Fixing a Homelite trimmer--won't start

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  #1  
Old 07-24-10, 09:27 PM
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Fixing a Homelite trimmer--won't start

Hey folks, just got my 32-year-old Craftsman Eager-1 mower going after reading this site. Thanks!!!

Now I'm working on my trimmer. It's a Homelite ST-285BC (UT20581-3) with Walbro carb WT-220-3. I've got all the parts diagrams for trimmer and carb. Trimmer wouldn't run, had hardened fuel hoses and gummy carb when I got it.

Here's what I've done:
- Replace fuel lines and fuel filter
- Cleaned (w/carb spray cleaner) & rebuilt carburetor with kit:
- Cleaned out 3 low-speed holes & replaced Welch plug
- Cleaned out high-speed passage
- Cleaned needles, set 1.5 turns out from seated
- Replaced metering valve & set height (0.6-0.7" from carb face)
- Replaced metering diaphragm & gasket
- Replaced fuel pump diaphragm & gasket
- Replaced primer bulb
- Replaced gas!
- Checked compression, 125 psi
- Checked spark, looks good enough

The thing still won't start. The choke makes it run for just a few revolutions after the first pull; further pulls do nothing. After that, with the choke open, it will occasionally fire for a couple of revolutions at partial or wide open throttle on every third pull or so. No signs of firing at closed throttle.

Only strange thing I've found is on the priming system, when I pump the bulb, air bubbles come out of the return hose, seems it's never fuel. Is that normal?

Thanks for any ideas. This is my second 2-cycle engine after my Poulan chainsaw, which hasn't given me any trouble.
 
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Old 07-25-10, 12:55 AM
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Sounds kinda like it's flooding. Are the fuel lines connected properly? The return line should return gas and air.
 
  #3  
Old 07-25-10, 08:08 AM
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Does it have a spark arrestor in the muffler? You did not mention that you had cleaned it. If it is clogged, engine will not run.

Remove the arrestor and clean it with a blow torch.

Like previous poster indicated, the return line should return gas and a little bubbling when primer bulb is pressed several times.
 
  #4  
Old 07-25-10, 09:17 AM
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Woo hoo, fixed it!

I thought it was flooded too, but the spark plug was dry. I was about to give up on it, especially after reading all the people here saying that these trimmers are trash. It seemed like I was missing something obvious though, since the compression was very good, and the sides of the pistons looked very clean.

Well, last night I was reading around here and someone was talking about their exhaust screen being all loaded up. Took mine apart today, and while the screen looked 100% clean, the outlet pipe was 100% clogged with mud or something. Cleaned it out with a dental pick, primed it up, and bam, it ran! Took me a minute to set the mix and then I weed-ate the whole yard.

Thanks again DIY.com!
 
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Old 07-25-10, 10:24 AM
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Originally Posted by LawrenceC View Post
Does it have a spark arrestor in the muffler? You did not mention that you had cleaned it. If it is clogged, engine will not run. [...]

Like previous poster indicated, the return line should return gas and a little bubbling when primer bulb is pressed several times.
Hey LawrenceC, didn't see your post about the spark arrestor until just now. Wish I'd seen it earlier! I was just too focused on the carb.

I don't know why, it feels like it's all air going through the primer. If I pinch the return hose a little with my fingers I can feel the air going through, and as expected, nothing being sucked back. Yet the primer seems to work, so I won't worry.

Thanks for everyone's replies, I'm pretty stoked!
 
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Old 07-26-10, 11:45 PM
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Great! Good call LawrenceC!
 
  #7  
Old 07-27-10, 03:38 AM
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Thank you. I had a similiar experience with my string trimmer last year.
 
  #8  
Old 07-27-10, 08:00 AM
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clogged exhaust

I've got a similar trimmer. Around here we call them "mud dauber" bees. They plug up the small exhaust opening every year. The first time I was pulling my hair out trying to find the problem. Now I know right where to look! Glad you got it going
Steve
 
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