Homelite Bandit SX 135 Trimmer - Tool Shed Forum - GardenWeb

First of all your SX135 comes with a Zama. Nothing wrong with Zama. Echo and Stihl both use them, and Stihl recently acquired Zama.

Usually complaints about Zama are because people took a ham-fisted approach to working on them. You can screw up a Walbro, Tillotson, or Mikuni just as easily.

You Homelite has an EPA mandated Emissions carb, meaning it has limiter caps on the Low and High Speed needles. These only allow you to adjust about 1/4 turn.

Sounds like you have a lean High Speed or Low Speed mixture. However, could also be clogged muffler.

Suggest you start by opening both mixture screws as far as limiter will allow. Screw closest to air cleaner is High Speed; closest to engine is Low Speed. If the 1/4 turn is enough to fix the problem, congratulations.

If not, then I'd clean carbon from muffler and the cylinder ports. You can be fairly rough with the muffler and not hurt it. However, only use an orangewood stick or popsicle stick to clean the ports. You don't want to scratch piston or cylinder.

If that doesn't help, you need to go back to carburetor. While you are not supposed to (EPA or CARB may be looking over your shoulder) you can cutoff the tabs on the limiter caps, permitting full rotation. I'd try a 1/2 turn on High speed jet, and 1/4 turn on Idle jet. If that still doesn't help, you need to tear down carb, remove all rubbers and plastics, soak in carb cleaner and reassembly using new kit (diaphragm, etc.). Initial setting for the two jets to tighten GENTLY, then back out 1 1/4 to 1 1/2 turns each.

Final adjustment is when warm, and correct when engine idles smoothly, accelerates without stumbling from idle, and runs at high speed just lean enough to prevent "four stroking". Do not be tempted to continue leaning High Speed to make engine scream. Err on the side of slightly too rich. Your engine will last a lot longer, although will be slightly "dirtier".