3 weed whackers, same problem

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  #1  
Old 06-20-08, 02:14 PM
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3 weed whackers, same problem

I've taken a fancy to playing with two strokes. A gentlemen gave three weed whackers that weren't working. Told me they were mine.

None would start when I got them. Cleaned them up. New fuel lines, fuel filter, cleaned gas tank using a little gas, removed carb and blasted with carb cleaner and blew out with air. The problem is they all start run for about 5-8 seconds and stop.

Of note is the fact they nearly start fully choked. Go to half choke and they all start but quit a few seconds later. Only starts again by repeating the order.

Is it a diaphragm or vacuum issue. Carb parts look pretty good to me. Don't think is high/low speed needle issue.

Any ideas. I am wondering if this is common problem and I am missing an easy fix I don't know about!
 
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Old 06-20-08, 05:56 PM
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They all need new fuel pumps. The diaphrams are shot. I've got the same thing sitting out in my shed and haven't gotten around to picking one up yet. The carbs are SO simple on these things, so you have to look for mechanical failures before you'll find carbon or varnishing most of the time. I think I ripped a forearm muscle trying to get mine started

Nice thing is, they all should have the same carb on them, take the same ratio of gas/oil and use the same trimmer line, so it shouldn't take much and you'll have a trimmer for yourself, and 2 to sell!
 
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Old 06-20-08, 05:58 PM
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before you spend any more money.

have you tried to run them with the mufflers off? A lot of 2 stroke small engines will clog up the muffler and they won't run.

If they run with the muffler off, take a propane torch and burn out the oil buildup of whatever it takes to get rid of the gunk in them.
 
  #4  
Old 06-20-08, 06:14 PM
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Thanks for the info.

I suspected possible diaphragm/fuel pump problem. That seems like the next logical step. The fact that it will start when primed and than dies means fuel starvation I'd think. However, read in another thread that if the needle isn't seating correctly, you'll get flooding.

The muffler, did try that with one of the whips and it didn't help, I'll try it with the others just to see.

I'll update when I get back to work on these things.
 
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Old 06-20-08, 07:28 PM
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I have a feeling your "fancy" with 2-cycle won't last long, what fixes one doesn't fix the next one. Frustration and 2-cycle are synonymous when it comes to fixing small trimmers. For carb info go to www. zamacarb.com then select the Aftermarket tab the same for www.walbro.com both have good carb info. Get a good bath type carb cleaner, I recommend NAPA mac 6402 and a air compressor or several cans of brake parts cleaner(doesn't leave residue) and have fun. Have a good one. Geo
 
  #6  
Old 06-21-08, 06:36 AM
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I am wondering why you have discounted the high/low needle adjustment. If they are way out of adjustment, it ain't gonna run. Most mfgrs these days think we are all idiots, and put some sort of protective cover over the screws, or require a special tool. Give it some thought, and you can get around this(I cut a slot with my dremel tool) Screw each all the way in(not too hard!), noting the number of turns. Screw each one out two full turns. This is a good starting place, and it should stay running. Fine tune from there. The screw closest to the choke is usually the high speed. Be careful about screwing them in too far, as too lean will burn up the engine. Err on the side of a little rich.
 
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Old 06-22-08, 12:40 AM
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I'd also look at the fuel line going to the clunk in the tank. I've seen it degrade and soften, which allows it to close up when the engine starts drawing fuel. Perhaps the previous owner used some sort of oil or additive that wasn't compatible with the tubing.
 
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