Troubleshoot my weed whacker

shawn

shawn

running dog lackey of the oppressor class
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Mar 13, 2005
Location
Raleigh, NC
I found a Stihl HT101 pole saw. It's basically a FS 100 weed whacker with a more aggressive business end. Put some fresh gas in it, replaced the clutch, fuel cap, primer bulb, etc, and got it to run. It's about 12ft long fully extended, cuts really well, seems super handy, so I figured it was worth some time and money to make a runner out of it.

It wouldn't idle reliably, would shut off mid-cut, was a pain to start, etc. I figured... 20 years old, unknown history, let's just start from zero and put a new OEM carb on it. Well, fuck me... throwing parts at it didn't solve anything. It'll start if you turn the choke on and give it just a little bit of throttle while pulling the string. If you keep braping the gas like a kid on a PW50, it'll kinda run. It sounds strong at full throttle, but it will shut off at any time for (seemingly) no reason. Next steps for me are to pull the muffler and the fuel pickup and look for issues there. I don't think it sounds like the ignition module (will restart immediately, doesn't shut off suddenly, etc), sounds more like fuel/air, but open to suggestions.

What say you?
 
On a serious note, did you replace the fuel lines? A cracked fuel line will let air into the fuel supply and throw off the ratio. Choking it helps mask the problem.
 
It'll run up to 40 minutes on a charge! Only pulls a 10" bar, too. I'd sooner (do what I've been doing and) drag a generator around on a trailer so I can use my HF chainsaw on a stick.
jeepinmatt said:
On a serious note, did you replace the fuel lines? A cracked fuel line will let air into the fuel supply and throw off the ratio. Choking it helps mask the problem.
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No, that's kinda what I'm thinking for next steps. The fuel lines to the carb are a little octopus deal with the tank gland, carb side lines, and pickup. They look fine, but I haven't looked that closely. There's a rubber line on the bottom side of the carb... pulse line, I think? Could that factor in? The new carb filled the prime bulb almost immediately. The old one was lucky to get it half full, so I'm thinking it's pumping just fine.
 
shawn said:
It'll run up to 40 minutes on a charge! Only pulls a 10" bar, too. I'd sooner (do what I've been doing and) drag a generator around on a trailer so I can use my HF chainsaw on a stick.
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40 minutes is a pretty decent time when each cut only lasts 10 seconds.
And since we're already down this path a little, there's another option that will run all day, and is lighter, and potentially more reliable...
notchequipment.com

Notch 20' Nobasu 4 Section Telescoping Aluminum Polesaw

jeimi.woffinden@zaneray.com
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I've had the 16ft version for going on 8 years and it still cuts just as well as day 1. But for stuff over about 3-4", the motorized version gets the nod. But if I'm just knocking off sub-2" limbs, I'll use the manual saw time and again because its so much lighter and easier to maneuver. I've cut 6" oak and pine limbs with it, but that is too slow and exhausting (and likely to pinch and bind the blade if you're too steep of an angle).
 
Spark arrestor screen cleaned up? People who run them half throttle plug up the screen. You can remove the screen to see if it works, but according to the man it must be installed or you can be fined.
 
No air filter or spark arrestor, but good ideas.
 
shawn said:
Put some fresh gas in it, replaced the clutch, fuel cap, primer bulb, etc,
Click to expand...
Did the "etc.," include a new fuel filter in the tank? I also vote for new fuel lines.
Also the "Insulator" which is between the carb and the head can become clogged or damaged from overheating. Make sure all passages flow with air.
 
shawn said:
No air filter or spark arrestor, but good ideas.
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Sure you know this- and not 100% how you mean the above - but if it’s designed with an air filter and there isn’t one in place it can prevent running as well by providing too much air and leaning out the mixture.
 
Ron said:
Sure you know this- and not 100% how you mean the above - but if it’s designed with an air filter and there isn’t one in place it can prevent running as well by providing too much air and leaning out the mixture.
Click to expand...
And could affect the vacuum that manipulates the little flappy thingys in those tiny carbs.
 
Has an air filter now. New fuel filter, new fuel lines, no change.
 
shawn said:
Has an air filter now. New fuel filter, new fuel lines, no change.
Click to expand...
Not being a smartass, this is why I sold my BR600 backpack blower and FS85 trimmer and went to battery stuff. If I didn't use them a couple times a month, they would run shittily and I would clean the carb a few times with no success and then magically I would do something (clean carb, change plug, try different fuel, turn left out of my driveway instead of right) and they would start running good again.
 
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