine the tip of the screw for damage or wear. Sometimes they bend
the tip of the screw if the tighten them down to far into the seat.

I'm throwing things out there, because I like/want to avoid pulling
the flywheel.

Now, have you hit anything last fall with the mower? The flywheel has
a shear pin. It can be a small fracture, but the timing is off on the
magneto...just a bit.- Hide quoted text -

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Good idea to clean the magneto. *I've been hesitant to remove the
magneto since it seems to be a pretty close fit to the rotor and I
didn't want to introduce another problem, but it's time now. *The
rotor itself has some light rust that I'll sand lightly, too.

I did a similar spark plug test a few days ago. *I left the spark plug
in the engine port and put another spark plug in the cap and held it
to the top of the first and I was able to start the engine. *Although
it ran a little slower rpm-wise, the engine functioned close to normal
and I could see a spark across the hand-help plug gap that looked
good. *As the engine slowed down, there was more yellow coloration to
the spark and then the engine died. *I will try this and your test
again just to be sure I’m getting a decent spark after I clean the
magneto and rotor.

I haven't chased the valve seat, but I did spray it with carb cleaner
and blew it out with compressed air. *I checked the idle adjustment
needle tip and it looked good: *it was straight and did not have any
apparent wear or damage to the tip.

I'll check all these things today.

Manjo- Hide quoted text -

- Show quoted text -

If spark is yellow its weak, it should be white to blue white,