[Shop-talk] string trimmer engine won't run

[Brian Kemp]

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