Sounds to me like the diaphragm in your carb has torn. I've had this happen
a few time ons 2-strokes about this age. The diaphragm acts as a fuel pump
using the pressure pulses from the crankcase to pull fuel from the tank. A
carb rebuild kit will include a new one.
Ben.....
On Thu, Mar 25, 2010 at 12:21 AM, Brian Kemp <bk13@earthlink.net> wrote:
> List,
>
> Last week my Homelite 2 stroke string trimmer stopped running and I'm after
> recommendations for things to check to get it running again. It is a
> straight shaft, 15142-R, which I believe is a reconditioned ST1725SR. It is
> about 10 years old, but mostly worked well over the years. The same model
> sold at Home Depot and Lowes for $109 at the time. I definitely got my
> money's worth, so won't be heart-broken if I can't get it running again.
> I used the trimmer with the stock string head around the yard then
> installed a Shakespeare Heavy-Duty Brush Cutter (
> http://www.lowes.com/pd_79979-42694-14872_0) in place of the string since
> I needed to cut more than a few weeds going into the canyon. I do not
> recommend this cutter since you will be spending $8 for replacement blades
> any time you hit the ground or something heavier than a weed.
>
> I had new gas and mixed the oil as I've done for years. After about 10
> minutes of use with the brush cutter, suddenly the trimmer lost power and
> stalled. I found I could go to full choke, pull the cord, then go the half
> choke and pull the cord and have it run normally for a few minutes. No
> choke and it died. Once I hit a heavy patch of brush, it would loose power
> and only idle. If I pulled the throttle it would stall. I repeated this
> several times, with a shorter run period each time till I couldn't make the
> engine run. Aside from the muffler area, the engine didn't feel all that
> hot when I got it back to the garage.
>
> The fuel hose was replaced a year ago and looks in good shape. The foam in
> the air cleaner was a bit dirty, so I cleaned it. The carb looked like new.
> The spark plug was fine. I cleaned the mesh spark arrester on the muffler
> exit as it was pretty dirty. I drained the fuel and looked at the in tank
> filter and it looked good. Pushing the primer bulb gives the normal
> behavior of getting firm after 6 pushes, so I don't think there is any fuel
> delivery problem. There are two adjustment screws on the carb, but since
> they have not been touched in 10 years, I wouldn't expect they moved. I
> learned from my Triumphs that you don't play with carbs if they were
> working.
>
> After this, I tried again with the stock string head back in place, but it
> would only idle at half choke. Turn off the choke and it died. Give it gas
> and it died.
>
> One of my thoughts is that the cutter head damaged the trimmer shaft. The
> brush cutter was a bit more rotational mass and quickly became a bit out of
> balance when the cutter blades became bent or bits of the plastic came off.
> Long thick grass also got wrapped up in the head and significantly loaded
> down the trimmer, requiring me to shut it off and clean out the grass. Will
> damage here cause the trimmer to stall when the throttle is pulled or the
> choke is in run position?
>
> Thanks for any advice,
>
> Brian
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