Weed Eater starts, but won't rev up?

Your muffler may be clogged. Where I am, mufflers seem to attract dirt daubers in the off-season, and their nests prevent the exhaust from exhausting. Oil can also turn to tar in a warm muffler.
Take off the muffler while the engine is cold. Don't misplace or damage any screws or rings in the process. Tap the body on a hard surface to loosen what may be inside. Rinse the muffler out from both directions. On a concrete surface, take a butane torch and begin evenly heating the muffler, allowing the flame to enter the muffler. Avoid burning any screen inside. If there's oil / tar built up, it will ignite and burn off. Repeat the heating until nothing burns off, then allow to cool and reassemble.
I've seen them so gunked up they'll burn for an hour.

Phil
August 2007

OK, I did not find a model number. It is an 18CC machine, Featherlite? I think. I found the muffler full of oil, and yes there is a screen inside the muffler. (A Spark Arrestor?) It is all carboned up and it isn't a screen anymore but more like a black pipe. I went to 4 places trying to find a replacement, no luck. Tractor Supply Company says they can order one. Meanwhile, I bought a can of Berrymans B12 and I am soaking the old screen. I put the Weed Eater back together, and it runs and is useable, but it is hard starting. I am wondering if the missing screen is causing a loss in compression.

You have to take the muffler off, it is held on with a spring on either side, much like a brake spring. The screen is cylindrical,
like a pipe going inside the muffler. I pulled it out gently, working slowly around the edge of the screen with a pair of long nose pliers.

As I said it now runs and has power, but it is hard to start.
The bad part of this job is you have to remove everything to remove the muffler from the engine. You must remove the hand grip/throttle assembly, front plastic housing, rear plastic housing, and loosen the clamp thats holding the shaft to the front housing. I think this is a common problem with string trimmers of all makes and models.

John
July 2007