I wonder if there are any 2-stroke carburetor dudes out there who
could shed a little light on my situation:
I have a 2-stroke Weed Eater string trimmer that I've owned for quite
a few years. It has started and run flawlessly over the years, with
nothing needed from me other than filling the gas tank occasionally.
But this year, it suddenly wouldn't start. Being a cheapskate (and
loving to tinker) I disassembled the unit to try to determine the
problem. During my tinkering I discovered that if I poured a few
drops of gas/oil mixture down the carb throat, it would start and run
for a few seconds, so I decided it was a carburetor problem. I tried
pumping the primer bulb and that's when I realized that it wasn't
filling with fuel as it normally did.
After studying the design for a few minutes, I concluded that the way
priming works was as follows: the carburetor has two hose nipples on
one side of it. One hose connects to the priming bulb, the other
connects to the gas tank. A third hose runs between the gas tank and
priming bulb. When you pump the bulb, a vacuum is created in the hose
leading from it to the carburetor. That vacuum travels through the
carburetor internals, and out of the second hose nipple, connected to
the tank. As one continues to pump the primer bulb, this vacuum draws
fuel out of the tank and sucks it into the carburetor through the
second nipple. The fuel travels around inside the carburetor
("priming" it) and is eventually drawn out of the first nipple leading
to the primer bulb. The fuel enters the bulb and from there is pumped
back into the tank. This forms a sort of loop: as you pump the
primer, fuel travels down from the tank, into the carburetor, back out
of the carburetor through the other nipple, out to the priming bulb,
where it is pumped back up to the tank again. Does this sound right?
When I disconnected the hoses from the carburetor, the one leading to
the primer popped (indicating a vacuum), while the hose to the tank
squirted out gas (indicating a pressure build-up in the tank.) These
two facts led me to the conclusion that my carb was clogged.
I found a replacement on the web, ordered it and installed. Pumping
the primer then caused it to fill up with gas as it used to, and the
unit started right up. After a couple small adjustments it was
running like new. I was delighted and (a little too) proud of myself.
But then on the third use, I couldn't get it started again. I
disassembled it again, only to find the same symptom (no gas getting
"through" the carb) so now it seemed my brand new carb was clogged
How far off base am I???